Journals >Chinese Journal of Lasers
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2015
Volume: 42 Issue 1
49 Article(s)
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Research Article
Development of All Time Multi-Wavelength Lidar System and Analysis of Its Signal to Noise Ratio
Zhao Hu, Hua Dengxin, Di Huige, Hou Xiaolong, Yan Leijie, and Mao Jiandong
An all time multi-wavelength lidar system used for the detection of troposphere atmospheric aerosols is developed. It utilizes the beams of 1064, 532 and 355 nm emitted by a Nd:YAG laser at the frequency of 10 Hz. This multi-wavelength lidar realizes the precise separation and extraction of Mie scattering signal at ultAn all time multi-wavelength lidar system used for the detection of troposphere atmospheric aerosols is developed. It utilizes the beams of 1064, 532 and 355 nm emitted by a Nd:YAG laser at the frequency of 10 Hz. This multi-wavelength lidar realizes the precise separation and extraction of Mie scattering signal at ultraviolet, visible and infrared wavelengths. The sky background noise is strongly restrained by using aperture and interference filters, and the all time detection is achieved. The signal to noise ratios (SNR) of actual detection results are compared with simulation results at three wavelengths. It is found that the SNR at 532 nm is the lowest in the daytime detection; however, the SNR at 355 nm is the lowest in the nighttime detection. This result is consistent with the theoretical calculation. The detection height can reach 8~10 km in the daytime and 10~12 km in the nighttime, providing the actual detection SNR is 1. The results of actual detection in Xi′an in fine, cloudy and haze days show that the multiwavelength lidar can fully satisfy the need for detection of troposphere atmospheric aerosol particles at all time and under various weather conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 113001 (2015)
Data Acquisition System for Wind Lidar in the Upper Atmosphere
Gao Xin, Han Yuli, and Jin Ge
A double mode data acquisition (DMDAQ) system is developed for Doppler wind Lidar (DWL) in the upper atmosphere (15~60 km). The technical indicators of the system reach international advanced level. The DMDAQ system not only satisfies the requirements of upper atmospheric DWL with the properties of wide linear dynamic A double mode data acquisition (DMDAQ) system is developed for Doppler wind Lidar (DWL) in the upper atmosphere (15~60 km). The technical indicators of the system reach international advanced level. The DMDAQ system not only satisfies the requirements of upper atmospheric DWL with the properties of wide linear dynamic detection range and excellent spatial and temporal resolution, but also conveniently to update and incorporate in the miniaturization mobile DWL system due to its high integration and reconfigurable characteristics. In order to evaluate the performance of the DMDAQ system, the wind field observation contrast experiment is carried out. The result reveals that the Lidar observation agrees well with the radiosonde balloon in the height range of overlapping data (15~35 km). Besides, the accuracy of wind velocity is 6 m/s in the 60 km detection height according to the simultaneous DWL echo signal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 113002 (2015)
Study on Back-Scattering Light Intensity in Airborne Laser Range-Gated Imaging
Kou Tian, Wang Haiyan, Wang Fang, and Wang Ling
Based on the application of range-gated technology in the airborne laser detection imaging system, temporal relations of the parameters in the model of range gating are analyzed in detail and effective scope of atmospheric backscatter and the before- and after- pulse points of the unit section are obtained. A horizontaBased on the application of range-gated technology in the airborne laser detection imaging system, temporal relations of the parameters in the model of range gating are analyzed in detail and effective scope of atmospheric backscatter and the before- and after- pulse points of the unit section are obtained. A horizontal range-gated imaging model is established and the calculation method of back-scattering light intensity is given, and then tilt detection distance of airborne laser active imaging is revised. Based on the object-image relation of points on the scattering section, the light path diagram of detecting imaging system is built and the corresponding relationship of light intensity between scattering points and receiving points is provided. The variation regularity and distribution of light intensity on the detector under horizontal and tilt detection are gained. An outfield test platform is set up, and the relative error between measured data and simulation results is controlled within five percent, the measured data are consistent with the simulation results to a higher degree, which demonstrates the effectiveness of the built model..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 113003 (2015)
Infrared Image Contrast Enhancement Based on Haze Remove Method
Li Yi, Zhang Yunfeng, Zhang Qiang, Geng Aihui, and Chen Juan
In order to enhance the outdoor blurred infrared image contrast, an infrared image enhancement based on haze remove method is proposed. The novel algorithm optimizes and improves the visual image haze remove method which combines the characteristics of the infrared images. In order to get the transmission rate coarse eIn order to enhance the outdoor blurred infrared image contrast, an infrared image enhancement based on haze remove method is proposed. The novel algorithm optimizes and improves the visual image haze remove method which combines the characteristics of the infrared images. In order to get the transmission rate coarse estimation, a fast average filtering using three levels Gaussian pyramid operation is presented. The haze free image is recovered through self- adaptive transmission rate calculated with the statistics information of image. To deal with low luminance problem of the whole haze free image, a sectional contrast enhancement way is proposed which is capable of background suppression. Experimental results show that the enhanced infrared image has more detail information and stronger gradient than the original and has a perfect visual effects. The objective evaluation parameters illustrate that the contrast of haze free infrared image increases effectively by the proposed algorithm. The proposed algorithm can realize real time infrared image enhancement processing, as embedded platform test takes 28 ms..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 113004 (2015)
Biomedical Photonics and Laser Medicine
Real-Time Monitoring of Optical-Thermal Response of Tissue to Laser Irradiation
Wang Ling, Tu Pei, and Xu Ming′en
Previous studies and current clinical practices have applied laser therapy without effective feedback and guidance, resulting in highly variable outcomes. A method of integrating laser therapy and sweptsource optical coherence tomography (OCT) is presented to implement real-time monitoring of tissue thermal interactionPrevious studies and current clinical practices have applied laser therapy without effective feedback and guidance, resulting in highly variable outcomes. A method of integrating laser therapy and sweptsource optical coherence tomography (OCT) is presented to implement real-time monitoring of tissue thermal interaction process. OCT interference spectral signals are continuously acquired in M-mode fashion without translating the skin sample, yielding depth-resolved measurement of the same axial line as a function of time during laser exposure. Thermal injury evolution is monitored quantitatively in real time through analysis of the measured complex reflectivity, in which variations in the magnitude and changes in the phase of the complex reflectivity are extracted to detect the overall aggregate changes of the scattering centers and measure the displacement in the axial direction. Meanwhile, attenuation coefficient is obtained to determine the extent of tissue thermal damage based on OCT scattering model. The experiment results indicate that thermal coagulation and necrosis occurs under irradiation of a certain laser power with the time lasting. During the process, the thermal injury boundary propagates downward monotonically and the optical attenuation coefficient nonlinearly increases. The demonstrated correspondence with microscopy and histologically determined injury depth and magnitude suggests that these techniques may enable precise monitoring and mapping of laser thermal therapy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 104001 (2015)
Research of Pain Stimulus Induced by Dual-Wavelength Infrared Laser System
Mu Zhiming, Yang Jichun, Dong Xiaoxi, Hu Yong, Jin Wendong, and Li Yingxin
