Journals >Chinese Journal of Lasers
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2011
Volume: 38 Issue s1
83 Article(s)
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Research Article
Design of Corneal Contact Lens by Wavefront Technology
Li Rui, Wang Zhaoqi, Liu Yongji, and Kong Xiangming
The design method of wavefront corneal contact lens by the objective optometry is presented. The back surface profile of the contact lens is acquired from the topographic data of the anterior corneal surface, via a fitting procedure of least square; and the front surface profile is acquired from the ocular aberrated waThe design method of wavefront corneal contact lens by the objective optometry is presented. The back surface profile of the contact lens is acquired from the topographic data of the anterior corneal surface, via a fitting procedure of least square; and the front surface profile is acquired from the ocular aberrated wavefront data, via a propagation procedure through tear film and lens medium with the diffraction theory of angular spectrum. Applying the profile of the two surfaces, the prescription of the contact lens can be obtained. Eight myopic eyes with different defocusing and astigmatism are selected in this research and their corresponding contact lenses based on the wavefront aberrations have been designed. By analyzing the vergence of the designed contact lens, it is found that the vergence of the contact lens is equal to that of the eye plus to that of the tear lens while the profile of the back surface of the contact lens is spherical and the vergence of the contact lens is equal to that of the eye for the case of toroidal, then the design procedure of the contact lens is validated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116001 (2011)
An All-Reflective Optical System for the Modulation Transfer Function Measurement of Near-Infrared Focal Plane Arrays
Xu Zhonghua, Wang Jing, Zhao Longcheng, Wang Peigang, and Fang Jiaxiong
To measure the modulation transfer function (MTF) of near-infrared InGaAs focal plane arrays (FPA), an all-reflective Offner optical system is designed and fabricated, which consists of two co-axial spherical mirrors, operating as a 11 imager with F/#=4. After optimization at the FPA working wavelength 1.7 μm, a nearlyTo measure the modulation transfer function (MTF) of near-infrared InGaAs focal plane arrays (FPA), an all-reflective Offner optical system is designed and fabricated, which consists of two co-axial spherical mirrors, operating as a 11 imager with F/#=4. After optimization at the FPA working wavelength 1.7 μm, a nearly diffraction limited field of view (FOV) up to 8 mm×30 mm is obtained. The MTF at a space frequency of 20 lp/mm (referring to the 25 μm×25 μm device′s Nyquist frequency) is above 0.8 in the FOV. After fabrication and calibration of the optical system, a Zygo interferometer is used to check its performance, finding that the root mean square (RMS) of wavefront error is about 1/20 wave at 0.6328 μm, and the MTF@20 lp/mm (0.6328 μm), is above 0.93. Then the measured wavefront data is inputted into CODEV to calculate the MTF at 1.7 μm. The result shows that, the value of MTF @1.7 μm,20 lp/mm is still above 0.8..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116002 (2011)
Increasing the Efficiency of CCOS by Local Deconvolution Algorithm
Li Ruigang, Deng Weijie, and Yan Feng
The convergent efficiency of computer-controlled optical surfacing (CCOS) relates to many factors such as algorithm, parameter settings, tool and abrasive. A kind of local deconvolution algorithm with high efficiency is put forward, firstly plotting the error figure to manufacturing area and non-manufacturing area, andThe convergent efficiency of computer-controlled optical surfacing (CCOS) relates to many factors such as algorithm, parameter settings, tool and abrasive. A kind of local deconvolution algorithm with high efficiency is put forward, firstly plotting the error figure to manufacturing area and non-manufacturing area, and programming the manufacturing trace in each manufacturing area, then doing deconvolution in local area along the manufacturing path, thus getting the dwell time of the tool in each area, lastly according the nearest point criterion to switch from one manufacturing area to the other. The ratio of the efficient manufacturing time to the total running time of the tool is raised greatly, so the whole manufacturing efficiency is increased, and the mid-frequency error is restricted to some extent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116003 (2011)
Magnetic Medium Assistant Polishing Technology
Deng Weijie, Zhang Feng, and Li Ruigang
In this paper, a novel magnetic medium assistant polishing technology and device is researched to complete the finish step of the optics. As the device working, the magnetic powder arranged with the magnetic field distribution. The magnetic powder became a flexible brush. The magnet wheel working with a high rolling veIn this paper, a novel magnetic medium assistant polishing technology and device is researched to complete the finish step of the optics. As the device working, the magnetic powder arranged with the magnetic field distribution. The magnetic powder became a flexible brush. The magnet wheel working with a high rolling velocity and the polishing liquid with abrasive is injected to contact region. The magnetic powder flexible brush is reforming with the magnetic field all the time, so the removal tool of the fabrication is invariable. The design and manufacture is finished and the device was connected to the CNC machine and experiment is completed to get the removal function, and roughness with K9 glass. The technology could be used in the practical fabrication..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116004 (2011)
Analysis of the Effect of the Large-Aperture Mirror Mount Parameters on its Dynamic Response
Zhang Junwei, Chen Wei, Zhou Yi, Chen Liangming, Zhou Hai, and Lin Donghui
In the inertial-confinement fusion (ICF) driver, the large-aperture array mirror mount is an important opto-mechanical system, which affects the beam direction and position precision. Random vibration and the parameters of the large aperture array mirror mount are the main factors that influence the dynamic response ofIn the inertial-confinement fusion (ICF) driver, the large-aperture array mirror mount is an important opto-mechanical system, which affects the beam direction and position precision. Random vibration and the parameters of the large aperture array mirror mount are the main factors that influence the dynamic response of the mirror. The finite element analysis software is used to analyze the relation between the parameters of the excited power spectral density (PSD), the structure elastic modulus, the damp ratio and the structure dynamic response. The results indicate that reducing the excited PSD and increasing the elastic modulus has the same effect on reducing large-aperture mirror mount structure dynamic response, and increasing the damp ratio is the best way. However, the effect of all the methods as reducing excited PSD, increasing elastic modulus and damp retio is becoming weaker..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116005 (2011)
Research on Tolerance Distributon of Wavefront Coded System Based on MTF Stmilarity
Yan Feng
Wavefront coding technology (WFC) is a kind of joint optical-digital imaging technology, which can extend the depth of focus (DOF) of optical systems and control the defocus and defocus related aberrations. Another important character of the WCT is to enlarge the error budget of optical systems. The modulation transferWavefront coding technology (WFC) is a kind of joint optical-digital imaging technology, which can extend the depth of focus (DOF) of optical systems and control the defocus and defocus related aberrations. Another important character of the WCT is to enlarge the error budget of optical systems. The modulation transfer function (MTF) invariance is defined in this paper and the comparison of MTF invariance among original system, wavefront coded system with original tolerance and wavefront coded system with new tolerance is presented. The new tolerance of wavefront coded off-axis three mirror anastigmatic system is presented according to certain criteria and the application of WCT is validated quantitatively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116006 (2011)
Design and Analysis of a Novel Actuator Topology of Deformable Mirrors
Chen Xindong, Zheng Ligong, and Zhang Xuejun
The deformation of a continuous facesheet DM with discrete push-pull actuators in the thin plate approximation is described by the differential equation. Analysis of the equation shows that to achieve a high quality correction of low-order aberrations, deformable mirrors should have some actuators positioned outside thThe deformation of a continuous facesheet DM with discrete push-pull actuators in the thin plate approximation is described by the differential equation. Analysis of the equation shows that to achieve a high quality correction of low-order aberrations, deformable mirrors should have some actuators positioned outside the correction aperture. By finite element analysis, the correcting abilities of defocus, astig and coma are compared. A novel design of 9 actuators positioned on the edge of aperture and mirror is proposed and optimized. The analysis results show that the new design improves the correcting abilities, especially for coma which is hard to correct. Finally the wavefront correction and modal correction methods are compared..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 116007 (2011)
Polarization-Based All-Optical Logic Gates Employing Electro-Optic Effect in Periodically Poled LiNbO3
Zhang Yinxing, Chen Yuping, and Chen Xianfeng
A simple approach based on polarization to process binary all-optical logic signal with validation is proposed, by electro-optic Pokels effect. In experiment, we choose optical signal with two orthogonal linear polarization states to present logic 1 and 0. This approach can alter the polarization state of input opticalA simple approach based on polarization to process binary all-optical logic signal with validation is proposed, by electro-optic Pokels effect. In experiment, we choose optical signal with two orthogonal linear polarization states to present logic 1 and 0. This approach can alter the polarization state of input optical signal about 90°on the polarization plane based on electro-optic modulation of periodically poled lithium niobate (PPLN). Optical signal can be switched between the two orthogonal polarization states, and polarization direction will be not changed without external applied electric field. Therefore, it can realize controllable-NOT function. If we choose external applied electric field to present logic 1 and 0, it can realize NOR and XNOR functions. In this approach, digital logic signal is carried on the polarization state of optical signal. The dissipation of intensity of optical signal is very small in this process, so this approach is more advantageous for multiply cascaded systems ,comparing with traditional approach ,in which digital logic signal is carried on the intensity of optical signal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 117001 (2011)
Biomedical Photonics and Laser Medicine
Study of the Effect of Saturated Light Intensity of LED Monochromatic Light on Growth of Prorocentrum Lima and Skeletonema Costatum in Red Tide
Miao Hongli, Sun Lina, Tian Qingzhen, and Zhou Xiaoguang
Light is one of the precipitating factors of red tide, and the intensity of light plays a key role on the growth of red tide advantage algae. Monochromatic LEDs are used as the light source to cultivate dinoflagellate Prorocentrum lima and diatom Skeletonema costatum. When temperature and light cycle are fixed, to inveLight is one of the precipitating factors of red tide, and the intensity of light plays a key role on the growth of red tide advantage algae. Monochromatic LEDs are used as the light source to cultivate dinoflagellate Prorocentrum lima and diatom Skeletonema costatum. When temperature and light cycle are fixed, to investigate the effect of different light intensities of green, red and blue light on the growth rates and spectrum absorption coefficient of algae is investigated. The results show that the saturated light intensity of blue light of Prorocentrum lima and Skeletonema costatum are the lowest, and the saturated light intensities of red light of Prorocentrum lima, and green light of Skeletonema costatum are the highest, respectively. Within saturated light intensity and the same light intensity, the growth rates of Prorocentrun lima and Speletonema constatum are the largest in blue light, but lowest in red and green light, separately. Besides, it is concluded that the growth rates of two algae are positive to the spectrum absorption coefficient, while saturated light intensity is negative to the spectrum absorption coefficient under different monochromatic lights..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 104001 (2011)
Polarization Scattering Imaging of Cancerous Tissue
Li Dongzhi, Liao Ran, Yun Tianliang, He Yonghong, and Ma Hui
Base on two cancerous samples various polarization parameter images are obtained by using three kinds of polarization imaging methods. It is analyzed that different polarization parameters′ character capabilities in different cancerous tissues and normal tissues. The results show that the polarization method can be appBase on two cancerous samples various polarization parameter images are obtained by using three kinds of polarization imaging methods. It is analyzed that different polarization parameters′ character capabilities in different cancerous tissues and normal tissues. The results show that the polarization method can be applied to the detection of cancer. According to the physiological and optical properties of cell, the Monte-Carlo simulation using simple scattering model is carried which agrees the experiment results and shows the potential of polarization imaging in the detection of cancer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 104002 (2011)
Monitoring Traumatic Brain Injury by Using Functional Near-Infrared Spectroscopy
Xie Jieru, Qian Zhiyu, Deng Ningkun, Yang Tianming, Li Weitao, and Hu Guangxia