A 1940 nm and 980 nm laser pain stimulus system is built to explore the effect of baseline temperature control, oxyhemoglobin solution and laser irradiation area control on laser pain stimulus. With pig skin, a thermocouple module is used to monitor the change of the skin temperature under baseline temperature control A 1940 nm and 980 nm laser pain stimulus system is built to explore the effect of baseline temperature control, oxyhemoglobin solution and laser irradiation area control on laser pain stimulus. With pig skin, a thermocouple module is used to monitor the change of the skin temperature under baseline temperature control and 20% oxyhemoglobin solution; the shape and size of the light is controlled with the help of filters. By using the 1940 nm laser control of baseline temperature of 40 ℃ is realized and joint pain stimulus experiment is carried out with the help of the 980 nm laser. Surface temperature drop time under the condition of 20% oxyhemoglobin solution (110 ms) is much lower than the blank control (1.2 s) and air cooling heat dissipation (341 ms), proving that this is an ideal method to improve pain signal quality. Temperature field distribution with three different filters is listed, proving that the shape and size of the pain stimulus is controllable. The three technologies in the dual-wavelength pain stimulus mode mentioned above can improve the result of the laser pain stimulus and prove the feasibility and credibility of this system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 104002 (2015)
A Three-Dimensional Geometric Monte Carlo Method for Simulation of Light Propagation in Biological Tissues
Zhang Yong, Chen Bin, and Li Dong
A three-dimensional geometric Monte Carlo (GMC) method is proposed. By taking advantage of the geometrical relationship between the photon position and the interface, GMC can simulate the photon transportation in the whole domain rather than a voxel. Discrete voxels are unnecessary and the photon motion is calculated aA three-dimensional geometric Monte Carlo (GMC) method is proposed. By taking advantage of the geometrical relationship between the photon position and the interface, GMC can simulate the photon transportation in the whole domain rather than a voxel. Discrete voxels are unnecessary and the photon motion is calculated according to the geometrical optics. Therefore the optical transmission error induced by the voxel Monte Carlo (VMC) method can be eliminated. Also, the computation time consumed by GMC is dramatically shortened, and GMC is about 25 times faster than VMC with voxel grid size of 10 microns for the single vessel situation. Through the calculation of the energy deposition in a tissue model with the multi-coaxial vessel cluster, it is found that the dependence of energy absorption on the vessel distribution will recede when the vessel number increases at a certain blood volume fraction (BVF). The largest deviation of blood energy absorption is 4% with 20 vessels when BVF is 5%. This implies that artificial vascular distribution can be used to predict the real absorption characteristics with the same blood volume fraction instead of difficult measurement of real complex distribution of blood vessels, which is of great practical importance for the clinical treatment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 104003 (2015)
Holography and Information Processing
Color Image Registration Based on Colored Binary Local Invariant Descriptor
Wang Canjin, Sun Tao, Wang Rui, Wang Tinfeng, and Chen Juan
A novel local invariant feature based image registration method for color image is proposed. In the stage of feature point extraction, a new method named colored difference of features from accelerated segment test (CDoFAST) is proposed. The color invariant value of the image is calculated, and FAST extreme points in sA novel local invariant feature based image registration method for color image is proposed. In the stage of feature point extraction, a new method named colored difference of features from accelerated segment test (CDoFAST) is proposed. The color invariant value of the image is calculated, and FAST extreme points in scale space are searched. The difference of Gaussian (DoG) value around the extreme points are interpolated and fitted to determine the location and scale of the feature points. In the stage of feature vector extraction, a new colored binary local invariant descriptor (CBLID) is proposed. Its sample pattern is similar to the human visual overlap. By generating binary chain code using the statistics of orientation maps, the descriptor is invariant to rotation, scaling, illumination changes and is robust to noise. The feature vectors are matched by calculating their hamming distance and eliminating wrong matches by random sample consensus (RANSAC). Then the transform matrix between the reference image and the registered image is calculated. The experimental results indicate that the proposed method outperforms other classical methods such as scale invariant feature transform (SIFT), speed up robust feature (SURF) and DAISY in registration accuracy and cost time. The cost time of the proposed method in processing the experimental images are only 10% and 12% of that cost in SIFT..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 109001 (2015)
Contour Bag of Features Applied in Laser Active Lighting Recognition System
Sun Tao, Wang Canjin, Wang Rui, and Wang Tinfeng
A novel recognition method for laser active lighting system based on contour torque features and bag of features (BoF) is proposed. The concept of torque is introduced and a multi- scale contour torque feature region detector and a contour torque local invariant feature descriptor are proposed. The multi- scale contourA novel recognition method for laser active lighting system based on contour torque features and bag of features (BoF) is proposed. The concept of torque is introduced and a multi- scale contour torque feature region detector and a contour torque local invariant feature descriptor are proposed. The multi- scale contour torque feature region detector can extract the smallest feature region that contains the whole contours. The contour torque local invariant features can commendably represent the size, position, shape regularly of the contours, and they are also invariant to image transformation. What′ s more, the features are efficiently to compute. The contour torque local invariant features of an image with BoF algorithm is added up to generate normalized feature histogram, which is then input into the trained support vector machine (SVM) for recognition. The experimental results indicate that compared with existing laser active lighting recognition algorithm based on Hu moment and BP neural network, the recognition rate is increased by the proposed method by 7.33% in rotation transform and 19.08% in affine transform, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 109002 (2015)
Laser Devices and Laser Physics
Progress in Optical Tweezers Technology
Li Yinmei, Gong Lei, Li Di, Liu Weiwei, Zhong Mincheng, Zhou Jinhua, Wang Ziqiang, and Yao Kun
Optical tweezers, a significant application technology of the laser, are capable of trapping microscopic particles by photon linear momentum transfer. Currently, it is a vital member of the family of micromanipulation tools as well as the precision measurement instrument of pico-Newton force spectroscopy. Its inventionOptical tweezers, a significant application technology of the laser, are capable of trapping microscopic particles by photon linear momentum transfer. Currently, it is a vital member of the family of micromanipulation tools as well as the precision measurement instrument of pico-Newton force spectroscopy. Its invention does not only aroused vast applications in optics but also plays an important role, as a bridge, in the interdisciplinary research. A short overview on the basic physical principles and concepts of optical trapping over the latest 30 years is provided. Further, some important applications of optical tweezers in cell biology, single molecular biology, the physics of colloidal systems and nano- science are presented as well as the main technical features implied in these applications. Finally, we discuss and expect the perspective of application of optical tweezers in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 101001 (2015)
Laser Manufacturing
Diode-Pumped Cesium Vapor Laser with High Efficiency Output
Chen Fei, Gao Fei, Xu Yan, Xie Jijiang, Li Dianjun, Yang Guilong, and Guo Jin
Employing a fiber- coupled diode- laser with a center wavelength of 852.3 nm and a linewidth of 0.17 nm as the pump source, and using a 5 mm long cesium vapor cell with 60 kPa helium and 20 kPa ethane as laser medium, an experimental investigation of LD- end- pumped cesium vapor laser is carried out. Under an operatingEmploying a fiber- coupled diode- laser with a center wavelength of 852.3 nm and a linewidth of 0.17 nm as the pump source, and using a 5 mm long cesium vapor cell with 60 kPa helium and 20 kPa ethane as laser medium, an experimental investigation of LD- end- pumped cesium vapor laser is carried out. Under an operating temperature of 107.6 ℃ , the laser output performance is optimized by changing the reflectivity of output coupler. Using an optimized reflectivity of 48.79% , 1.16 W 894.57 nm laser is obtained at an incident continuous- wave pump power of 4.76 W, corresponding an optical- optical efficiency of 24.4% and a slopeefficiency of 28.8% , respectively.Steady cesium laser with an output power of 2.5 W is obtained under 14.1 W pulsed pump power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102011 (2015)
Investigation of Femtosecond-Laser Induced Periodic Surface Structure on Molybdenum
Wang Haozhu, Yang Fenghe, Yang Fan, Nie Meitong, and Yang Jianjun