Functional near infrared spectroscopy (fNIRS) technology is utilized to monitor brain tissue of rat model of traumatic brain injury (TBI). The reduced scattering coefficient of the local cortex of rats is monitored and recorded in vivo and real time by the fNIRS system. Brain water content (BWC) is measured by the wet Functional near infrared spectroscopy (fNIRS) technology is utilized to monitor brain tissue of rat model of traumatic brain injury (TBI). The reduced scattering coefficient of the local cortex of rats is monitored and recorded in vivo and real time by the fNIRS system. Brain water content (BWC) is measured by the wet and dry weight method. Intracranial pressure (ICP) is measured invasive ICP monitor. Imaging data of rat model is detected by small animal magnetic resonance imaging (MRI). Experimental results show that, there exists positive correlation between parameters and BWC, and ICP, the occurrence and development of cerebral edema can be detected earlier with the sensitive indicator of scattering coefficient..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 104004 (2011)
Holography and Information Processing
Speckle Noise Reduction in Digital Holography by Slightly Shifting Object
Pan Feng, and Xiao Wen
As a coherent digital holographic imaging method, the speckles noise degrades the image quality. To solve this problem, a method to reduce speckle noise is proposed for digital holography. A series of digital holograms is obtained by shifting object slightly. Each hologram is reconstructed individually, while the diffeAs a coherent digital holographic imaging method, the speckles noise degrades the image quality. To solve this problem, a method to reduce speckle noise is proposed for digital holography. A series of digital holograms is obtained by shifting object slightly. Each hologram is reconstructed individually, while the differences between these retrieved complex amplitudes due to the object shifting are corrected with phase compensation and image registration algorithms. So all reconstructed complex amplitudes of object have same distribution, but uncorrelated coherent noise patterns. The speckle noise is well suppressed by averaging these reconstructed images. The theory and experimental results prove that the method is effective and feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 109001 (2011)
Study on the Stereo Depth of Integral Imaging Three-Dimensional Display System
Wang Fang, Li Da, Zhao Xing, Yang Yong, Fang Zhiliang, and Yuan Xiaocong
In connection with the characteristics of integral imaging three-dimensional display, the stereo depth of integral imaging three-dimensional display system has been calculated using the cognominal-points spacing in the adjacent elemental images. Through in-depth analyze the maximum and minimum stereo depth reproduced bIn connection with the characteristics of integral imaging three-dimensional display, the stereo depth of integral imaging three-dimensional display system has been calculated using the cognominal-points spacing in the adjacent elemental images. Through in-depth analyze the maximum and minimum stereo depth reproduced by the system, the reconstructing ability of stereo depth is presented. The results show that the lens array pitch and cognominal-points spacing have important influence on the stereo depth, and then the reconstructing ability of stereo depth in the integral imaging system is determined by the resolution of display device and the lens array pitch. On the basis of theoretical analysis, modulation of the stereo depth of system is realized with optical experiments through changing the cognominal-points spacing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 109002 (2011)
Extract Spectral Feature Bands of Pseudoperonospora Cubensis′s Narrow-Band Multispectral Images Using Brightness
Feng Jie, Li Hongning, Liu Wei, Zhu Yundong, and Wu Shaoxian
In order to extract spectral feature for achieving spectral classification, 16 multispectral images of pseudoperonospora cubensis for cucumber disease, including visual light band, near-infrared band and a panchromatic band, were captured for 6 samples in this paper. Then, the distinguish ability of all multispectral iIn order to extract spectral feature for achieving spectral classification, 16 multispectral images of pseudoperonospora cubensis for cucumber disease, including visual light band, near-infrared band and a panchromatic band, were captured for 6 samples in this paper. Then, the distinguish ability of all multispectral images were computed by average gray, standard error and background gray. We ordered the 16 bands using the distinguish ability to 6 samples. The bands with high distinguish ability were extracted as spectral feature bands of cucumber′ pseudoperonospora cubensis. The result showed that it was speedy to extract spectral feature of cucumber disease by the gray of images. The multispectral images of 700, 600, 589 and 546 nm bands have plentiful black-white distribution and good contrast. They were spectral feature bands of cucumber′ pseudoperonospora cubensis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 109003 (2011)
Wavelength-Selective Imaging in Volume Holographic Imaging Systems
Wu Jiangtao, Jiang Zhuqing, Song Lei, Wang Yujia, Jia Ye, and Tao Shiquan
In this paper, imaging characteristics with different light sources based on volume holographic imaging system are researched. The volume holographic lens as imaging lens is recorded in the 2-mm-thick LiNbO3FeCu crystal at wavelength of 532 nm. The imaging characteristics of the imaging system are researched at the reaIn this paper, imaging characteristics with different light sources based on volume holographic imaging system are researched. The volume holographic lens as imaging lens is recorded in the 2-mm-thick LiNbO3FeCu crystal at wavelength of 532 nm. The imaging characteristics of the imaging system are researched at the reading wavelength of 532 nm and 640 nm. The results show that the depth resolution of volume holographic imaging system is different when different reading wavelengthes are used. Axial selectivity is more sensitive when the red light is used as the reading light. The imaging features of monochromatic light source and broadband light source are compared. Experimental results show that using broadband light source can obtained more transveres information of the object..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 109004 (2011)
Three-Dimensional Imaging for Micro-Optical Component by Using Dual-Wavelength Digital Holography
Wang Yujia, Jiang Zhuqing, Wang Zhe, Cheng Guofeng, and Wu Jiangtao
The three-dimensional (3D) profiles of a plate with many micro grooves is obtained by using dual-wavelength digital holography. Two individual phase images are obtained by using two different wavelengths, respectively, and the phase image for beat wavelength is obtained after dual-wavelength phase unwrapping. Then the The three-dimensional (3D) profiles of a plate with many micro grooves is obtained by using dual-wavelength digital holography. Two individual phase images are obtained by using two different wavelengths, respectively, and the phase image for beat wavelength is obtained after dual-wavelength phase unwrapping. Then the 3D profiles can be obtained through the phase image of the beat wavelength. This method is demonstrated by both numerical simulation and experiment. In the experiment, two lasers of the different wavelengths 632.8 nm and 671 nm are used to obtain a larger beat wavelength. The object is a plate with many micro grooves. The result shows that the average depth of the groove is 7.1 μm. This is in good agreement with the result given by the profilometer. It demonstrates that the 3D imaging result by using dual-wavelength digital holography is effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 109005 (2011)
Laser Manufacturing
Effect of Heat Treatment Austenitic Stainless Steel on Microstructure and Property of Laser Cladding Ni-Based Composite Coatings
Liu Hongxi, Zeng Weihua, Jiang Yehua, Zhang Xiaowei, and Wang Chuanqi
Ni60CuMoW+1.00%Ti alloy powder laser cladding composite coatings was fabricated on 1Cr18Ni9Ti stainless steel surface with normalizing treatment by 6 kW transverse-flow CO2 laser apparatus. The clad coatings was examined and tested for chemical composition, microstructure feature, phase structure, microhardness, corrosNi60CuMoW+1.00%Ti alloy powder laser cladding composite coatings was fabricated on 1Cr18Ni9Ti stainless steel surface with normalizing treatment by 6 kW transverse-flow CO2 laser apparatus. The clad coatings was examined and tested for chemical composition, microstructure feature, phase structure, microhardness, corrosion behavior and metallography by X-ray diffraction (XRD), microhardness test, electrochemistry workstation and optical microscopy (OM), respectively. The results show that some new phases are formed in the cladding layer which consist of γ-(Fe, Ni) solid solution, intermetallic compound NiCu, CrNiFeC, CuNiTi2, Mo9Ti and harden phase Ni2Si, Fe3Ni3B, WC, TiC. OM observation displays that the microstructure of cladding layer is homogeneous, compactness and forming a good metallurgical bonding interface. Micro-hardness measurement exhibits that the highest hardness lies in 0.5~1.0 mm range from the surface and reaches 649 HV. Electrochemical corrosion test in 5.0% NaCl saturated solution indicates that the self-corrosion potential (Ecorr) of composite coating sample increases by 192.8 mV and the corrosion current density (Icorr) decreases by 26.8%. Compared with the substrate and the composite coating, the corrosion resistance of stainless steel with normalizing samples improved significantly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 103001 (2011)
Influence of Nanosecond Laser Surface Modification on the Femtosecond Laser-Induced Damage of Ta2O5/SiO2 Dielectric Film
Chen Shunli, Zhao Yuan′an, Gao Pengpeng, Li Dawei, He Hongbo, Shao Jianda, and Fan Zhengxiu
The influence of nanosecond laser surface modification on the femtosecond laser-induced damage of 800 nm Ta2O5/SiO2 dielectric film is investigated in this paper. Surface modification of samples is performed by Raster-scanning with scanning mode of 1-on-1 and scanning velocities timed such that there is a beam overlap The influence of nanosecond laser surface modification on the femtosecond laser-induced damage of 800 nm Ta2O5/SiO2 dielectric film is investigated in this paper. Surface modification of samples is performed by Raster-scanning with scanning mode of 1-on-1 and scanning velocities timed such that there is a beam overlap at 70% of the peak fluence by 5 Hz-1064 nm-12 ns NdYAG fundamental lasers. Femtosecond laser damage of samples is carried out by 1 kHz-800 nm-135 fs Ti: sapphire laser system with 1-on-1 mode test. The result indicates the femtosecond laser-induced damage thresholds (LIDTs) of all the samples with various modification fluence steps are reduced by about 20%, which seems to be closely related with the contribution of the microscopic electronic defects (native or laser-induced trapping states) in the band gap..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 103002 (2011)
Integration Optimization of Laser Shock Peening Parameters Based on Numerical Simulation
Fan Jinrong, Huang Shu, Zhou Jianzhong, Wang Wei, Fan Yujie, Gao Bin, Zhu Wei, and Xu Zengchuang
In order to investigate the influence of different laser shot peening (LSP) parameters on the strengthening effect, the finite element software ANSYS integrated with ISIGHT was adopted to establish a LSP parameterized file. Multi-island genetic algorithm (MIGA) was applied to optimize the process parameters of LSP, andIn order to investigate the influence of different laser shot peening (LSP) parameters on the strengthening effect, the finite element software ANSYS integrated with ISIGHT was adopted to establish a LSP parameterized file. Multi-island genetic algorithm (MIGA) was applied to optimize the process parameters of LSP, and an optimal parameter combination was obtained. The effects of different LSP parameters on the residual stress field and plastic deformation of the treated surface were discussed. Good consistency can be found between the simulation and experimental results under the optimal process parameters, which indicated that the optimization approach was feasible, and some guidance for the future research was also pointed out..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 103003 (2011)
Research on Surface Profile of Copper Treated by Multi-Micro Laser Shock Peening
Fan Yujie, Zhou Jianzhong, Huang Shu, Zhu Wei, Xu Zengchuang, Fan Jinrong, and Gao Bin
In order to investigate the effect of multi-micro laser shock peening on surface morphology, experiments are adopted to analyze the surface profile of copper under different processing conditions. Based on the experimental and theoretical analysis, a reasonable characteristic method is presented, and influence rule of In order to investigate the effect of multi-micro laser shock peening on surface morphology, experiments are adopted to analyze the surface profile of copper under different processing conditions. Based on the experimental and theoretical analysis, a reasonable characteristic method is presented, and influence rule of main processing parameters is also explored. The results show that surface roughness increases after laser shock peening, laser pulse energy and overlapping rate are the main influence factors on surface profile and bearing length ratio. With reasonable characterization of surface morphology, good guidance for further control of surface profile and optimal parameters of microscale laser shock peening are provided..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 103004 (2011)
Study on the Numerical Simulation and Statistical Optimization of Micro-Scale Laser Shock Peening
Zhu Wei, Zhou Jianzhong, Huang Shu, Fan Yujie, Gao Bin, Fan Jinrong, and Xu Zengchuang
In order to ensure high quality of micro scale laser shock peening (μLSP), an appropriate analysis model is established for the numerical simulation of the process, and then some key technical issues in the simulation are studied and solved. By extracting the characteristics of residual stress field and comparing the cIn order to ensure high quality of micro scale laser shock peening (μLSP), an appropriate analysis model is established for the numerical simulation of the process, and then some key technical issues in the simulation are studied and solved. By extracting the characteristics of residual stress field and comparing the calculated data with the process parameters, the critical parameters affecting the value of the characteristics of residual stress field induced by μLSP are searched out. The Box-Behnken optimization program based on the response surface methodology (RSM) is developed to search out the influence of the identified critical parameters and the interaction of the parameters to characteristics of the residual stress field. A quadratic regression model for predicting the average surface residual stress which is one of the characteristics of residual stress field is established, the optimal setting for each process parameter is predicted also..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 103005 (2011)