The formation of laser induced periodic surface structure (LIPSS) on the surface of molybdenum is investigated by using 400 nm and 800 nm femtosecond lasers. In the experiment, the influences of the processing parameters, specifically pulse energy, central wavelength, pulse overlap number and the fabricating ambient onThe formation of laser induced periodic surface structure (LIPSS) on the surface of molybdenum is investigated by using 400 nm and 800 nm femtosecond lasers. In the experiment, the influences of the processing parameters, specifically pulse energy, central wavelength, pulse overlap number and the fabricating ambient on the spatial period of the LIPSS are examined. In the ambient of water, ripple-like LIPSS on molybdenum with subwavelength spatial period of only around 160 nm is fabricated successfully by using 400 nm femtosecond laser with optimized processing parameters. Besides, an improved model is proposed to account for the LIPSS formation in the water. In this model, two kinds of interference mechanism, including the interference between the incident laser and the excited surface plasmon polaritions, and the other between surface plasmon polaritions propagating opposite directions, which causes standing wave, compete with each other. The improved model agrees well with the experimental phenomena, which is of great significance for fabricating nano-structure on the surface of metals..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103001 (2015)
Comparative Study on Laser Welding with Pre-Melting Liquid Filler and Conventional Filler Wire
Peng Jin, Li Fuquan, Li Liqun, Lin Shangyang, Deng Zhou, and Zhang Furong
The laser welding with pre-melting liquid filler is developed to solve the problems, such as the reflection of incident laser energy by filler wire, and unstable keyhole in the process of laser welding with filler wire. The melting and filling characteristics of aluminum alloy filler material about laser welding with pThe laser welding with pre-melting liquid filler is developed to solve the problems, such as the reflection of incident laser energy by filler wire, and unstable keyhole in the process of laser welding with filler wire. The melting and filling characteristics of aluminum alloy filler material about laser welding with premelting liquid filler and filler wire are comparatively investigated. The results show that, in laser welding with pre-melting liquid filler, the filler wire is melt by arc, the filling stage is continuous and stable due to liquid metal wire relying on the guide role of the solid-state wire on the bottom inflow to the weld pool. It reduces the reflection of incident laser welding energy. Compared with laser welding with filler wire, the liquid filling material is far from keyhole edge so that it avoids the direct impact of fill material to the keyhole and the molten pool has a big size for the escape of bubbles. So it will help reducing the aluminum porosity. Stability of keyhole is improved in high speed welding. And it significantly improves the adaptability about the high-speed welding and wire feeding accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103003 (2015)
Simulation and Experiment of Laser Melting-Forming for Polymer Micro Component (PMC)
Tan Wensheng, Zhou Jianzhong, Zhu Weili, Huang Shu, and Men Xiankai
In order to realize molding process of polymer micro component (PMC) with high efficiency and high precision, the molding method of PMC is presented based on CO2 laser positioning irradiation. The software Comsol is used in the numerical analysis of the temperature of samples, two-dimensional (2D) and three-dimensionalIn order to realize molding process of polymer micro component (PMC) with high efficiency and high precision, the molding method of PMC is presented based on CO2 laser positioning irradiation. The software Comsol is used in the numerical analysis of the temperature of samples, two-dimensional (2D) and three-dimensional (3D) transient temperature field and distribution of samples are researched, and the influence of laser parameters on temperature variation is analyzed. The effects of processing parameters on replication quality are investigated via the development of test device and experiment. The results show that the appropriate laser parameters can meet the overall sample melting, and the higher the temperature, the better the molding precision; molding pressure is much lower than these of traditional injection molding and thermoforming. It is demonstrated that the proposed process is a feasible and effective way to laser melting-molding PMC..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103004 (2015)
Effect of Microstructure of Laser Solid Forming TC4 Titanium Alloy on Ultrasonic Parameters
Ruan Xueqian, Lin Xin, Huang Chunping, Yi Nan, Meng Yongle, and Huang Weidong
Laser solid forming (LSF) TC4 alloys and forging TC4 titanium alloy are studied. LSF-TC4 alloys are processed by different heat treatments to get different heat treatment microstructures. In order to figure out the relationship between ultrasonic parameters and microstructures, ultrasonic nondestructive testing is takeLaser solid forming (LSF) TC4 alloys and forging TC4 titanium alloy are studied. LSF-TC4 alloys are processed by different heat treatments to get different heat treatment microstructures. In order to figure out the relationship between ultrasonic parameters and microstructures, ultrasonic nondestructive testing is taken on these alloys to get ultrasonic longitudinal wave velocity and attenuation coefficient. The results show that samples with different microstructures have different velocities and attenuation coefficients. Compared with longitudinal wave velocity, attenuation coefficient is more sensitive to the change of microstructure of laser solid forming alloys..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103005 (2015)
Influence of Powder Distribution on the Al2O3 Thin-wall Ceramic Formed by Laser Engineered Net Shaping
Ma Guangyi, Wang Jiangtian, Niu Fangyong, Sun Bei, and Wu Dongjiang
Al2O3 thin- wall ceramic is formed by laser engineered net shaping and distribution of coaxial powder is obtained using tapes. A function is found to be related to the distribution of powder density. Based on this function, the influence of laser spot size and laser power on the surface morphology of thin-wall Al2O3 ceAl2O3 thin- wall ceramic is formed by laser engineered net shaping and distribution of coaxial powder is obtained using tapes. A function is found to be related to the distribution of powder density. Based on this function, the influence of laser spot size and laser power on the surface morphology of thin-wall Al2O3 ceramic is analyzed. The results show that the distribution of coaxial feeding powder is in keeping with the double Gaussian distribution. Laser spot size directly affects the powder utilization, and thereby affects the surface morphology of thin- wall parts. There is a Gaussian integral function between the laser spot size and the quantity of powder irradiated by laser beam. The results also demonstrate that high laser power can weaken the influence of powder on laser energy distribution, which can improve the surface morphology of thin- wall parts, but the surface morphology is bad if the laser power is too high. The relative density of the Al2O3 ceramic is up to 99.72% with suitable process parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103006 (2015)
Fabrication of High-Aspect-Ratio All-Silicon Grooves Using Femtosecond Laser Irradiation and Wet Etching
Li Yanna, Chen Tao, Pan An, Si Jinhai, and Hou Xun
A simple method of fabricating high-aspect-ratio all-silicon grooves using lens-focused femtosecond laser irradiation and wet etching is demonstrated. Firstly femtosecond laser is focused on silicon surface to induce structural changes inside silicon. Then laser-induced structural change regions are selectively removedA simple method of fabricating high-aspect-ratio all-silicon grooves using lens-focused femtosecond laser irradiation and wet etching is demonstrated. Firstly femtosecond laser is focused on silicon surface to induce structural changes inside silicon. Then laser-induced structural change regions are selectively removed by hydrofluoric acid (HF) etching to form high-aspect-ratio silicon grooves. Finally, optical microscope and a scanning electronic microscope are employed to characterize the morphology of the grooves, respectively. The dependences of the grooves aspect ratios on the laser irradiation parameters, such as the laser average power, scanning velocity and the lens numerical aperture, are investigated. By optimizing the laser irradiation parameters, grooves with depth of 291 μm and aspect ratio of 25.3 are produced. Compared with microscope objective lens，lens owns longer working distance, which can keep it from being polluted by the debris erupting from specimen during laser irradiation. Besides, lens has the advantages of low cost and large aperture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103007 (2015)
Laser Physics
Finite Element Analysis of Acceleration Sensitivity of Optical Cavities Supported by Soft Materials
Lü Shasha, Wang Chun, Shen Hui, Li Liufeng, and Chen Lisheng