Effects of Different Laser Shot Peened Coverage Areas on Fatigue Crack Growth of 6061-T6 Aluminum Alloy
Xu Zengchuang, Huang Shu, Zhou Jianzhong, Zuo Lidang, Yang Jing, and Ruan Hongyan
In order to investigate the effect of two-sided laser shot peening (LSP) on fatigue crack growth of 6061-T6 Aluminum alloy compact tension (CT) specimens under different coverage areas, finite element software Abaqus and MSC.Fatigue are used to establish the prediction model. Three different LSP coverage areas, i.e. 15In order to investigate the effect of two-sided laser shot peening (LSP) on fatigue crack growth of 6061-T6 Aluminum alloy compact tension (CT) specimens under different coverage areas, finite element software Abaqus and MSC.Fatigue are used to establish the prediction model. Three different LSP coverage areas, i.e. 15 mm×15 mm, 34.5 mm×15 mm and 15 mm×60 mm are selected. The effects of compressive residual stress on the crack closure by different LSP coverage areas are studied, and the fatigue life increment is predicted. The simulation results indicate that the fatigue crack growth rates of laser peened CT specimens is decreased in comparation with the untreated ones. LSP coverage areas significantly affect the fatigue life of CT specimens, moreover, the specimens treated with 15 mm×60 mm LSP coverage area gain the most obvious fatigue life improvement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 103006 (2011)
Laser Physics
Technology Research on Kilowatt Slab Laser with End-Pumping
Li Mi, Hu Hao, Li Jianmin, Li Deming, Zhao Na, Wu Yingcheng, Jiang Jianfeng, Lei Jun, Lü Wenqiang, and Shi Yong
The Nd:YAG slab laser with laser diode array end-pumping experiment has been developed. According to the characteristic of slab medium, the slab laser with image-inverting resonator (IIR) avoids effectively the beam excursion to the slab end and the instability on laser power. It obtains the quasi-continuous laser outpThe Nd:YAG slab laser with laser diode array end-pumping experiment has been developed. According to the characteristic of slab medium, the slab laser with image-inverting resonator (IIR) avoids effectively the beam excursion to the slab end and the instability on laser power. It obtains the quasi-continuous laser output with the average power higher than 1000 W when the pump power is 3330 W, the slope efficiency is 42.2%, the stability of the output power is better than 1.5%. The beam quality of laser is measured and the relevant academic analysis is done..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102001 (2011)
Analysis on Spreading of Vortex Beam while Propagating
Ding Panfeng, Pu Jixiong, and Ren Hongliang
The analytical expression of the electric field is derived on the observation plane for vortex beam after propagation. Based on the derived result, the intensity distribution and the beam size on the observation plane is analyzed. Different from the traditional Gaussian beam, there is no generous definition for vortex The analytical expression of the electric field is derived on the observation plane for vortex beam after propagation. Based on the derived result, the intensity distribution and the beam size on the observation plane is analyzed. Different from the traditional Gaussian beam, there is no generous definition for vortex beam after propagation. The mean-square width and the equivalent-beam width are put forward to investigate the spreading of vortex beam while propagating. It is shown that the spreading of vortex beam depends on the topological charge and propagation length. The beam with bigger topological charge spreads faster. Calculation results reveal that the equivalent beam length is more suitable to describe the beam size of vortex beam after propagation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102002 (2011)
Influence of Turbulence on the Effective Radius of Curvature of Partially Coherent Hermite-Gaussian Array Beams
Shao Xiaoli, and Ji Xiaoling
The analytical expression for the effective radius of curvature R of partially coherent Hermite-Gaussian (H-G) array beams propagating through atmospheric turbulence is derived, which is general and can be reduced to several typical cases. It is shown that turbulence results in a decrease of R. For the superposition ofThe analytical expression for the effective radius of curvature R of partially coherent Hermite-Gaussian (H-G) array beams propagating through atmospheric turbulence is derived, which is general and can be reduced to several typical cases. It is shown that turbulence results in a decrease of R. For the superposition of the intensity R is less sensitive to turbulence than that for the superposition of the cross-spectral density function. In free space, R of Gaussian Schell-model array beams and Gaussian array beams is larger than that of partially coherent H-G array beams, but it is more affected by turbulence. In free space, R of a single partially coherent H-G beam is smaller than that of the partially coherent H-G array beam, but it is less affected by turbulence. For the superposition of the intensity, the R of fully coherent H-G array beams is larger than that of partially coherent H-G array beams, but it is more affected by turbulence. In general, R is more sensitive to turbulence, if R is larger in free space. Therefore, the R of laser beams with larger R in free space will become smaller than the R of those with smaller R in free space after a certain propagation distance in turbulence..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102003 (2011)
Effect of the Amplitude Modulated Defects on the Intensity Distribution and the Angular Spectrum of a Gaussian beam
Su Qianqian, Zhang Guowen, Tao Hua, and Pu Jixiong
The unavoidable defects existing in optical components will influence the beam propagation in the optical system. Based on the Fresnel diffraction integral and the definition of angular spectrum, the analytical expressions for the light-intensity distribution and angular spectrum of a Gaussian beam modulated by finite-The unavoidable defects existing in optical components will influence the beam propagation in the optical system. Based on the Fresnel diffraction integral and the definition of angular spectrum, the analytical expressions for the light-intensity distribution and angular spectrum of a Gaussian beam modulated by finite-amplitude modulated defects are derived. The influence of the size and the modulation amplitude of the defects on the intensity distribution and angular spectrum of the beam is also studied. It is shown that the intensity distribution will recover to Gaussian distribution after propagating a certain distance. The larger size of defects is, the longer propagation distance is for the beam recovering to Gaussian distribution. Furthermore, the angular spectrum of the modulated beam in the low-frequency area becomes smaller and the angular spectrum in the high frequency area becomes greater with the increase of the size and the modulation amplitude of the defects..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102004 (2011)
Modeling of Longitudinally Nonuniform Thermal Lensing in Diode End-Pumped Solid-State Lasers
Li Bingbin, Guo Zhen, Wang Shiyu, Cai Defang, and Wen Jianguo
A method for modeling the longitudinally non-uniform thermal lensing is proposed, the laser rod is divided into N equivalent segments longitudinally for calculations, each can be dealt as lens-like medium, so both the forward and backward transmission matrix of longitudinally non-uniform thermal lensing can be worked oA method for modeling the longitudinally non-uniform thermal lensing is proposed, the laser rod is divided into N equivalent segments longitudinally for calculations, each can be dealt as lens-like medium, so both the forward and backward transmission matrix of longitudinally non-uniform thermal lensing can be worked out. A quantitative analysis of the fundamental-mode distribution in a plane-parallel cavity is made using transmission matrix. The effect of the dividing number N on waist radius of cavity mode is analyzed, results show waist radius changes with the number N, when N is larger than a certain value, waist radius will tend to stabilization and can get closest to realities. The smallest values of N for the waist radius getting to stabilization are discussed with the variations of the pump power, average pump radius and rare earth ion doping concentration, individually..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102005 (2011)
Trapping Two Types of Particles Using a Partially Coherent Radially Polarized Doughnut Beam
Tian Bo, and Pu Jixiong
The radiation force of focused partially coherent radially polarized doughnut beam acting on a particle (r<λ) in the Rayleigh scattering regime is theoretically studied. Based on the Collins formula, expressions of intensity distribution in the focal region are derived, and the interaction forces between light and tThe radiation force of focused partially coherent radially polarized doughnut beam acting on a particle (r<λ) in the Rayleigh scattering regime is theoretically studied. Based on the Collins formula, expressions of intensity distribution in the focal region are derived, and the interaction forces between light and the Rayleigh particle are calculated using the Rayleigh scattering theory. Numerical calculations are shown to compare the different radiation forces of a partially coherent radially polarized doughnut beam and a partially coherent linear polarized beam. It is found that the radiation forces in the focal field are obviously different with the different correlation widths, and the particles whose refractive index is lower or higher than the ambient can simultaneously be trapped by use of focused partially coherent radially polarized doughnut beams..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102006 (2011)
Vectorial Field Propagation of Semiconductor Laser Beam
Xu Qiang, Liu Yang, and Zhang Wei
For the beam of a laser diode, the source size is very small and the light beam has a large divergence angle. In addition, in the nonparaxial region the optical field distribution is considerably different from that given by scalar theory. The nonparaxial theory of vector beams should be used to describe these fields. For the beam of a laser diode, the source size is very small and the light beam has a large divergence angle. In addition, in the nonparaxial region the optical field distribution is considerably different from that given by scalar theory. The nonparaxial theory of vector beams should be used to describe these fields. A mathematical model to describe the far-field distribution of the nonparaxial laser diode beam is presented. The laser diode beam propagation is studied by the vector Rayleigh diffraction integrals, and the stationary-phase method is employed to find the asymptotic expansion of the diffraction integral. The propagation expression for nonparaxial laser diode beam is given. The calculated results show the vectorial theory model is more precise in the nonparaxial region..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102007 (2011)
Investigation on the Radiation Forces upon a Transparent Plate by a Gaussian Beam
Li Donghua, Pu Jixiong, and Wang Xiqing
A new method is employed to study the radiation forces on a transparent plate illuminated by a Gaussian beam under geometric optics model. Unlike optic traps, it depends only on the deference of light pressure to produce the optical lift. According to the law of conservation of momentum, the formula is derived on the bA new method is employed to study the radiation forces on a transparent plate illuminated by a Gaussian beam under geometric optics model. Unlike optic traps, it depends only on the deference of light pressure to produce the optical lift. According to the law of conservation of momentum, the formula is derived on the basis of angular spectrum theory. The influences of waist radius, transparent plate location and inclination angle are investigated and the distributions of forces are illustrated in longitudinal and transverse components. From the graphical comparison, it is shown that the radiation forces become larger with the waist radius, the distance between transparent plate and the waist radius decreasing. The longitudinal force arrive at the maximum value when the inclination angle is 60°, and the direction always keeps along the z axis. While the transverse forcees along both the positive and negative directions go up to the peak at 70°. The numerical results show that if we choose the appropriate parameters there will be enough transverse forces to conquer the gravity force to move the plate upwards..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102008 (2011)
Study on Polarization Properties of Whispering Gallery Mode Fiber Laser
Feng Li, Zhang Yuanxian, and Pu Xiaoyun
The polarization properties of whispering gallery mode (WGM) fiber laser pumped by evanescent waves are studied. Both transverse electric (TE) wave and transverse magnetic (TM) wave exist on condition that pump beams transmit in a bared optical fiber in skew way, additionally for the same number of radial mode order anThe polarization properties of whispering gallery mode (WGM) fiber laser pumped by evanescent waves are studied. Both transverse electric (TE) wave and transverse magnetic (TM) wave exist on condition that pump beams transmit in a bared optical fiber in skew way, additionally for the same number of radial mode order and angular mode number, the wavelength difference between TE and TM waves monotonely increases with fiber diameter decreasing, and monotonely decreases with the refractive index of cladding solution increasing. The observed experimental results, on the basis of excitation mechanics of evanescent wave pumped WGM fiber laser in combination with the analytic asymptotic formula, validate the theoretical value very well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102009 (2011)
Measurement of Orbital Angular Momentum of an Optical Vortex Beam by Using a Rhombus Aperture
Liu Yongxin, Tao Hua, and Pu Jixiong
The far-field diffraction pattern of a vortex beam by a rhombus aperture is investigated theoretically and experimentally. It is found that the number of the dark stripes in the Fraunhofer diffraction intensity distribution is just equal to the topological charge value of the measured optical vortex, and the centre of The far-field diffraction pattern of a vortex beam by a rhombus aperture is investigated theoretically and experimentally. It is found that the number of the dark stripes in the Fraunhofer diffraction intensity distribution is just equal to the topological charge value of the measured optical vortex, and the centre of each dark stripe is just a phase singularity point. Based on this property, it provides us a simple way to detect the orbital angular momentum (OAM) of an optical vortex beam..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 102010 (2011)
Materials and Thin Films
Theoretical Simulation of Surface Temperature and Stress Distribution of Fused Silica under DF Laser Irradiation
Jiang Tian, and Cheng Xiang′ai
Based on the extensive research of thermoelasticity, the temperature and thermal stress-field distribution curves of the fused silica are studied under irradiation of DF laser. It can be shown that the temperature field distribution and thermal stress field distribution of the fused silica irradiated by DF laser dependBased on the extensive research of thermoelasticity, the temperature and thermal stress-field distribution curves of the fused silica are studied under irradiation of DF laser. It can be shown that the temperature field distribution and thermal stress field distribution of the fused silica irradiated by DF laser depend on the field distribution, power density and irradiation time of lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106001 (2011)
Influence on Different Kinds of Molten Salt on Synthesis and Optical Properties of the Potassium Niobium Impact Research
Cao Huiqun, Zhang Xinpeng, Cao Bo, Yu Bin, Lin Ping, Lin Xin, Zhang Anxiang, Luo Zhongkuan, and Zhang Tao
Potassium niobate crystals have been synthesized by a molten salt process with KCl, K2SO4, K2CO3 or KNO3 as molten salt reactive Nb2O5 materials at 900 ℃ for 2 h. The effect of different kinds of molten salt on the structure and morphological profile of the powers were discussed, and the optical properties of the samplPotassium niobate crystals have been synthesized by a molten salt process with KCl, K2SO4, K2CO3 or KNO3 as molten salt reactive Nb2O5 materials at 900 ℃ for 2 h. The effect of different kinds of molten salt on the structure and morphological profile of the powers were discussed, and the optical properties of the samples were studied. X-ray diffraction results showed that the product is KNb3O8 when the KCl and K2SO4 as molten salt, respectively, and the product is K2NbO4 when the K2CO3 and KNO3 as molten salt, respectively. Scanning electron microscopy results showed that bar was formed with the width of 0.2~0.5 μm and the length of several microns. Using K2SO4 as molten salt, the width of rod is 0.2~1 μm and the length is 1~25 μm. Using K2CO3 as molten salt, the product is not rod-like structure, but irregular granular structure. Using KNO3 as molten salt, the width of rod is 0.2~1 μm and the length is 0.5~4 μm. Part of the rod-like structure connected together. Fluorescence spectra showed that KNb3O8 and K3NbO4 crystals have good fluorescence. Fluorescence studies have shown that the samples have very similar fluorescence spectra with K2SO4, KNO3 and K2CO3 as the molten salt. The samples have good fluorescence which were prepared using KCl, K2SO4 and K2CO3 as molten salt..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106002 (2011)
Large-Size Ho∶Tm∶YLF Crystal Grown by the Czochralski Method
Ma Xiaoming, Wang Yongguo, Yao Baoquan, Cui Yanjun, and Mo Xiaogang
The causes of the floating-debris on the surface of HoTmYLF melt, the scattering particles and the crack of HoTmYLF crystal during the Czochralski growth are analyzed in this paper. Through elaborately designing of the symmetry temperature field, and adjusting temperature gradient and the crystal growth process parametThe causes of the floating-debris on the surface of HoTmYLF melt, the scattering particles and the crack of HoTmYLF crystal during the Czochralski growth are analyzed in this paper. Through elaborately designing of the symmetry temperature field, and adjusting temperature gradient and the crystal growth process parameters, the scattering particles and the crack of the crystal are eliminated effectively. The growth atmosphere with a certain volume CF4 contributes to decreasing the floating-debris on the melt surface effectively, and the influence of the floating-debris on the normal crystal growth are overcome. By above technique ways, high-quality HoTmYLF crystals with the size of (25~30)mm×(100~120)mm are grown. The laser performance test of HoTmYLF crystal shows that under LD double-end-pumped conditions more than 10 W laser at 2.05 μm is achieved, and the laser slope efficiency reaches 41.2%, optical-to-optical efficiency reaches 36.4%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106003 (2011)
Luminescence and Concentration Quenching of Eu2+ in Chlorine Calcium Borate
Tian Shaohua, Li Panlai, and Sun Mingsheng
The yellow phosphor Ca2BO3ClEu2+ was synthesized by high temperature solid state reaction method, and the results show that the phosphor can be excited by the near-ultraviolet and blue light. Under the 460 nm excitation, the phopshor presents a single broad emission band, in which the peak appeared at 573 nm. MontoriedThe yellow phosphor Ca2BO3ClEu2+ was synthesized by high temperature solid state reaction method, and the results show that the phosphor can be excited by the near-ultraviolet and blue light. Under the 460 nm excitation, the phopshor presents a single broad emission band, in which the peak appeared at 573 nm. Montoried at 573 nm, the excitation spectrum cotained 300～500 nm excitation band, and the excitation peaks located at 413 nm and 475 nm, respectively. The effect of Eu2+ concentration on the crystal structure and emission intensity was studied. And the results show that the all patterns data well agreed with the standard data. However, the emission intensity of the phosphor was influenced by the Eu2+ concentration, and the intensity reaches maximal value at 2% Eu2+. According to the Dexter theory, the concentration quenching mechanism is the d-d interaction..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106004 (2011)
Silver Nanoflower Fabricated by Femtosecond Laser Pulses and Its SERS Effect
He Min, Dai Ye, Yu Guangjun, Wu Guorui, Bian Huadong, Jin Zuanming, and Wang Lihua
A nanoflower structure is fabricated on the silver film by a focused 1 kHz femtosecond laser irradiation. By controlling the laser irradiation parameters such as pulse energy, number of pulses and out-of-focus distance, a series of silver nanostructures with respective characteristics are produced. According to the optA nanoflower structure is fabricated on the silver film by a focused 1 kHz femtosecond laser irradiation. By controlling the laser irradiation parameters such as pulse energy, number of pulses and out-of-focus distance, a series of silver nanostructures with respective characteristics are produced. According to the optics and scanning electron microscope (SEM) observations, the formation process of silver nanoflower should be due to the combination of femtosecond laser ablation and successively solidified flow dynamics in molten material. Besides, a possible interference modulation between the incident light field and the induced surface plasmon wave also can be responsible for the formation of silver nanoflower. In the application, the irradiated silver film showed strong surface enhanced Raman scattering (SERS) effect after soaked in R6G solution..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106005 (2011)
Thermoluminescence and Optically Stimulated Luminescence Properties of YAP:Ce Crystal
Chen Jianyu, Cui Hongwei, Si Jiliang, Liu Tingyu, and Tang Qiang
The thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of high quality 0.8% Ce doped YAlO3 crystal (YAP:Ce) which is grown by Czochralski method are studied. It is found that YAP:Ce has high TL and OSL sensitivity comparing with that of high quality TL material LiFMg,Cu,P and OSL dosimetry mThe thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of high quality 0.8% Ce doped YAlO3 crystal (YAP:Ce) which is grown by Czochralski method are studied. It is found that YAP:Ce has high TL and OSL sensitivity comparing with that of high quality TL material LiFMg,Cu,P and OSL dosimetry material Al2O3C. The main glow peak of YAP:Ce locates at 701 K, which is 216 K higher than that of Al2O3C (485 K) and 194 K higher than LiFMg,Cu,P (507 K). The fact means that electrons in the traps of YAP:Ce are stable and are not influenced by the circumstance easily, and can be used in high temperature environment. So YAP:Ce crystal is a promising dosimetry material which can be used in special conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106006 (2011)
Light Absorption Properties of Microstructured Silicon
Chen Changshui, He Huili, Wang Fang, Guo Banghong, and Liu Songhao
Black silicon with quasi-regular arrays of micrometer-sized spikes, which is obtained by irradiating the surface of a Si wafer with ultrafast laser pulses in the presence of a chalcogen-bearing gas, or prepared by ion implantation and pulsed-laser-melting-induced rapid solidification. This new material has unusual optiBlack silicon with quasi-regular arrays of micrometer-sized spikes, which is obtained by irradiating the surface of a Si wafer with ultrafast laser pulses in the presence of a chalcogen-bearing gas, or prepared by ion implantation and pulsed-laser-melting-induced rapid solidification. This new material has unusual optical and electrical properties, such as strong absorption of light with wavelength between 0.25 μm and 17 μm, nice field emission characteristics and so on, offers silicon many new features. Taking chalcogen as example, the enhancement of light absorption of the microstructured silicon is analyzed under four-level model. A detailed study on the relationship between the light loss and the ionization energy of doped impurities in silicon with two different impurity bands..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 106007 (2011)
Influence of the Interface-Continuity on the Damaging Characteristics of Nodular Defects
He Wenyan, Cheng Xinbin, Ma Bin, Ding Tao, Ye Xiaowen, Zhang Jinlong, Zhang Yanyun, Jiao Hongfeng, and Wang Zhanshan
The influence of interface-continuity of nodules that initiate from 2 μm SiO2 particles on the damaging behaviors of HfO2/SiO2 high reflective coatings is discussed. Two kinds of films with different thickness are manufactured using ion-assistant deposition (IAD) technique. These films have similar distribution of elecThe influence of interface-continuity of nodules that initiate from 2 μm SiO2 particles on the damaging behaviors of HfO2/SiO2 high reflective coatings is discussed. Two kinds of films with different thickness are manufactured using ion-assistant deposition (IAD) technique. These films have similar distribution of electronic field and absorption; however, the film with larger thickness (double times) has better interface-continuity. The two kinds of films with engineered defects are irradiated by the 1064 nm(10 ns) laser pulse in the way of raster scan. It is found that the nodules in thicker films had higher initial damage threshold and the damage process is relatively slower. It is shown that for the SiO2 particle with diameter of 2 μm, the continuity of the interface between the nodular defects and surrounding layers become better with the increasing film’s thickness, and its resistance to the laser-irradiation also increased..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 107002 (2011)
Influences of Deposition Pressure on Structures and Optical Properties of Sputtered Aluminum Nitride Films
Huang Meidong, Du Shan, Wang Lige, and Zhang Linlin
Aluminum nitride (AlN) films are fabricated on well polished K9 glass substrate by reactive radio frequency (RF) magnetron sputtering technique. Influence of deposition pressure on microstructure and properties of AlN films is investigated, as other deposition parameters are kept as constants. Experiments as well as siAluminum nitride (AlN) films are fabricated on well polished K9 glass substrate by reactive radio frequency (RF) magnetron sputtering technique. Influence of deposition pressure on microstructure and properties of AlN films is investigated, as other deposition parameters are kept as constants. Experiments as well as simulation are carried out to investigate microstructures and optical properties of the films in terms of deposition pressure. The results indicate that the AlN films are crystalline and the deposition pressure influences orientation of the crystallites. The films are transparent according to the transmittance spectra. The refractive index, obtained by simulation of the transmittance spectra using envelope method, and the deposition rate of the films decreases with increasing deposition pressure. The mechanism of effects of deposition pressure on structure and optical properties of AlN films is tentatively analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 107003 (2011)
Research and Design of a Fiber-Optic Temperature Sensing Film Probe
Hu Jiahui, Tao Chunxian, Zhang Dawei, Huang Yuanshen, and Ni Zhengji
In order to solve nonlinear and unstable problem in measurement, a fiber-optic temperature sensing film probe was designed. The material of the sensing film probe is germanium. The sensing probe is a double-layered film structure, in which the low refractive index material is silicon dioxide and the high refractive indIn order to solve nonlinear and unstable problem in measurement, a fiber-optic temperature sensing film probe was designed. The material of the sensing film probe is germanium. The sensing probe is a double-layered film structure, in which the low refractive index material is silicon dioxide and the high refractive index material is germanium. The detection principle is based on the changes of refractive index of germanium because of the temperature change, resulting in changes in the reflectivity. Practically, we can get the temperature figures by measuring the reflected power. The line linearization of the sensor, which was obtained over a temperature measurement range of 30 ℃~130 ℃ is 99.85%. The results show that the conclusion can meet the purpose of linearization of fiber temperature sensor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 107004 (2011)
Preparation of Composite Anti-Reflective and Protective Films with Diamond-Like Carbon Films on Sulfide Zinc Substrate
Guo Yanlong, Lu Yimin, Huang Guojun, Wang Shuyun, Cheng Yong, Wang Huisheng, and Wan Qiang