Finite element analysis (FEA) is widely used to optimize the acceleration sensitivity of the optical cavities in Pound- Drever- Hall frequency locking method. In this process, mounting structure of the cavity is usually modeled by directly fixing small areas on the cavity or by using some rigid supports. The analysis iFinite element analysis (FEA) is widely used to optimize the acceleration sensitivity of the optical cavities in Pound- Drever- Hall frequency locking method. In this process, mounting structure of the cavity is usually modeled by directly fixing small areas on the cavity or by using some rigid supports. The analysis is extended to more practical situations where the cavity is rest on some soft supporting materials. When subjected to forces, the cavity supported by soft materials exhibits a relatively large global rotation, interfering with the calculation of the length change. A method of coordinate transformation is introduced to deduct the effect caused by the global rotation. With this procedure added, the acceleration sensitivity of a rectangularbar cavity supported by soft materials is analyzed and the results are in some differences with the results obtained by directly fixing the cavity at the same locations. The choice of the the friction coefficient and the modeling of the supporting structure in the case of using a soft material to support the cavity is also discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102001 (2015)
Research on the Frequency Stabilization Properties of Total Reflection Prism Laser Gyros
Ma Jiajun, and Jiang Junbiao
For the performance degradation of total reflection prism laser gyros in the front and rear of reset jump, the properties of frequency stabilization of total reflection prism laser gyros are studied systematically. Based on the theory of power tuning characteristic in the small jitter modulation and the serving elementFor the performance degradation of total reflection prism laser gyros in the front and rear of reset jump, the properties of frequency stabilization of total reflection prism laser gyros are studied systematically. Based on the theory of power tuning characteristic in the small jitter modulation and the serving element of frequency stabilization, a mathematic model of the frequency stabilization system in the total reflection prism laser gyros is proposed. The frequency stabilization accuracy is derived as a function of the heater voltage and rate of temperature, and the theoretical calculation formula of best reset jump threshold is given. The results show that the increase of temperature rate and the reduction of heater voltage can lead to degradation of frequency stabilization accuracy, and the best reset jump threshold increases with the environment temperature increasing, in the fixed and varied temperature environments, the fixed reset jump threshold can result in decreasing accuracy of frequency stabilization after reset jump. Using variable gain II type frequency stabilization system and setting best reset jump threshold, the performance degradation of the front and rear of reset jump can be eliminated effectively, and the gyros accuracy can be improved by over 40% . The analytic study provides an important reference for improving the performance of total reflection prism laser gyros..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102002 (2015)
Thermal Distortion of Deformable Mirror and Its Influence on Beam Quality
Hu Xiaochuan, Peng Jiaqi, and Zhang Bin
Considering the non- uniform absorption of mid-infrared film with high reflectivity, the model for the deformable mirror (DM) with high reflectivity films is built up using the finite element analysis software ANSYS. The temperature rise and thermal distortion of the DM radiated by the continuous laser beam are calculaConsidering the non- uniform absorption of mid-infrared film with high reflectivity, the model for the deformable mirror (DM) with high reflectivity films is built up using the finite element analysis software ANSYS. The temperature rise and thermal distortion of the DM radiated by the continuous laser beam are calculated, and their effects on beam quality are analyzed quantitatively. The results indicate that the nonuniform absorption of the high reflectivity film should not be neglected by using finite element analysis software. The narrower the heads spacing are, the higher the spatial frequency caused by the thermal distortions is. The effect is most obvious for the case of the incident laser beam with the peak-to-valley (PV) value of the wave distortion similar to that of the thermal distortion. For the given total absorption energy, the higher the incident laser power is, the more obvious the effect on beam quality caused by the thermal distortion is. In addition, according to different heat transfer conditions, the effect of the thermal distortion of the DM on beam quality is also discussed, and the local heat transfer mode is proposed according to the mechanism of the thermal distortion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102003 (2015)
High-Power Side-Pump Coupler and its Applications
Tan Qirui, Ge Tingwu, Dong Fanlong, Zhang Xuexia, and Wang Zhiyong
Pump coupler is the key passive optical component for the high power fiber laser. Multiple pump lights are efficiently coupled into the double- clad fiber, the required pump power can be provided for the realization of high power fiber laser. Pump coupler is the first problem to be solved for the research of the high pPump coupler is the key passive optical component for the high power fiber laser. Multiple pump lights are efficiently coupled into the double- clad fiber, the required pump power can be provided for the realization of high power fiber laser. Pump coupler is the first problem to be solved for the research of the high power fiber laser. A high power side- pump coupler is developed with the method of hydrogen- oxygen flame fusion, when the maximum pump power is 100 W, the coupling efficiency is 94% , the signal insertion loss is 0.15 dB, the additional loss is 0.2 dB, the splitting ratio of main fiber is 99%, and the directionality is 22.5 dB. A hundred-watts fiber laser with an output power of 103 W at 1080 nm is built when the maximum pump power is 185 W. Optical- optical conversion efficiency is 56% . The high power side-pump coupler can be used as the pump coupler of the hundred-watts, and even kilowatt high power fiber lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102004 (2015)
Influence and Compensation of Intra-Cavity Defocusing in Unstable Resonator Nd:YAG Thin-Disk Laser
Shang Jianli, Yu Yi, An Xiangchao, Wu Jing, and Tang Chun
Based on the self- reproduction condition of laser wavefront curvature, the influences of disk defocus on laser parameters are calculated. The overlapping efficiency decreases by 9%; the magnification rises to 2.3, and the intra-cavity loss increases to 30% due to a laser beam size mismatch when each disk has a focal lBased on the self- reproduction condition of laser wavefront curvature, the influences of disk defocus on laser parameters are calculated. The overlapping efficiency decreases by 9%; the magnification rises to 2.3, and the intra-cavity loss increases to 30% due to a laser beam size mismatch when each disk has a focal length of -100 m in the positive-branch confocal unstable resonator containing four disk with magnification of 1.8. Therefore, the optical conversion efficiency and stability are reduced significantly. Several methods of defocus compensation are compared, it is found that inserting variable- focus lens in resonator is useful in large dynamic range. In the experiment, a lens group used for compensate components with the dynamic range from - 0.016 m- 1 to 0.060 m- 1 is designed carefully and inserted into the resonator. When the pump power is 4840 W , the output power can be improved by 2.33 times compared with that under the non- compensation condition. Under this compensation, the pulse energy of 10 J can be maintained from 1 Hz to 100 Hz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102005 (2015)
Development and Performance Testing of Pulsed Excimer Laser Energy Detector
Xie Chengke, Chen Ming, Yang Baoxi, and Huang Huijie
In step and scan lithographic tools whose laser sources are excimer lasers, an energy detector is needed to monitor excimer laser pulse energy in real-time and accurately so as to realize precise exposure dose control. An energy detector, which is composed by focusing lens, an integration rod, a special crystal, a filtIn step and scan lithographic tools whose laser sources are excimer lasers, an energy detector is needed to monitor excimer laser pulse energy in real-time and accurately so as to realize precise exposure dose control. An energy detector, which is composed by focusing lens, an integration rod, a special crystal, a filter, a photodiode and a signal processing circuit, is designed. Specially, the second-order active low-pass filter is used for narrow pulse shaping so as to reduce the difficulty of the signal processing circuit. Also, an experimental setup is designed to testing the performances of the energy detector. The results show that the relative error between the measured value and the designed value of the shaped pulse for the energy detector is about 3% , and the response time of the energy detector can meet the application of pulse energy measurement with pulse′ s repetition rate up to 4 kHz. Secondly, with a double-beam ratiometric method which is used to remove excimer laser pulse energy fluctuation, the performances of the energy detector are tested; the energy detector′s repeatability is 0.26%; within a dynamic range of pulse energy from 0.1 μJ to 1 μJ per pulse, the linear fit is V=0.59841E-0.01508 and R2=99.976% . Experimental results prove that the secondorder active low-pass filter can be used for pulse shaping; the repeatability and the linearity of the designed energy detector are perfect, and the energy detector can be used to accurately measure the energy of high repetition rate pulse for excimer lasers in lithographic tools..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102006 (2015)