Common anti-reflective films on ZnS substrate has low hardness and poor protective effect, so these films cannot function in harsh environment. Diamond-like carbon (DLC) films with high infrared transmittance and high hardness is deposited by quasi-molecule laser in vacuum. Composite anti-reflective and protective filmCommon anti-reflective films on ZnS substrate has low hardness and poor protective effect, so these films cannot function in harsh environment. Diamond-like carbon (DLC) films with high infrared transmittance and high hardness is deposited by quasi-molecule laser in vacuum. Composite anti-reflective and protective films with several common materials including DLC films is developed. The deposition parameters and performance of pure DLC films is optimized. A compound graphite target is made by fix a sector of Ge slice onto a round graphite slice. Unhydrogened Ge doped DLC film is deposited by means of quasi-molecule laser ablation of compound graphite target in vacuum. Compare to pure DLC film, Ge doped DLC film on Si or Ge substrate has higher absorbance in infrared (IR) region, lower transmittance and higher SP3 content. Thus pure DLC films is choosen for the composite films. The adhesion performance of the composite films is improved by introducing adhesive coating, optimizing of the thickness of DLC films and so on. The composite films has many advantages such as high tranmittance in far IR region, good adhesion, anti-scratch and so on, it also pass the boiling water test, tape adhesion test and scrub test..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 107005 (2011)
Measurement and Metrology
Time-Domain Fluorescence Lifetime Measurement and Analysis Using a Streak Camera
Wang Yan, Li Heng, Qi Jing, Shao Yonghong, Qu Junle, and Niu Hanben
A method which describes the impulse response function of the fluorescence lifetime measurement system that based on a streak camera using Gaussian function is presented, and a mathematical model which is used to fit the fluorescence decay curves in time-domain is established. The data of the impulse response function A method which describes the impulse response function of the fluorescence lifetime measurement system that based on a streak camera using Gaussian function is presented, and a mathematical model which is used to fit the fluorescence decay curves in time-domain is established. The data of the impulse response function of the time-domain fluorescence lifetime measurement system built using the Gaussian function are fit. The goodness of the fitting is greater than 0.995. The fluorescence lifetime of the standard fluorescent dye Rose Bengal is measured and the data using the mathematical model are fit. The average goodness of fitting is greater than 0.996 and the standard deviation of lifetime is only 1.7 ps. Experimental results show that the mathematical model is reliable and accurate in processing the time-domain signal obtained by fluorescence lifetime measurement system that is based on a streak camera. The method presented simplifies the deconvolution calculation, improves the precision of lifetime measurement and can be used to process time-domain signals obtained by other systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108001 (2011)
Systematical Errors Correction of the Simultaneous Phase Shifting Interferometry
Li Bo, Chen Lei, Li Jinpeng, and Li Yan
Contrast to the traditional temporal phase shifting interferometry (TPSI), the simultaneous phase shifting interferometry (SPSI) immunes to the time variant error sources such as the vibration but suffers from some new systematical errors caused by the light splitter and polarization phase shifting structures adopted iContrast to the traditional temporal phase shifting interferometry (TPSI), the simultaneous phase shifting interferometry (SPSI) immunes to the time variant error sources such as the vibration but suffers from some new systematical errors caused by the light splitter and polarization phase shifting structures adopted in most SPSI systems. A method is proposed to correct the systematical error in the SPSI, which tests a spherical surface in the SPSI system and obtains the circular carrier interferograms by defocusing, then the power and phase information of each phase shifting interferogram can be calculated using the demodulation method of circular carrier. Guided by these information the systematical errors containing the light splitter, the inaccurate phase shift and the mismatch of interferograms can be corrected respectively. This method is validated by the numerical simulations and experiments, which is suitable for all the SPSI system with light splitter structure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108002 (2011)
A Method of Fixing on Best Position of Reference Spherical Wave Source to Test Aspheric Surface
Mo Weidong, Fan Qi, Jia Jinchao, Zhang Haifang, Feng Mingde, Yang Baiyu, and Li Junsheng
By calculating the interference fringe density of the tested aspheric surface reflected wave and reference spherical wave in the CCD to record interference pattern, the distribution of fringe density is gotten when source of reference spherical wave is in different positions. To compare the maximum fringe density, the By calculating the interference fringe density of the tested aspheric surface reflected wave and reference spherical wave in the CCD to record interference pattern, the distribution of fringe density is gotten when source of reference spherical wave is in different positions. To compare the maximum fringe density, the position of source of reference spherical wave while the maximum fringe density is the smallest in CCD is the position of best-fit spherical surface. The spherical wave emitted in above position is the best reference spherical wave. At the same time, the maximum fringe density is also the important basis for choosing CCD in system of testing aspheric surface by digital holography, which is an important technology parameter to evaluating accuracy of a testing system for aspheric surface. The method can be used to fix on best position of reference spherical wave source for inspecting any aspheric surface, which does not require any analytical calculations about aspheric surface function..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108003 (2011)
Application of the Rainbow Schlieren in the Density Quantitative Measurement of the Supersonic Freejet
Jiang Guanlei, Hong Yanji, Ye Jifei, and Wu Wentang
The rainbow schlieren can be widely used in a lot of typical flow field as a non-invaded optical measurement. It can measure the density and density-grads quantitatively. The rainbow schlieren experiment takes the axis-symmetry free jet as a object, using the typical “Z” schlieren system and Xe-lamp, and replaces the eThe rainbow schlieren can be widely used in a lot of typical flow field as a non-invaded optical measurement. It can measure the density and density-grads quantitatively. The rainbow schlieren experiment takes the axis-symmetry free jet as a object, using the typical “Z” schlieren system and Xe-lamp, and replaces the edge with rainbow filter. The facture and calibration of rainbow filter, the quantitative measure theory, and the date processing are studied in detail. While the freejet of this expriment is simulated, and a accordant result is obtained. The technology supports a reference to the quantitative visual study of the flow measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108004 (2011)
Adopting the Ratio of Defect Size Over Depth to Quantitatively Study the Effect of Defect Size on the Measurement of Defect Depth
Zeng Zhi, Tao Ning, Feng Lichun, and Zhang Cunlin
One aluminum sample whose surface was treated with anode oxidation and one fiber reinforced plastics sample were used in this study, one side of both samples were milled six flat-bottom wedges with different depth. Pulsed thermography was used to obtain the temperature decay data series, the temperature-time curves of One aluminum sample whose surface was treated with anode oxidation and one fiber reinforced plastics sample were used in this study, one side of both samples were milled six flat-bottom wedges with different depth. Pulsed thermography was used to obtain the temperature decay data series, the temperature-time curves of different positions in each wedge were extracted to approximately simulate that the same depth defects were affected with different levels of three-dimensional heat diffusion, and the extracted data can also approximately represent the temperature decay of defects with different ratio of defect size over defect depth (RDSD). The theoretical procedures of thickness measurement were analyzed based on one-dimensional heat conduction model, and the corresponding results were analyzed to compare how the defect size influences the defect depth measurement under the same thickness. The results indicate that the characteristic times of different methods approximately linearly increase with RDSD, and its slope is bigger when defect is deeper or thermal diffusivity is smaller..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108005 (2011)
Core Index Measurement and Calculation of the Ultraviolet-Written Optical Channel Waveguides
Ren Yitao, Huang Yin, Ding Xinren, Zhao Lu, and Tang Yi
The index variation of channel waveguides based on a mode field distribution is studied. The measured mode field distributions are compared with the theoretical ones by acquiring the experimental field distributions of the fundamental mode. The core refractive index and its variations of ultraviolet (UV)-written channeThe index variation of channel waveguides based on a mode field distribution is studied. The measured mode field distributions are compared with the theoretical ones by acquiring the experimental field distributions of the fundamental mode. The core refractive index and its variations of ultraviolet (UV)-written channel waveguides are calculated. Waveguide channels are formed after the UV irradiation of planar waveguides and 1%～3 % index increase occurs in the waveguide core region containing about 20% germanium in mole fraction..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108006 (2011)
Research of Ceramic Insulator Detection Using Pulsed Thermography
Li Zhengliang, Zeng Zhi, Tao Ning, and Zhang Cunlin
Active pulsed thermography is adopted to test the inner defects of ceramic insulators, two high energy flash lamps were used to instantly heat the front surface of the tested ceramic insulator, whose temperature increases because of absorbing heat, the heat conducts into the ceramic insulator, thus it causes the temperActive pulsed thermography is adopted to test the inner defects of ceramic insulators, two high energy flash lamps were used to instantly heat the front surface of the tested ceramic insulator, whose temperature increases because of absorbing heat, the heat conducts into the ceramic insulator, thus it causes the temperature decrease of the front surface, the computer was used to control the infrared camera to capture and record this temperature decreasing process. Pulsed thermography was successfully used to detect impurities and holes in ceramic insulator based on the research of one-dimensional heat conduction model, the deduction and simulation of the first-order derivative of relative thermal contrast, and the processing and analysis of experimental temperature decreasing curves. The study also analyzed and discussed the sequential difference of the first-order derivative thermographic images. The results indicated that pulsed thermography could be used in the detection of inner defects of ceramic insulators..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108007 (2011)
Measurement of Optical Inhomogeneity with Dual-Wavelength Phase-Shifting Interferometry
Zheng Xiaoyi, Wang Yurong, Wang Qingpu, Li Jie, and Du Yanlong
Traditional measurement of optical inhomogeneity always obtain a globle inhomogeneity including surface parallelism, surface shape and systematic errors. Based on the Lorentz-Lorenz dispersion equation, the relationship between optical inhomogeneity and wavelength is analyzed. The difference of optical inhomogeneity inTraditional measurement of optical inhomogeneity always obtain a globle inhomogeneity including surface parallelism, surface shape and systematic errors. Based on the Lorentz-Lorenz dispersion equation, the relationship between optical inhomogeneity and wavelength is analyzed. The difference of optical inhomogeneity in different wavelengths is much smaller than the required precision of optical components′ inhomogeneity in practical application, according to which and optical material′s dispersion properties, absolute measurement method of optical inhomogeneity with dual-wavelength phase-shifting interferometry is proposed. The measurement principle and the proposed formula are both confirmed in computer simulation and optical experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 108008 (2011)
Optical Communication
Dynamic Performance of Silicon Mach-Zehnder Electro-Optic Modulator with Two Silicon Layers
Song Muping, Xie Hang, and Yang Jichao
Silicon photonics is a novel technique for large-scale optic-electronic integration, with which most kinds of optical devices can be designed. Based on free-carrier plasma dispersion, silicon Mach-Zehnder electro-optic modulator (MZM) can achieve high modulation speed over 10 GHz. Considering the need for modulation spSilicon photonics is a novel technique for large-scale optic-electronic integration, with which most kinds of optical devices can be designed. Based on free-carrier plasma dispersion, silicon Mach-Zehnder electro-optic modulator (MZM) can achieve high modulation speed over 10 GHz. Considering the need for modulation speed and power consumption, a kind of silicon MZM based on MOS capacitor electrodes is studied by a simulation method combining electric and optic analytic model. The results show that under the driving voltage of -2 V, when the doping concentration is 1×1015 cm-3, the effective refractive index change of the optical waveguide in silicon MZM is about 1.05×10-5, which results in single modulation arm length of 3.68 cm to realize Vπ and the loss of less than 0.84 dB/cm. When doping concentration is 5×1015 cm-3, the effective refractive index change is only 0.86×10-5, which results in the Vπ length of 4.51 cm and the loss of about 1.36 dB/cm. And varied capacitor electrode structures of silicon MZM may make the visible difference of the modulation performance, including the rise and fall time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105001 (2011)
Research on Techniques and Algorithms of Signal Interrogation in Multi-Channel Fiber Bragg Sensing System
Bi Jie, Wang Yongjun, Zhang Qi, Liu Yongchao, Xin Xiangjun, and Wang Zhi
To improve the capability and detection precision of the fiber Bragg sensing system, the novel interrogation technique and a fast wavelength detection algorithm are proposed for the multi-channel fiber Bragg grating (FBG) sensing system. With the combination of the numerical simulation and experiment, it is demonstrateTo improve the capability and detection precision of the fiber Bragg sensing system, the novel interrogation technique and a fast wavelength detection algorithm are proposed for the multi-channel fiber Bragg grating (FBG) sensing system. With the combination of the numerical simulation and experiment, it is demonstrated that the average precision of interrogation is 2 pm and the resolution is 0.1 pm over the working range of 1525～1585 nm. The system can realize the real-time monitoring of 32 channels more than 1000 sensors. Present work shows that the algorithm described in this paper can reduce the signal noise ratio (SNR) at the input of the system which influences the precision of interrogation. Compared with traditional wavelength detection algorithms, this interrogation method is greatly improved in measurement precision, wavelength range and working reliability. It can well be applied to practical engineering applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105002 (2011)
Optical NRZ-to-RZ Modulation Format Conversion Based on Nonlinear Effects in Silicon Optical Waveguide
Zhang Bolin, and Song Muping
A format conversion from a non-return-to-zero (NRZ) signal to return-to-zero (RZ) signal is presented based on four-wave mixing (FWM) and cross-phase modulation (XPM) in a silicon optical waveguide. When a NRZ signal acting as the probe and a periodic pulse train as the pump are launched into the silicon waveguide syncA format conversion from a non-return-to-zero (NRZ) signal to return-to-zero (RZ) signal is presented based on four-wave mixing (FWM) and cross-phase modulation (XPM) in a silicon optical waveguide. When a NRZ signal acting as the probe and a periodic pulse train as the pump are launched into the silicon waveguide synchronously, the Stokes and anti-Stokes are generated by FWM and the red and blue shifts are induced by XPM in the probe spectrum. Four RZ signals can be then extracted by utilizing appropriate optical bandpass filters (OBPF). The power variations in the Stokes and anti-Stokes due to the change of pump and probe power, the relation between four RZ signal pulse widths and pump pulse width, and the influence of the wavelength detuning of pump to probe on the conversion efficiency etc. are investigated. Furthermore, the pump pulse width affects the qualities of XPM-induced RZ signals. When the pump pulse width ranges from 2 to 15 ps, four high-quality RZ signals can be obtained. And when the pulse width is larger than 15 ps, the RZ signal filtered from blue shift spectrum of the probe is of bad quality..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105003 (2011)
Application of the Wire Metal Grating in the Fiber Sensors
Zhang Ming, Zhao Yun, Zhou Feng, Xu Fei, and Lu Yanqing
The wire metal grating (WMG) is fabricated on the tip of a standard single mode fiber (SMF) at 1550 nm wavelength by focused ion beam (FIB) technology. The metal used is Au and period of the grating is 200 nm, much smaller than the wavelength of incident light. The transmission light entering the structure is polarizatThe wire metal grating (WMG) is fabricated on the tip of a standard single mode fiber (SMF) at 1550 nm wavelength by focused ion beam (FIB) technology. The metal used is Au and period of the grating is 200 nm, much smaller than the wavelength of incident light. The transmission light entering the structure is polarization according to the effective medium theory (EMT)）.The reflection contrast between TE and TM modes in our experiment reaches 13.7 dB, which is sensitive enough to monitor the polarization change induced by photoelastic effect and Faraday effect. Based on this WMG grating, a pressure sensor with the sensitivity of 0.237 rad/N and a current sensor with the sensitivity of 0.06022°/A are presented..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105004 (2011)
Ultracompact 2×2 Power Splitter Based on Asymmetric Multimode Interference Effect in Photonic Crystal Slab with an Air Holes Array
Zhang Jun, Yu Tianbao, Hu Airong, and Wang Tongbiao
The properties of two-fold images based on asymmetric interference in PC slab multimode waveguide with an air holes array are investigated. With these image properties, a new kind of 2×2 ultracompact power splitters (PSs) is designed and studied. Arbitrary splitting ratio can be achieved by modifying the effectiveThe properties of two-fold images based on asymmetric interference in PC slab multimode waveguide with an air holes array are investigated. With these image properties, a new kind of 2×2 ultracompact power splitters (PSs) is designed and studied. Arbitrary splitting ratio can be achieved by modifying the effective refractive indices of one pair of air holes in the multimode region. As an example, a 3 dB ultracompact 2×2 power splitter with a size of 16 μm×8 μm, with output efficiency as high as 97% is presented with finite-difference time-domain simulations. The method can be extended for the design of M×N PSs and have potential application for photonic integrated circuits applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105006 (2011)
Multi-User 10 Gb/s Optical Code Division Multiple Access Experiment
Zheng Jilin, Wang Rong, Pu Tao, Lu Lin, Fang Tao, Su Yang, Zhu Lei, Xiang Peng, Wei Zhihu, and Chen Xiangfei
To recover the decoded signals based on the existing commercial receiver modules is an important practical developing direction of optical code division multiple access (OCDMA) systems. The en/decoders with high power-contrast-ratio (PCR) can help to form the electrical decision signals with high signal-noise-ratio (SNTo recover the decoded signals based on the existing commercial receiver modules is an important practical developing direction of optical code division multiple access (OCDMA) systems. The en/decoders with high power-contrast-ratio (PCR) can help to form the electrical decision signals with high signal-noise-ratio (SNR) under the narrow-band receiver condition. Based on the commercial narrow-band receiver, i.e., 10 G PIN+TIA and 10 G clock data recorery (CDR), two-user 10 Gb/s 60 km error-free transmission experiment is implemented with the self-designed fiber-Bragg-grating (FBG)-based en/decoders with high PCR. The three-user 10 Gb/s back-to-back (BTB) error-free experiment is also achieved. In the experiment, different bit-error-rate (BER) curves are tested with different users and w/o transmission. Both the impairing factors which cause the power punishment and the approaches to improve sytem performance are analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105007 (2011)
Optical Properties of Side-Polished Fiber with Two-Dimensional Photonic Crystal Lattice
Wang Min, Dai Jixiang, and Yang Minghong
An optical model of side-polished photonic crystal fiber (SP-PCF) is presented firstly, then simulations and experiments are carried out to investigate the optical characteristics of the SP-PCF under different conditions, i.e., different side-polished depths and different covered materials. The results of both the simuAn optical model of side-polished photonic crystal fiber (SP-PCF) is presented firstly, then simulations and experiments are carried out to investigate the optical characteristics of the SP-PCF under different conditions, i.e., different side-polished depths and different covered materials. The results of both the simulations and the experiments show that there exists a side-polished sensitive area. When the polished depth is changing in the area, the refractive index of the covered material has obvious influence on the the effective refractive index of fundamental mode of the SP-PCF. According to the results, SP-PCF could be used as ambient refractive index sensor, and it has potential applications as miniature bioorchemical sensors..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105008 (2011)
Remote Sensing and Sensor
Denoising Method for Ladar Range Images Based on Non-Local Means
Li Qi, Xia Zhiwei, Ding Shenghui, and Wang Qi
A denoising method for coherent ladar range images is proposed based on non-local means (NLM) filtering. Combined with image fusion methods for images such as range image and filtered intensity image, median filter and NLM with background suppression (B-S), B-S and range anomalies can be realized. Image denoising are cA denoising method for coherent ladar range images is proposed based on non-local means (NLM) filtering. Combined with image fusion methods for images such as range image and filtered intensity image, median filter and NLM with background suppression (B-S), B-S and range anomalies can be realized. Image denoising are carried out on simulated coherent ladar multi-target images with different carrier to noise ratios, and the performances are compared with some other methods such as Lee filter. The results show that, the proposed method can satisfy the requirements from the aspects of background noise suppression, normal range values on the target and edge-preservation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114001 (2011)
Effects of Kind and Size of Filter Function on Phase Retrieval for the Wavefront Sensor Based on Pupil Phase Diversity
Yang Huizhen, Gong Chenglong, and Li Yaoqiu
An appropriate filter function is the key to successful wavefront retrieval for the wavefront sensor based on pupil phase diversity. The effects of kind and size of filter function on phase retrieval are investigated through several kinds of filter functions and different sizes of filter functions based on the mode of An appropriate filter function is the key to successful wavefront retrieval for the wavefront sensor based on pupil phase diversity. The effects of kind and size of filter function on phase retrieval are investigated through several kinds of filter functions and different sizes of filter functions based on the mode of wavefront sensor and Zernike decomposition. Simulation results show that the kind of filter function has almost no effect on retrieval effect as long as the size of filter function is within an appropriate range, such as peak vale (PV) is between π rad and 3π rad for the defocus and PV is less than or equal to π rad for the sphere. The restoring accuracy is gradually decreasing as increasing of filter function size, such as PV is bigger than 3π rad for the defocus and π rad for the sphere. In real application, the kind of filter function can be chosen based on the cost and complex of making filter function while the size of filter function is within an appropriate range..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114002 (2011)
Localization Algorithm by the Detection of Single Satellite Infrared Detector with the Support of Missile Navigation Information
Wang Liguang, Jing Zhanrong, and Wang Lingling
It is a disadvantage for ballistic missile to escape interceptor having no detector to get information of interceptor. To resolve this problem, the algorithm to locate interceptor by the detection of space tracking and surveillance system (STSS) single infrared detector with the support of missile navigation informatioIt is a disadvantage for ballistic missile to escape interceptor having no detector to get information of interceptor. To resolve this problem, the algorithm to locate interceptor by the detection of space tracking and surveillance system (STSS) single infrared detector with the support of missile navigation information is proposed. If interceptor is captured by IR detector, it must locate in the line of sight from detector to interceptor. During the head-on interception, exoatmospheric kill vehicle (EKV) locates in the ballistic plane of penetration missile. The intersection point of detector measurement sight line and penetration missile′s ballistic plane is the position of interceptor. The feasibility that STSS infrared sensor can detect the EKV is demonstrated. Then the algorithm implement approach is expatiated and the numeral simulation of the localization algorithm is carried out. Finally, the localization error and its reasons are analyzed. It is indicated that the algorithm can provide a method for missile to locate the position of interceptor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114003 (2011)
Spectral Surface Plasmon Resonance Sensor Insensitive to the Thickness of Metal Films
Liu Le, Liu Zhiyi, Chen Xiangliang, Ma Suihua, Du Chan, He Yonghong, and Guo Jihua
Surface plasmon resonance (SPR) sensing technique has a very high refractive-index (RI) resolution. However, this RI resolution is very sensitive to the thickness of metal films, deteriorating the adaptability of SPR sensors. The sensitivity of RI resolution of a spectral SPR sensor to the thickness of metal films is rSurface plasmon resonance (SPR) sensing technique has a very high refractive-index (RI) resolution. However, this RI resolution is very sensitive to the thickness of metal films, deteriorating the adaptability of SPR sensors. The sensitivity of RI resolution of a spectral SPR sensor to the thickness of metal films is reduced by a technique called "polarization interferometry (PI)". That the PI technique could reduce the minimum of the SPR spectrum is experimentally demonstrated, and the RI resolution of the sensors with non-optimal metal films is improved. RI resolution ranging from 3.9×10-7 to 8.1×10-7 refractive index unit (RIU) is achieved with the thickness of the Au film ranging from 28.16 to 54.38 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114004 (2011)
Implementation of Self-Aligning System with a Single Click for the Lidar
Tan Ying, Wu Xiaying, Peng Xinzhong, and Yi Fan
In order to get the right lidar data, a well alignment of transmitter-receiver optical system is essential. To get right lidar data when the laser beam moves slightly, it is necessary to adjust the beam to the center of the telescope field of view. The laser sweeps the space describing a spiral in the plane at the begiIn order to get the right lidar data, a well alignment of transmitter-receiver optical system is essential. To get right lidar data when the laser beam moves slightly, it is necessary to adjust the beam to the center of the telescope field of view. The laser sweeps the space describing a spiral in the plane at the beginning until a small part of the beam is detected by the telescope. Then a cross scanning of beam is presented to adjust the laser beam until it falls in the center of the telescope field of view. A dedicated software has been developed to execute the self-alignment procedure. The self-alignment of transmitter-receiver optical system can be accomplished with a single click..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114005 (2011)