Experimental Study on High Brightness 1018 nm Ytterbium Doped Fiber Laser
Wang Yanshan, Sun Yinhong, Ma Yi, Li Tenglong, Gao Qingsong, Tang Chun, and Zhang Kai
High power 1018 nm ytterbium doped fiber laser system is constructed. Output characteristics of 1018 nm laser with the length of gain fiber, the reflectivity of fiber Bragg gratings (FBG) and the diameter of core/cladding are experimentally investigated. It is found that the laser at short wavelength will get bigger gaHigh power 1018 nm ytterbium doped fiber laser system is constructed. Output characteristics of 1018 nm laser with the length of gain fiber, the reflectivity of fiber Bragg gratings (FBG) and the diameter of core/cladding are experimentally investigated. It is found that the laser at short wavelength will get bigger gain by reducing the length of gain fiber for ytterbium doped fiber laser, 1018 nm laser can be obtained by shortening the length of gain fiber. Increasing the fiber bragg grating reflectivity and core/cladding area ratio are available approach to suppress the amplified spontaneous emission (ASE) gain and increase the laser efficient. A record output power more than 150 W at 1018 nm is obtained through using the domestic double cladding ytterbium doped fiber, with an optical- optical conversion efficiency of 71% , the ASE is suppressed efficiently..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102007 (2015)
Investigation on Plasma Electron Density Distribution with Finite Holographic Interferometry
Lei Lan, Cao Na, Cao Liang, Xu Qing, Han Changcai, and Duan Baojun
Laser-induced air plasma is produced by focusing an 1064 nm Nd:YAG laser beam (spot diameter of 100 μm , pulse energy of 60 mJ, pulse width of 200 ps). The electron density distribution is diagnosed by holographic interferometry. The displacement isoline is obtained from infinite interferogram, and the electron densityLaser-induced air plasma is produced by focusing an 1064 nm Nd:YAG laser beam (spot diameter of 100 μm , pulse energy of 60 mJ, pulse width of 200 ps). The electron density distribution is diagnosed by holographic interferometry. The displacement isoline is obtained from infinite interferogram, and the electron density distribution is calculated from finite interferogram. The results indicate that the ion and electron in laser-induced air plasma form in an olivary shape, which has symmetrical distribution in the vertical direction but unsymmetrical distribution in the horizontal direction, and the maximal electron density is about 1018 cm-3..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102008 (2015)
Design of End-Pumped Double Cladding Nd:YAG Planar Waveguide Laser Amplifier
Wang Juntao, Wang Xiaojun, Zhou Tangjian, Wang Dan, Tong Lixin, Hu Hao, and Gao Qingsong
A high power laser amplifier with high efficiency and compactness is designed. The thermal stress of symmetrical double cladding planar waveguide with Nd:YAG as its core is analyzed theoretically, and the maximum pump light intensity is also obtained. For different inner cladding thicknesses, the optimized pump sourcesA high power laser amplifier with high efficiency and compactness is designed. The thermal stress of symmetrical double cladding planar waveguide with Nd:YAG as its core is analyzed theoretically, and the maximum pump light intensity is also obtained. For different inner cladding thicknesses, the optimized pump sources and coupling system are achieved with the simulation of the TracePro software. In order to control the laser mode effectively, the 100 μm thickness of the core is set. The inner cladding and outer cladding are pure YAG and sapphire, respectively, with the waveguide of the dimension of 60 mm×10 mm×2 mm. The pump light from the laser diode array is coupled into the waveguide from two ends, two surfaces of the outer cladding are welded with two copper heat sinks for heat transfer. The seed light is coupled into the waveguide from one end and amplified for single pass. By theoretical calculation, the output of 1322 W can be obtained when the pump power is 3384 W and the seeder power into the waveguide is 0.1 W, with the optical-optical efficiency of 39%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 102009 (2015)
Materials and Thin Films
Laser Welding-Brazing Characteristics of Dissimilar Metals Mg/Ti with Al Interlayers
Tan Caiwang, Gong Xiangtao, Li Liqun, and Feng Jicai
The metallurgical bonding and reliable joining of Mg/Ti dissimilar metals are restricted by their nonreactive and immiscible characteristics. To overcome this problem, laser lap joining of Mg/Ti with addition of Al interlayer is carried out. Well appearances are obtained by adjusting the welding parameters. Elemental dThe metallurgical bonding and reliable joining of Mg/Ti dissimilar metals are restricted by their nonreactive and immiscible characteristics. To overcome this problem, laser lap joining of Mg/Ti with addition of Al interlayer is carried out. Well appearances are obtained by adjusting the welding parameters. Elemental distribution across the interface and bonding mechanism are studied. The results indicate that wettability of Mg/Ti is improved with the help of Al interlayer, and thus metallurgical bonding is accelerated. When the thickness of Al interlayer is 50 μm , the shear force reaches 1010N/cm, which is 1.8 times as much as that without Al interlayer. The interfacial microstructure indicates that AlTi3 phase forms at the direct laser irradiation zone, while α - Ti is at the zone around it at the interface. The second phases in the weld zone increase with the increase of thickness of Al interlayer. The tensile- shear force decreases when network structure is formed in the weld zone..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 103002 (2015)
Research to Mechanics Erosion Effect of Laser Irradiating Glass/Epoxy Composites
Peng Guoliang, Zhang Xianghua, Gao Yinjun, and Yan Hui
Basing the experiment phenomenon, a model and criterion for simulating mechanics erosion process have been developed for laser irradiating glass/epoxy composite. The mechanics erosion process has been divided into two processes of delamination and layer fracture. A thermo mechanical model can be used until composite deBasing the experiment phenomenon, a model and criterion for simulating mechanics erosion process have been developed for laser irradiating glass/epoxy composite. The mechanics erosion process has been divided into two processes of delamination and layer fracture. A thermo mechanical model can be used until composite delamination appears. Then plates and shell theory can be used for simulating layer fracture. The experiment results agree well with the simulation value , and that shows the model is reasonable. The simulation results indicate that the mechanics erosion process is very important for laser ablation effect, and the ablation energy can be reduced greatly by the process; the ablation efficiency can be higher with lower laser intense..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 106001 (2015)
Study on Electrode Waveguide Dielectric Film for High Power Radio Frequency Slab CO2 Laser
Yang Weihong, Yuan Jinkun, Wang Du, Chen Yifeng, and Tang Xiahui
To solve the problems of the high power radio frequency (RF) slab CO2 laser surface oxidation by copper electrode discharge and RF discharge electronic sputtering which leads to rough electrode surface, an uniform glow discharge and serious optical loss and so on. The magnetron sputtering coating technology is used forTo solve the problems of the high power radio frequency (RF) slab CO2 laser surface oxidation by copper electrode discharge and RF discharge electronic sputtering which leads to rough electrode surface, an uniform glow discharge and serious optical loss and so on. The magnetron sputtering coating technology is used for laser electrode surface plating Al, and then anodic oxidation into Al2O3 waveguide dielectric film, based on the effect of anomalous dispersion and high temperature resistant ability of Al2O3 waveguide dielectric film. The influence of magnetron sputtering process on the film structure is analyzed; the reflectivity of the electrode coating to CO2 laser is measured and the discharge experiment is tested. The results show that when the sputtering power is 250 W, the compact film structure can be obtained; Al2O3 thin films with thickness of 6 μm , have the highest reflectance peak of 75% to CO2 waveguide laser wavelength of 10.6 μm ; The laser output power at a 30% duty cycle is 700 W, in the duty cycle of 60% reaches 1300 W after electrode coating..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 107001 (2015)
Mid-Infrared Properties of Oxide Coatings Prepared by Ion Beam Sputtering Deposition
Li Ding, and Xiong Shengming
Single layer Al2O3，Nb2O5 films are prepared by ion beam sputtering deposition (IBSD). Optical constants are measured by infrared variable angle spectroscopic ellipsometer (IR- VASE). Surface topography and roughness of these films are investigated by atomic force microscopy (AFM). 2.7 μm dielectric mirror is prepared uSingle layer Al2O3，Nb2O5 films are prepared by ion beam sputtering deposition (IBSD). Optical constants are measured by infrared variable angle spectroscopic ellipsometer (IR- VASE). Surface topography and roughness of these films are investigated by atomic force microscopy (AFM). 2.7 μm dielectric mirror is prepared using Nb2O5 and Al2O3 as high and low refractive index materials. The environmental stability of single layer films is tested. The results show that asdeposited films have relatively high refractive index, low extinction coefficient, excellent surface morphology and extremely low scattering loss. There is no water absorption in these films which can lead to great increase in extinction coefficient at the 2.7 μm band. The measured reflectance of 2.7 μm Nb2O5/Al2O3 mirror is 99.63% , close to theoretical value. All the films have passed the environmental tests，showing that oxide coatings fabricated by IBSD are stable and durable in hash environment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 107002 (2015)
Measurement and Metrology
Study of Birefringence Dispersion Based on Liquid Crystal Variable Retarder
Li Kewu, Wang Zhibin, Zhang Rui, and Yu hui
In order to realize a liquid crystal variable retarder (LCVR) to precisely control the phase delay for different wavelengths of the incident light and expand its application advantages in the field of optical information and optical measurements, its birefringence dispersion characteristics are studied and analyzed. FiIn order to realize a liquid crystal variable retarder (LCVR) to precisely control the phase delay for different wavelengths of the incident light and expand its application advantages in the field of optical information and optical measurements, its birefringence dispersion characteristics are studied and analyzed. Firstly, according to the index ellipsoid theory, LCVR birefringence dispersion of the incident light is matched with Cauchy dispersion; Secondly, retardance for 532, 635, 670 nm laser is measured, which changes with the value of drive voltage; Finally, the above three measurements are analyzed, the coefficients about empirical formula of Cauchy dispersion are solved, and a calibration method of dispersion used a normalizing way is established and verified with a 650 nm laser. Experimental results show that LCVR produces birefringence dispersion for different wavelength incident light. For 650 nm laser, the retardance deviation between experimental result and dispersion calibration is given not more than 0.007λ , which proves the calibration method is accurate and feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 108001 (2015)
Active Control Technology to Correct the Quality of the Grating Wave-Front
Yang Chao, Yu Haili, Zhang Shanwen, Yu Hongzhu, Li Xiaotian, and Tang Yuguo
Diffracted wave- front quality is one of the most important performance indexs for ruled gratings. For mechanically ruled gratings, positioning accuracy of the groove directly affects the wave- front quality of the gratings. The mathematical relationship between the inherent errors of the ruling machine which includingDiffracted wave- front quality is one of the most important performance indexs for ruled gratings. For mechanically ruled gratings, positioning accuracy of the groove directly affects the wave- front quality of the gratings. The mathematical relationship between the inherent errors of the ruling machine which including the error of groove position, error of yaw and wave-front error of the gratings is developed, and the impact of various errors on the wave- front quality is analyzed. According to the error of groove position and error of yaw, a measure optical path is designed based on double-frequency laser interference, and a method to correct the error of groove position and error of yaw is proposed using piezoelectric actuator. According to the correction method, a double workbench is designed, and the ruling experiments for the size of 80 mm × 60 mm and groove density of 194 line/mm are carried out. The results show that the diffracted wave-front error of the ruled grating is reduced from 0.23λ to 0.093λ (λ = 632.8 nm) , and testing quality of the groove by atomic force microscope meets the requirement of the theoretical design..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 108002 (2015)
Study on Hartmann Wavefront Analyzer Calibration Method
Wang Yanping, Wang Qianqian, and Ma Chong
Based on the principle of Hartmann wavefront analyzer (HWA), the necessity of calibrating pinholes array to CCD spacing LH is clarified. The method of calibrating LH with known gradient plane wave, and tracing gradient value to the point source accuracy displacement, is presented and discussed. According to this calibrBased on the principle of Hartmann wavefront analyzer (HWA), the necessity of calibrating pinholes array to CCD spacing LH is clarified. The method of calibrating LH with known gradient plane wave, and tracing gradient value to the point source accuracy displacement, is presented and discussed. According to this calibration method, a HWA is calibrated and corrected value of LH is given. The calibrated HWA measures three spherical wavefronts with different curvature radii. Compared to ideal spherical wavefronts, wavefront measurement accuracy is up to λ/35 , and wavefront aberration peak- valley (PV) value is λ/7 . The experimental results show that calibrated value of HWA is accurate, and given calibration method is effective and feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 108003 (2015)
Adjustability and Realization of Compensation Adjustment Type Laser Elliptic Polarizer
Song Lianke, Niu Mingsheng, Han Peigao, Hao Dianzhong, and Ma Lili
The elliptical polarizer, which is designed using linear polarizer and wave plate combination, is a very important polarization modulation device. It can meet the need of the different wavelengths or ellipticity angle through the orientation compensation and adjustment of the various components. And it has high practicThe elliptical polarizer, which is designed using linear polarizer and wave plate combination, is a very important polarization modulation device. It can meet the need of the different wavelengths or ellipticity angle through the orientation compensation and adjustment of the various components. And it has high practical value as it has wide wavelength tuning range and the stability output state. According to the elliptic matrix and Poincare Sphere Theory, there exist regular relationship among the devices′ orientation, phase and the wavelength. The different wavelength polarization state is affected by the matching condition. This design consists of a broadband transmission polarizing prism and two identical zero order plates. The prism can ensure the stability polarization direction of the incident light and, the wave plate can select the wavelength and change the ellipticity angle. The results show that the material properties limit the application range of the elliptical polarizer. The designed mica wave plate, whose continuous adjustable range is 700 nm, can be applied in the range of 300 ~1400 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 108004 (2015)
Accuracy Enhancement Method for Coordinate Control Field Based on Space Length Constraint
Xie Zhengwei, Lin Jiarui, Zhu Jigui, and Ren Yu
In order to achieve global orientation and accuracy control in large space geometric measurement, precise three-dimensional coordinate control field need to be established. Using a laser tracker to establish coordinate control field by single station is the most effective means recently. But in face of higher accuracy In order to achieve global orientation and accuracy control in large space geometric measurement, precise three-dimensional coordinate control field need to be established. Using a laser tracker to establish coordinate control field by single station is the most effective means recently. But in face of higher accuracy in local area, coordinate transform error between stations must be reduced in the process of global orientation, and accuracy of control field in the region must be enhanced. By using high accuracy ranging interference of laser tracker, multiple spatial length standards are constructed with carbon fiber rods and target ball seats, and arranged flexibly in the desired region in the space. In the process of using a laser tracker to make redundant measurement of control points by multi-station, length standards are added as constraints to overcome space occlusion and optimize tracker angle measurement error, further improve the coordinate accuracy of control points used to construct length standard, thus enhance the local field measurement accuracy. The experimental results show that accuracy of global orientation is better than 0.04 mm in the range of 10 m with this method, which meets high accuracy requirement of large space geometric measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 108005 (2015)
Optical Communication
Investigation of Structure Design and Transmission Characteristic of GeSbSe Photonic Crystal Waveguides
Wang Xianwang, Zhang Wei, Han Jintao, Wei Fengjuan, Zhang Peiqing, Wu Yuehao, Zhang Liang, Dai Shixun, and Xu Tiefeng