Dual-Channel Polarization Lidar Monitoring of Sandstorm and Its Transportation Research
Fan Guangqiang, Liu Jianguo, Zhang Tianshu, Dong Yunsheng, Zhao Xuesong, Xie Pinhua, and Liu Wenqing
The charactistic, the main parameters and the data processing solution of two-wavelength polarization lidar are introduced. The sand pollution transportration process before and after the opening ceremony for the Shanghai World Expo is studied. The results show that the sandstorm was transported from northwest , by bacThe charactistic, the main parameters and the data processing solution of two-wavelength polarization lidar are introduced. The sand pollution transportration process before and after the opening ceremony for the Shanghai World Expo is studied. The results show that the sandstorm was transported from northwest , by backward trajectories analysis the sandstorm comed from the Inner Mongolia region. The sandstorm ceascced and formend again in the sandstorm transportation. After sandstorm, the main wind direction changed into northeast, which was favorable for removing sand particle. The comparision between extinction coefficient by the polarization lidar measurement and the ground PM10 air pollution index (API) is presented ,which shows the satisfactory coherence of the different method-derived results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114006 (2011)
Simulation of the Space-Borne Laser Altimeter Based on Pseudorandom Code Phase Modulation and Heterodyne Detection
Yang Fu, Zhan Yage, Yang Qinyu, Xue Shaolin, and He Yan
A method base on the techniques of pseudorandom code (PRC) phase modulation of the fiber laser and heterodyne detection to realize a high spatial resolution for the space-borne laser altimeter is proposed. The altimeter′s equation of the signal to noise ratio is deduced. The relations between the signal to noise ratio A method base on the techniques of pseudorandom code (PRC) phase modulation of the fiber laser and heterodyne detection to realize a high spatial resolution for the space-borne laser altimeter is proposed. The altimeter′s equation of the signal to noise ratio is deduced. The relations between the signal to noise ratio and range resolution with the laser transmit power, local oscillator power, telescope aperture, modulation rate and pseudorandom code length are numerically simulated. The relations between the parameters and the optimized parameters are obtained after the system analysis. Results show that the space-borne altimeter can achieve the design objective of the signal to noise ratio of 10, and the distance resolution of 15 cm when the transmit laser power is about 10 W, local oscillator power is about 10 mW, telescope aperture is 0.4 m, modulation rate is 1 GHz, and PRC length is about 300 μs in a single periodic time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 114007 (2011)
Spectroscopy
Spectral Analysis and Pressure Broadening Mechanism of Laser Diode-Pumped Rubidium Vapor Laser D1 and D2 Lines
Yang Jing, Pan Bailiang, Wang Yajuan, Liu Yunfeng, and Li Meihua
Based on an overall consideration of the frequency shifts caused by rubidium isotopes, pressure broadening and hyperfine splitting, a physical model is established to compute the hyperfine splitting structure of rubidium D1, D2 lines. The influence of buffer gas pressure and the cell temperature on the optical cross seBased on an overall consideration of the frequency shifts caused by rubidium isotopes, pressure broadening and hyperfine splitting, a physical model is established to compute the hyperfine splitting structure of rubidium D1, D2 lines. The influence of buffer gas pressure and the cell temperature on the optical cross section of rubidium D1 and D2 lines is analyzed quantitatively, a group of optimized parameters about line shape and bandwidth are obtained. The good agreement between the simulation and the experiment shows the model provides an effective way for understanding the pressure broadening mechanism of alkali atom D1 and D2 lines and matching the bandwidth of D2 absorption line with the diode laser pump source..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 115001 (2011)
Application of Laser Induced Breakdown Spectroscopy in Measurement of Heavy Metal Cr in Soil using Artificial Neural Network
Liu Lituo, Liu Jianguo, Zhao Nanjing, Chen Dong, Shi Huan, Wang Chunlong, Zhang Yujun, and Liu Wenqing
Nd:YAG laser, OceanHR2000+containing ICCD spectrometer are used for the laer induced-breakdown spectroscopy (LIBS) system. LIBS spectral data is acquired after the reasonable experimental parameters are setting. Using back-propagation artificial neural network (BP-ANN) algorithm, the heavy metal samples of Cr in soil wNd:YAG laser, OceanHR2000+containing ICCD spectrometer are used for the laer induced-breakdown spectroscopy (LIBS) system. LIBS spectral data is acquired after the reasonable experimental parameters are setting. Using back-propagation artificial neural network (BP-ANN) algorithm, the heavy metal samples of Cr in soil which contain different concentrations of Cr are analysed. The peak at 425.435 nm of Cr is chosen to be the inputs whose intensity is normalized by the inner reference element of Fe at 425.079 nm. The net is trained and the qualitative analysis model is construted. Using this model sets of data are used for validation. The results of relative standard deviation (RSD) and mean square error (MSE) are both better than the traditional method of calibration curve..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 115002 (2011)
Concentration Monitoring of O3 Based on Fourier Transform Infrared Spectroscopy and Its Variation Analysis
Feng Mingchun, Gao Minguang, Xu Liang, Cheng Siyang, Li Xiangxian, and Liu Wenqing
Ozone O3 of the surface air layer is one of the frontiers in the environmental science research today. It has very important significance to carry out ambient air monitoring and analysis of O3 for prevention and control of atmospheric pollution. O3 is continuously monitored by using multi-reflected White cell Fourier tOzone O3 of the surface air layer is one of the frontiers in the environmental science research today. It has very important significance to carry out ambient air monitoring and analysis of O3 for prevention and control of atmospheric pollution. O3 is continuously monitored by using multi-reflected White cell Fourier transform infrared (FTIR) spectroscopy in Zhejiang province in July and December, 2010. The monthly variations and diurnal variations of O3 are analyzed by the O3 concentration data. The high concentration of O3 in July is related with strong radiation and high temperature. The diurnal variation of O3 concentration is markedly high in the afternoon and is generally low in the morning and evening..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 115003 (2011)
Detection of Hydrogen Chloride Gas Concentration Based on Multi-Reflection Cell FTIR Spectroscopic Method
Cheng Siyang, Gao Minguang, Xu Liang, Liu Jianguo, Liu Wenqing, Wei Xiuli, Feng Mingchun, Tong Jingjing, Jin Ling, Li Sheng, and Li Xiangxian
The hydrogen chloride is harmful to the environment and causes water pollution.It is mostly produced by the incineration of urban living garbage,medical waste and so on. According to the limitations of volumertric method for nitric acid silver,thiocyanate mercury spectrophotometry and ion chromatography to monitor the The hydrogen chloride is harmful to the environment and causes water pollution.It is mostly produced by the incineration of urban living garbage,medical waste and so on. According to the limitations of volumertric method for nitric acid silver,thiocyanate mercury spectrophotometry and ion chromatography to monitor the hydrogen chloride gas, multiple reflecton cell Fourier transform infrared spectrophotomery method is presented to detect the hydrogen chloride gas concentration. Based on accurately measuring the infrared absorption spectrum of the hydrogen chloride gas, spectrum is quantitatively analysised by using nonlinear least square algorithm in order to get the hydrogen chloride gas concentration. With the concentration results under laboratory conditions,this mehod is also effective way to quantitatively analyse the hydrogen chloride gas..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 115004 (2011)
Measurement of Trace Copper in Water Based on Laser-Induced Breakdown Spectroscopy
Wang Chunlong, Liu Jianguo, Zhao Nanjing, Shi Huan, Lu Cuiping, Liu Lituo, Ma Mingjun, Zhang Wei, Chen Dong, Zhang Yujun, and Liu Wenqing
The spectroscopy emission characteristics of trace heavy metal copper in water enriched with graphite is studied based on laser induced breakdown spectroscopy (LIBS) technique, with a 1064 nm wavelength NdYAG laser as excitation source, the echelle spectrometer and intensified charge coupled device detector are used foThe spectroscopy emission characteristics of trace heavy metal copper in water enriched with graphite is studied based on laser induced breakdown spectroscopy (LIBS) technique, with a 1064 nm wavelength NdYAG laser as excitation source, the echelle spectrometer and intensified charge coupled device detector are used for spectral separation and high sensitive detection with high resolution and wide spectral range. The characteristic spectral line of 324.75 nm with detection delay time 1100 ns and gate time 2100 ns is selected for copper (Cu) in the experiment. The calibration curve of Cu is plotted based on different concentration measurement results, and the limit of detection with 0.0672 mg/L is obtained for Cu in water. The reference data is provided for further study on the fast measurement of trace heavy metals in water by laser induced breakdown spectroscopy technique..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 115005 (2011)
Research on Concentration Retrieval with Gas FTIR Spectra by Interval Extreme Learning Machine Method
Chen Yuanyuan, Zhang Jilong, Wang Zhibin, Zhao Donge, and Chen Youhua
To retrieve the gas concentration accurately and rapidly, a new quantitative analysis technique based on Fourier transform infrared spectroscopy of interval extreme learning machine (ELM) model is proposed. Based on the idea of interval division, this approach firstly divides the whole spectrum into several subintervalTo retrieve the gas concentration accurately and rapidly, a new quantitative analysis technique based on Fourier transform infrared spectroscopy of interval extreme learning machine (ELM) model is proposed. Based on the idea of interval division, this approach firstly divides the whole spectrum into several subintervals, secondly establishes quantitative analysis model corresponding to each subinterval with ELM method, and finally selects the best subinterval combinations according to the determination coefficient of each model. Based on the above approach, wavelengths are selected in the spectrum of NO and NO2, and then establishs the quantitative analysis model using the selected spectrum combinations, respectively. The experimental results showed that, the testing set determination coefficient of NO and NO2 are 0.9999 and 0.9997, respectively. The outcome indicates that, compared with Interval partial least squares method, the proposed Interval ELM method can establish quantitative analysis model more rapidly and accurately..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 115006 (2011)
Terahertz Technology
Study on the Measurement Error on Corneal Vergence for Eyes After Corneal Refractive Surgery
Liu Yongji, Wang Yan, Wang Zhaoqi, Zuo Tong, and Kong Qiang
The radius of anterior and posterior corneal surface, central corneal thickness and Q value of anterior and posterior corneal surface are obtained. Based on the corneal data, the effects of equivalent refractive index and error in radius of curvature on the corneal vergence measurement after refractive surgery are studThe radius of anterior and posterior corneal surface, central corneal thickness and Q value of anterior and posterior corneal surface are obtained. Based on the corneal data, the effects of equivalent refractive index and error in radius of curvature on the corneal vergence measurement after refractive surgery are studied theoretically. The measurement error induced by equivalent refractive index and error in radius of curvature increases with the Q value of corneal anterior surface (P<0.05). Both the equivalent refractive index and error in radius of curvature lead to the overestimation of the corneal vergence, and the additive effects of the equivalent refractive index and error in radius of curvature lead to the overestimation of the corneal vergence by the clinical instruments. In addition, the measurement error linearly relates to the Q value of anterior corneal surface (P<0.05). The error in radius of curvature as well as the equivalent refractive index should be considered in the corneal vergence measurement for eyes after refractive surgery..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 104003 (2011)
Study of a Novel SU-8 Fiber Fabry-Perot Pressure Sensor
Dai Lihua, Wang Ming, and Rong Hua
A novel pressure sensor based on a high-aspect-ratio structure formed by SU-8 photoresist is proposed. The advantage of the structure lies mainly in the design of separation of sensing membrane deformation with the length change of Fabry-Perot (F-P) cavity, which restricts the linear measurement in most traditional preA novel pressure sensor based on a high-aspect-ratio structure formed by SU-8 photoresist is proposed. The advantage of the structure lies mainly in the design of separation of sensing membrane deformation with the length change of Fabry-Perot (F-P) cavity, which restricts the linear measurement in most traditional pressure sensors. The sensor is based on F-P interferometer and phase demodulation method. The structural parameters have been ascertained, which will be dealt with during sensor fabrication through numerical simulation. The main sensing elements of the designed model include a silicon membrane and a square column on it. The membrane is with diaphragm thickness of 100 μm and radius of 1500 μm. Meanwhile, the square column is with the dimension of 100 μm×100 μm×400 μm. The sensitivity of the structure model is presented as 2.606 μm/MPa from simulation. Under the guidance of the simulations, the fundamental processing is defined..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 105005 (2011)