The plane wave expansion method is used in this paper to calculate the photonic band gap based GeSbSe and the relationship between the photonic band gap and the air holes (or media column) in photonic crystal waveguides is studied. Combining with the operating wavelength of photonic crystal waveguides, the period of 50The plane wave expansion method is used in this paper to calculate the photonic band gap based GeSbSe and the relationship between the photonic band gap and the air holes (or media column) in photonic crystal waveguides is studied. Combining with the operating wavelength of photonic crystal waveguides, the period of 500 nm and the radius of air holes of 150 nm in a triangular lattice are determined. The twodimensional finite difference time domain method is induced to simulation the transmission characteristics both in straight and 60° bend waveguides, and the results show that the transmission efficiency in straight waveguides is much higher than those in bend waveguides. The reasons may be there are different propagation modes between straight parts and bend parts in photonic crystal waveguides. Finally, the structures of 60° bend waveguides are optimized and the results show that there is an excellent transmission efficiency in a wide range of wavelengths in photonic crystal waveguides based GeSbSe..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 105001 (2015)
Investigation on Fabrication and Characteristics of Four Ports Optical Microfiber
Yu Yang, Zhang Xueliang, Xie Jiehui, Song Zhangqi, and Meng Zhou
In this paper, optical microfiber coupler (OMC) with wavelength scale of waist region which is obtained with two twisted optical fibers by direct draw method is manufactured and experimentally studied. Experimental results show that coupling capacity will almost disappear when the diameter of the waist region is less tIn this paper, optical microfiber coupler (OMC) with wavelength scale of waist region which is obtained with two twisted optical fibers by direct draw method is manufactured and experimentally studied. Experimental results show that coupling capacity will almost disappear when the diameter of the waist region is less than 2.5 μm . And the OMC will serve as the four ports optical microfiber (FPOM) with the capacity of combining and splitting light. We analyze and distinguish the optical properties between OMC and FPOM by the method of online monitoring the sample drawing process，the stability measurement and the wavelength scanning. Especially, an all optical modulation method based on thermal effect caused by light absorption is adopted for measuring the optical modulation capacity of the OMC and FPOM. The stable optical transmission properties of the FPOM are verified, and the splitting ratio is almost insensitive to wavelength, temperature, transmission optical power fluctuation and other physical parameters. Such properties ensure that the FPOM can be utilized to multiplex and integrate micro photonic devices. The OMC with structure optimization can be employed to sense the temperature and vibration, as well as potentially being used as an all optical modulator..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 105002 (2015)
High Dynamic Range Microwave Photonic Link Based on Dual-Wavelength Dual-Parallel Modulation
Li Xianghua, Yang Chun, Chong Yuhua, and Zhou Zhenghua
A linearization method based on dual-wavelength dual-parallel modulation is proposed to enhance the dynamic range of microwave photonic link. The exacerbation of spurious-free dynamic range of linearized link due to the drift of the optical power of lasers is simulated. The simulation results show that this linearizatiA linearization method based on dual-wavelength dual-parallel modulation is proposed to enhance the dynamic range of microwave photonic link. The exacerbation of spurious-free dynamic range of linearized link due to the drift of the optical power of lasers is simulated. The simulation results show that this linearization method can be performed by using commercially available devices. Furthermore, the performances of a single-Mach-Zehnder modulator (MZM) intrinsic link and a dual-wavelength dual parallel modulation linearized link are compared in the experiment. The measurement results show that 1.5 dB enhancement of compression dynamic range and 15.6 dB of improvement spurious-free dynamic range are achieved after linearization. The spurious-free dynamic range of linearized link is up to 122.5 dB · Hz4/5. In a word, this linearization method is a good alternative for improving the dynamic range of optical links..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 105003 (2015)
A Novel Method on Modulation and Demodulation of All Fiber Optical Current Transformer
Ouyang Kang, Hong Xiaobin, Wu Jian, and Lin Jintong
A kind of fiber optical current transformer which employs a novel method on modulation and demodulation is proposed. The system controls the phase modulator with a return- to-zero square wave, and implements the analog coherent demodulation with a sine wave which acts as the local oscillator signal, and fulfills the cuA kind of fiber optical current transformer which employs a novel method on modulation and demodulation is proposed. The system controls the phase modulator with a return- to-zero square wave, and implements the analog coherent demodulation with a sine wave which acts as the local oscillator signal, and fulfills the current closed loop measurement by digital signal processing (finite impulse response filter, moving average filter) of acquired data to generate step wave. The result of the experiment suggests that the method can realize the closed loop measurement of large current, meet 0.2 level of IEC 60044-8:2002 standard when rated current is 1000 A at room temperature, and has the practical application value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 105004 (2015)
Experimental Research on Wireless Optical Communication Based on 16PSK Subcarrier Modulation
Chen Dan, Ke Xizheng, Zhang Tuo, and Dai Lu
Atmospheric turbulence and the weather conditions are bound to affect the quality of optical signal in wireless optical communication, increase the system error rate and reduce the communication distance. 16 binary phase shift keying (16PSK) subcarrier modulation block in wireless optical communication system is designAtmospheric turbulence and the weather conditions are bound to affect the quality of optical signal in wireless optical communication, increase the system error rate and reduce the communication distance. 16 binary phase shift keying (16PSK) subcarrier modulation block in wireless optical communication system is designed based field programmable gate array (FPGA) and AD9788. Subcarrier modulated wireless optical communication system is established, and communication experiments are performed under four weather conditions (cloudy, sunny, rainy, snowy). The constellation diagram, error rate, eye diagram and the power spectrum on different weathers are analyzed and contrasted at the receiver. The phase convergent information in cloudy is better than other weathers, and the bit error rate is about 2.9 × 10-3, while phase information is dispersive in snowy. Power spectrum curve has the largest power at the carrier frequency under four kinds of weather, and the spectrum curves under cloudy and light rain weathers are smoother and less jitter. The experimental results prove that the wireless optical communication on subcarrier 16PSK modulation is feasible to realize point to point communication..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 105005 (2015)
Rapid Communications
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 119001 (2015)
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 119002 (2015)
Optical Design and Fabrication
Investigation of Flexible Element in Passive Athermalisation
Xu Yao, Huang Yifan, and Chang Jun
In order to realize the athermalisation of infrared optical system, an finite element analysis (FEA) model is established to analysize the contact stress of the lens and sensitivity of the structure. First, based on the athermal requirements of the optical system, the concept of the flexible pressure ring is introducedIn order to realize the athermalisation of infrared optical system, an finite element analysis (FEA) model is established to analysize the contact stress of the lens and sensitivity of the structure. First, based on the athermal requirements of the optical system, the concept of the flexible pressure ring is introduced. Then, thermal deformation analysis is made on the flexible elements. After that, we design the flexible elements based on the sensitivity analysis, which gets that the flexible elements can reduce the contact stress of the lens and makes the choice of the lens sear materials more easily. Finally, the flexible elements is introduced to the triplet system. The simulation results indicate that the modulation transfer function (MTF) of the triplet system is above 0.5 under the use of flexible elements when the spacial frequency of MTF is 10 lp/mm. The defocus of the ordinary pressure ring under 60 ℃ and -20 ℃ are 4.765 mm and -6.312 mm respectively while the flexible are 1.261 mm and -1.563 mm respectively. The use of the flexible elements can meet the athermal requirements of the infrared system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 116001 (2015)
Effects of Rogue Particles on Scratches of Phosphate Neodymium Glass Polishing
Cao Jun, Yang Minghong, Wei Chaoyang, Dun Aihuan, Gu Jianxun, Xu Xueke, and Shao Jianda
In order to study the effects of different rogue particles on the scratches, and establish the relationship between the rogue particle size and the scratch topography, experiments have been carried out. During the process of phosphate neodymium polishing, three different sizes of corundum, cerium oxide agglomerate and In order to study the effects of different rogue particles on the scratches, and establish the relationship between the rogue particle size and the scratch topography, experiments have been carried out. During the process of phosphate neodymium polishing, three different sizes of corundum, cerium oxide agglomerate and polished powder are introduced as rogue particles. Data of scratch topography is analyzed statistically. The results show that brittle scratches, plastic scratches and mixed scratches all exist, among which brittle scratches account for a large proportion; scratches caused by cerium oxide agglomerate and polished powder are shallow and few, while scratches caused by corundum are deep and many; the scratch density and scratch length caused by corundum of different sizes increase with the increasing of particle size; distribution of scratch widths caused by different sizes of corundum is similar to the distribution of the size of rogue particle, shown as Gaussian distribution. Using the model proposed by T. Suratwala, mechanism of scratch generating during phosphate neodymium glass polishing is investigated. It is illustrated that the width and length of scratches increase with the increasing of rogue particle size..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 116002 (2015)
Machining Error Compensation System Design of Optical Parametric Amplification Crystals Tiling
Zhang Junwei, Yan Wei, Lin Donghui, Wu Wenlong, Wang Xiao, Chen Liangming, and Fu Xuejun
Tiling crystals technology can solve the problem of nonlinear crystal aperture limit in the process of optical parametric chirped pulse amplification (OPCPA). The crystal machining error compenstation is one of the most important problems need to be solved in crystals tiling. The beam quality influenced by tiling crystTiling crystals technology can solve the problem of nonlinear crystal aperture limit in the process of optical parametric chirped pulse amplification (OPCPA). The crystal machining error compenstation is one of the most important problems need to be solved in crystals tiling. The beam quality influenced by tiling crystals machining error is analyzed and the machining error compensation method of tiling crystals is designed. According to the method, an active array mirror system is designed and machined, which is used to compensate the tiling crystal machining error. The feasibility and stability of tiling crystal machining error compensation system is tested, which indicates that the system can satisfy the crystal tiled requirement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 116003 (2015)
Remote Sensing and Sensors
A New Adaptive Fusion Method Based on Saliency Analysis for Remote Sensing Images
Zhang Libao, and Zhang Jue
In remote sensing image fusion, these different object regions have different demands on the spatial and spectral resolution. A new adaptive fusion method based on saliency analysis for the remote sensing image is proposed. The multi-scale spectral residual (MSR) analysis model is introduced to divide the remote sensinIn remote sensing image fusion, these different object regions have different demands on the spatial and spectral resolution. A new adaptive fusion method based on saliency analysis for the remote sensing image is proposed. The multi-scale spectral residual (MSR) analysis model is introduced to divide the remote sensing image into the salient regions with the rich texture and edge information and the non- salient regions with the less texture and edge information. Two different fusion algorithms are applied to the two kinds of areas. The window mean intensity hue saturation (IHS) transform can be used in salient regions with the rich texture and edge information, such as urban areas and roads, to retain more texture and edge information while the wavelet transform can be used in non-salient areas, such as farmlands and mountains, to retain more spectral information. The experimental results show that the new algorithm can obtain the salient regions as urban areas and roads with more texture and edge information and non- salient areas as farmlands and mountains with more spectral information. The new method has more theory and application value in further research of remote sensing image fusion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 114001 (2015)
Research of the Unmanned Plane Airborne Lidar System Strip Stitching Method
Zhao Dawei, Pei Hailong, Ding Jie, and Zhang Cheng
In order to avoid the misregistration in three- dimensional (3D) space between flight strips caused by the system error and random error in airborne light detection and ranging (LiDAR) and improve the data accuracy, a data- driven“six parameters”strip adjustment method is selected for the realization of airborne LiDAR In order to avoid the misregistration in three- dimensional (3D) space between flight strips caused by the system error and random error in airborne light detection and ranging (LiDAR) and improve the data accuracy, a data- driven“six parameters”strip adjustment method is selected for the realization of airborne LiDAR system strips registration. An improved 3D normal distributions transform (3D- NDT) is used for the registration of strips to obtain the transformation parameters between the strips on the basis of the analysis of the data of LiDAR. A detailed comparison between the popular iterative closest point (ICP) algorithm and the 3D normal distributions transform is presented through specific experiment. The result shows that this approach can realize flight strip registration rapidly with high accuracy and stronger robustness, which is very suitable for practical engineering..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 114002 (2015)
Simulation in the Time Domain and Time-Frequency Analysis for Coherent Doppler Wind Lidar
Bai Xue, Guo Pan, Chen Siying, Zhang Yinchao, Chen He, and Bu Zhichao
An atmospheric slices time domain signal generation algorithm model (feuilleté model) is proposed to simulate the signal under non-stationary atmospheric conditions. The wind inversion by means of timefrequency analysis is introduced, and the algorithm processing of signals simulated under non-stationary wind modeAn atmospheric slices time domain signal generation algorithm model (feuilleté model) is proposed to simulate the signal under non-stationary atmospheric conditions. The wind inversion by means of timefrequency analysis is introduced, and the algorithm processing of signals simulated under non-stationary wind model is studied. Based on the actual system parameters, the echo signals are simulated under conditions of linear wind shear and national aeronautic and space administration (NASA) typical wind shear model, respectively. Wind inversion by analyzing the distribution of peak energy in the time-frequency domain after the application of Wigner-Ville transformation on the simulated signal is got. And in this process, the fluctuation of wind inversion, which results from speckle noise, cross terms and other factors, can be reduced by accumulating multiple time-frequency transforms of pulses. The results show that, wind inversion is obtained quickly and directly by utilizing time-frequency analysis methods and without division of range gate in detection zone. The fluctuation of wind inversion decreases after the processing of accumulation and average, and the similarity between wind inversion and input wind speed is improved significantly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 114003 (2015)
Spectroscopy
Study on Cervical Cancer Oxyhemoglobin Using Near-Infrared Surface-Enhanced Raman Spectroscopy
Xiong Yang, Si Minzhen, Gao Fei, and Zhang Deqing
A new type of Ag nanofilm with high efficiency is prepared and used here, acting as a near-infrared surface-enhanced Raman spectroscopy (NIR-SERS) substrate to detect oxyhemoglobin (OxyHb) for 22 cervical cancer patients and 22 healthy females. NIR-SERS results show that there is striking spectral difference of the OxyA new type of Ag nanofilm with high efficiency is prepared and used here, acting as a near-infrared surface-enhanced Raman spectroscopy (NIR-SERS) substrate to detect oxyhemoglobin (OxyHb) for 22 cervical cancer patients and 22 healthy females. NIR-SERS results show that there is striking spectral difference of the OxyHb between healthy females and cervical cancer patients. Meanwhile, principal component analysis (PCA) combined with independent sample T-test analysis is employed to analyze the measured NIR-SERS spectra, and it is found that the measured NIR-SERS spectra of the two groups are separated into two distinct clusters in terms of the sensitivity of 86.4% and the specificity of 86.4%. Tentative assignments of the Raman bands of the measured NIR-SERS spectra are also performed, and the results suggest that cancer specific changes at molecular level, including pyrrole ring and vibration mode of the OxyHb molecules are significant. The NIR-SERS detection of OxyHb for cervical cancer patients based on PCA combined with independent sample T-test is expected to develop into a new diagnostic tool for cervical cancer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 1, 115001 (2015)
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