Eliminating Surface or Bulk Scattering of Super-Smooth Transparent Substrate
Zhao Yun, and Yang Kaiyong
Through the analysis of electric polarization angle difference between surface and bulk scattering by first-order perturbation angle-resolved scattering theory, the electric polarization angle between surface and bulk scattering is constant when incidence angle and scattering angle are decided. So polarization angle ofThrough the analysis of electric polarization angle difference between surface and bulk scattering by first-order perturbation angle-resolved scattering theory, the electric polarization angle between surface and bulk scattering is constant when incidence angle and scattering angle are decided. So polarization angle of polarizer and analyzer are controlled to eliminate surface scattering or bulk scattering, and the bulk scattering or surface scattering can be detertal independently. A method in theoritical is applied to eliminating surface or bulk scattering of transparent substrate in this paper, when scattering plane in the incident plane and polarizer angle is 45°, through the numerical study, the analyzer angle is gotten in s-p plane. Thus, the surface scattering or bulk scattering is obtained to study surface roughness or bulk inhomogeneous..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 107001 (2011)
Terahertz Filtering Based on Subwavelength Artificial Materials
Liu Jianfeng, Zhou Qingli, Shi Yulei, and Zhang Cunlin
At present, Some devices based on subwavelength metallic structures and working in microwave regime have been designed due to the special optical properties of subwavelength artificial materials. However, in terahertz (THz) regime, because of the small size and the limit of source and detection of THz wave, THz functioAt present, Some devices based on subwavelength metallic structures and working in microwave regime have been designed due to the special optical properties of subwavelength artificial materials. However, in terahertz (THz) regime, because of the small size and the limit of source and detection of THz wave, THz functional devices develop slowly. For developing THz filters, by finite-difference time-domain (FDTD) method, the optical properties of an array of subwavelength metallic bars′ combinations are studied in this article. The results show that several absorption peaks appear in the transmission spectra when a unit cell of the structure contains several bars. So, multi-band filter can be made on the basis of the property. In addition, by changing the structure, wideband filter can be realized in THz regime..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111001 (2011)
Research of Terahertz Wave Detection System Based on Bi-Material Micro-Cantilever Arrays
Su Bo, Duan Guoteng, and Zhang Cunlin
A new detection system for detecting terahertz (THz) wave radiation is described. The niobium nitride and aluminium are used to fabricate the bi-material micro-cantilever arrays. The role of the niobium nitride is to absorb THz wave radiation, and the aluminium is the deformation material. The bi-material of niobium niA new detection system for detecting terahertz (THz) wave radiation is described. The niobium nitride and aluminium are used to fabricate the bi-material micro-cantilever arrays. The role of the niobium nitride is to absorb THz wave radiation, and the aluminium is the deformation material. The bi-material of niobium nitride and aluminium has the characters of a large difference in thermal expansion coefficient and deformation after absorbing heat, so it can combine the technology of bi-material micro-cantilever arrays detecting infrared and realize the detection of THz wave. The micro-electromechanical system (MEMS) technology is adopted to fabricate the substrate-free bi-material micro-cantilever arrays. In order to prevent the heat diffusion, the micro-cantilever is placed in a vacuum chamber which has the function of vibration prevention, and the mechanical pump and molecular pump are used to keep the high vacuum for improving the signal-to-noise ratio of the detection system. The reflection-type visible light optical readout way is used to acquire the THz wave information indirectly. Furthermore, the method of difference processing is used to process image for improving resolution of the system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111002 (2011)
Single-Pixel Terahertz Imaging Based on Compressed Sensing
Zhao Yaqin, Zhang Liangliang, Zhu Dechong, Liu Xiaohua, and Zhang Cunlin
A terahertz (THz) imaging system and the image formation is based on the theory of compressed sensing (CS) is described. CS combines sampling and compression into a single non-adaptive linear measurement process, and then reconstructs the original image by using measurements based on reconstruction algorithm. It is abtA terahertz (THz) imaging system and the image formation is based on the theory of compressed sensing (CS) is described. CS combines sampling and compression into a single non-adaptive linear measurement process, and then reconstructs the original image by using measurements based on reconstruction algorithm. It is abtained that a single intensity value by measuring the inner of a single mask and original image and a series of measurements with the same number of masks. CS permits the reconstruction of a N pixel×N pixel image using much fewer than N2 measurements to reduce the imaging time. This approach eliminates the need for raster scanning of the object or the THz beam, while maintaining the high sensitivity of a single-element detector. The experiment using a backward wave oscillator (BWO) which is a continuous-wave THz source and get a preliminary test result..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111003 (2011)
Terahertz Wave Reference-Free Spectroscopic Analysis
Zhang Liangliang, Zhong Hua, Deng Chao, Zhang Cunlin, and Zhao Yuejin
A reference-free spectroscopic analysis method for terahertz (THz) transmission and reflection measurement is presented. The absorption features of weakly polarized materials (RDX, 2,4-DNT and HMX) are extracted without the reference signal. For transmission spectroscopy, the absorption peaks can be located from the neA reference-free spectroscopic analysis method for terahertz (THz) transmission and reflection measurement is presented. The absorption features of weakly polarized materials (RDX, 2,4-DNT and HMX) are extracted without the reference signal. For transmission spectroscopy, the absorption peaks can be located from the negative first-order derivative of the sample signal phase divided by the frequency. The absorption signatures of the reflection spectroscopy of the materials are extracted directly from the second-order derivative of the phase of the sample beam with respect to frequency. For reflection spectroscopy, the absorption signatures of the materials are extracted directly from the second-order derivative of the phase of the sample beam with respect to frequency. This technique provides a straightforward and fast solution to solve the phase-retrieval problem in reflection fime-domain spectroscopy (RTDS) and eliminates the “misplacement error”..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111004 (2011)
Numerical Simulation of Filtering Characteristics of Two-Dimensional Metallic Grid in Terahertz Band
Liu Liming, Zhao Guozhong, and Wei Bo
Based on finite difference time domain (FDTD) method, the numerical simulation of filtering characteristics of the two dimensional metal grid which include the well-shaped grid, the array of complementary square metallic pill and the cross wire-hole array are carried out. The results show that the well-shaped metal griBased on finite difference time domain (FDTD) method, the numerical simulation of filtering characteristics of the two dimensional metal grid which include the well-shaped grid, the array of complementary square metallic pill and the cross wire-hole array are carried out. The results show that the well-shaped metal grid structure achieves a high-pass of filter function, the array of square metallic pill achieves a low-pass of filter function, and the cross wire-hole array structure achieves a band-pass of filter function. Simulation results show that, with the increasing of the period the cut-off frequency of high-pass filter and low-pass filter move to low-frequency, and the center frequency allowed by the cross wire-hole array similarly moves to the low-frequency. The result of the multi-layer structure of the cross wire-hole array shows that, the rising edge and the falling edge become very steep when the spacing between layers is 20 μm and the more than 5 layers are used which greatly improved the filtering performance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111005 (2011)
Terahertz Focal Plane Array Based on Bi-Material Micro-Cantilever
Duan Guoteng, Su Bo, Zhang Cunlin, and Zhao Weirei
A real-time imaging system for terahertz (THz) radiation is presented. The key component of the system is the focal plane array (FPA). Which is a bi-material micro-electro mechanical systems (MEMS) detector array optimized for infrared wave lengths. In order to get a better THz image, the paper presents a modified FPA A real-time imaging system for terahertz (THz) radiation is presented. The key component of the system is the focal plane array (FPA). Which is a bi-material micro-electro mechanical systems (MEMS) detector array optimized for infrared wave lengths. In order to get a better THz image, the paper presents a modified FPA for THz region. Two main methods are explored to improve the detector performance in the THz region. The first way identified is the use of novel optical readout system based on surface plasma resonator (SPR). The second detector improvement approach involving the change of the micro-cantilever structure that the cantilever of each pixel can shift in vertical direction. A model of one pixel is set up to optimize the structure. Computer simulation results show that both approaches are effective. The manufacturing of the proposed detector are also discussed. The technological investigation shows that it is feasible to employ sacrificial layer technique related to MEMS technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111006 (2011)
Terahertz Transmission Properties through Asymmetrical Cross Metallic Structures by the Numerical Simulation
Wei Bo, Zhao Guozhong, Liu Liming, and Zhang Shengbo
The numerical simulation is applied to analyze Terahertz (THz) transmission properties of the asymmetrical cross periodic metallic structures, which is based on the finite-difference time-domain (FDTD) method. The results show that there exists the band elimination in the THz transmission spectrum for the cross metalliThe numerical simulation is applied to analyze Terahertz (THz) transmission properties of the asymmetrical cross periodic metallic structures, which is based on the finite-difference time-domain (FDTD) method. The results show that there exists the band elimination in the THz transmission spectrum for the cross metallic structures. When we investigate the effect of THz transmission properties caused by the offset and keep the length, width and period of the metallic structures unchanged, the frequency location of the transmission depression moves towards low frequency as increasing the offset of one metallic. By rotating the sample and changing the polarization of THz electric field related to the direction of one metallic, THz transmission of the asymmetrical cross metallic structure is strongly sensitive to the polarization, while the symmetrical cross structure is independent of THz polarization..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111007 (2011)
Terahertz Broadband Spectroscopic Investigations of Amino Acid
Zhu Dechong, Zhang Liangliang, ZhaoYaqin, Zhang Xin, Wang Xiaoyan, and Zhang Cunlin
We present an experimental terahertz (THz) spectroscopic investigation of amino acid using an air-breakdown-coherent detection (ABCD) system. The strong and ultra-broadband (0.1~10 THz) terahertz radiations generated by two-color laser induced air plasma and measured by coherent heterodyne detection. The broadband THz We present an experimental terahertz (THz) spectroscopic investigation of amino acid using an air-breakdown-coherent detection (ABCD) system. The strong and ultra-broadband (0.1~10 THz) terahertz radiations generated by two-color laser induced air plasma and measured by coherent heterodyne detection. The broadband THz reflection spectra of L-lysine (C6H14N2O2) and L-arginine (C6H14N4O2) are obtained. To solve the phase-retrieval problem in reflective THz time-domain spectroscopy (TDS), the absorption signatures of the materials are extracted directly from the first derivative of the relative reflectance with respect to frequency. The absorption features of the two amino acids are characterized in the 0.5~6 THz region. It is found that both the two amino acids have an absorption peak at 1.10 THz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111008 (2011)
Study on the Image Reconstruction Algorithm for Passive Human Terahertz Imaging System
Zhang Xin, Zhao Yuanmeng, Deng Chao, Zhao Yaqin, Zhu Dechong, Wang Xiaoyan, and Zhang Cunlin
In order to improve the object identification capacity of our passive human terahertz imaging system, a passive terahertz image reconstruction algorithm is put forward using deconvolution method. First the main reasons of image degradation are analyzed according to the basic imaging principle of the system. Then the orIn order to improve the object identification capacity of our passive human terahertz imaging system, a passive terahertz image reconstruction algorithm is put forward using deconvolution method. First the main reasons of image degradation are analyzed according to the basic imaging principle of the system. Then the original terahertz images are de-noised as preprocessing course. Afterwards the images are reconstructed by deconvolution method using Gaussian point spread function, so the image resolution is improved. Their grayscales are corrected. The original human terahertz images are processed and resulting images with higher definition and better object identification capability are obtained. Experimental results show that the proposed algorithm is able to effectively improve the image quality of our passive human terahertz imaging system. It can help the observers detect the contrabands hidden in the clothes of imaging subjects more quickly and accurately, which consequently strengthens the practicability of our imaging system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue s1, 111009 (2011)
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