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2015
Volume: 52 Issue 12
39 Article(s)
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Atmospheric Optics and Oceanic Optics
Research on Earth′s Atmosphere Limb Background Infrared Radiation Characteristic
Shi Bo, Li Rui, Liu Chunsheng, and Wu Xingwu
The infrared radiation characteristics of the environment for spacecraft play a significant role in the infrared characteristics of the spacecraft. Thus the study on infrared radiation of aircraft background is essential. The regime which only consists of the regional atmospheric climate system in the field is called lThe infrared radiation characteristics of the environment for spacecraft play a significant role in the infrared characteristics of the spacecraft. Thus the study on infrared radiation of aircraft background is essential. The regime which only consists of the regional atmospheric climate system in the field is called limb background in the view of the atmosphere system of the earth. Based on moderate spectral resolution atmospheric radiation transmittance algorithm (MODTRAN) atmospheric radiation model, the atmospheric radiation transmission theory is used to establish the limb infrared radiation model. Limb background infrared radiations are calculated at all latitudes in the typical wavelength ranges of 3~5 μm and 8~14 μm , including the seasons of winter and summer. The results show that the main factors affecting the limb background infrared radiation are tangent altitude, latitude, season, aerosol and wavelength range. These provide theoretical supports for the detection of limb background infrared radiation..
Laser & Optoelectronics Progress
- Publication Date: Nov. 13, 2015
- Vol. 52, Issue 12, 120101 (2015)
Wavelength Choice for Infrared Laser Based on Atmospheric CO2 Concentration Wide Spectrum Measurement
Lin Hong, Zhou Chuanlin, Zhao Na, and Huang Panli
By analyzing the ultra fine atmospheric CO2 absorption spectrum, the infrared laser wavelength can be choiced for detecting the atmosphere CO2 concentration. It can provide the basis for a wide spectrum infrared lidar. The spectrum of wide spectrum infrared laser is much wider than the differential absorption lidar, anBy analyzing the ultra fine atmospheric CO2 absorption spectrum, the infrared laser wavelength can be choiced for detecting the atmosphere CO2 concentration. It can provide the basis for a wide spectrum infrared lidar. The spectrum of wide spectrum infrared laser is much wider than the differential absorption lidar, and it has no use for high frequency locking technology. Also, this technology can avoid differential absorption lidar measurement error by the on wavelength shift. By analyzing the water vapour absorption spectrum, super luminescent diode (SLED)′s luminescent spectrum and InGaAs infrared detector′s response spectrum, the wide spectrum laser center wavelength is 1572 nm and the spectral range is 1568~1575 nm in theory. By the experimental laser source,the results show that the center wavelength is 1571 nm, the spectral range is 1564~1578 nm, the output power is 0.01 mW. This laser can avoid the influence by the water vapour absorption, and it is simple, low cost and easy to build. It can help for the development of the atmosphere CO2 concentration detecting by the wide spectrum infrared lidar..
Laser & Optoelectronics Progress
- Publication Date: Nov. 28, 2015
- Vol. 52, Issue 12, 120102 (2015)
Fiber Optics and Optical Communications
Energy Analysis of Spaceborne Underwater Laser Detection
Li Yingchao, Hu Yuan, Wang Chao, and An Yan
Using spaceborne platform for underwater laser detection has many advantages, including a large coverage area, high detection efficiency, good mobility, good concealment, and fast information transmission, however its implementation is difficulty greatly. In order to detect the target information reflecting the charactUsing spaceborne platform for underwater laser detection has many advantages, including a large coverage area, high detection efficiency, good mobility, good concealment, and fast information transmission, however its implementation is difficulty greatly. In order to detect the target information reflecting the characteristics effectively, laser pulse signal needs to be through space channel, atmospheric channel, and water channel, and that is all bidirectional transmission, the link is very complicated. Through the establishment of laser transmission model and analysis of the link energy loss, the theory feasibility of spaceborne underwater lasertarget detection is verified..
Laser & Optoelectronics Progress
- Publication Date: Nov. 25, 2015
- Vol. 52, Issue 12, 120601 (2015)
Cassegrain Transceiver Antenna Based on Fiber Array
Ke Xizheng, Lei Sichen, and Wang Tianyu
Cassegrain antenna can be easily installed and its structure is much simpler. However, the blind area caused by the secondary mirror costs the transmission lost. A novel transceiver antenna based on Cassegrain telescope, which makes full use of Cassegrain antenna effective area (area outside part) as transmitting, is pCassegrain antenna can be easily installed and its structure is much simpler. However, the blind area caused by the secondary mirror costs the transmission lost. A novel transceiver antenna based on Cassegrain telescope, which makes full use of Cassegrain antenna effective area (area outside part) as transmitting, is proposed. To effectively avoid the influence of blind zone, the annular distribution and off-axis transmission of four GRIN-lens glued fiber structures transverses insteads Gaussian distribution and along-axis transmission of the lasers. The large aperture plastic fiber is used as the receiving method to improve the coupling efficiency and it makes transmitting align with receiving easily. The test results show that the transceiver antenna is easy to align at a low transmission loss costs. It satisfies the requirements of the general free space optical communication (FSO) system, and ultimately achieves transceiver integrated in one Cassegrain antenna..
Laser & Optoelectronics Progress
- Publication Date: Nov. 03, 2015
- Vol. 52, Issue 12, 120602 (2015)
Tunable Bi-Directional Optical Add-Drop Multiplexer Based on Fiber Bragg Grating
Yang Kang, Li Guoyu, Li Yan, and Jia Sumei
A tunable bi-directional optical add-drop multiplexer (Bi-OADM) based on fiber Bragg grating (FBG) is proposed and demonstrated. The center wavelength of the optical add-drop multiplexer (OADM) is tuned without chirp by using open and closed piezoelectric ceramic (PZT) separately. The tunable range can reach 6 nm, whilA tunable bi-directional optical add-drop multiplexer (Bi-OADM) based on fiber Bragg grating (FBG) is proposed and demonstrated. The center wavelength of the optical add-drop multiplexer (OADM) is tuned without chirp by using open and closed piezoelectric ceramic (PZT) separately. The tunable range can reach 6 nm, while the range of commercial eight wavelengths multiplexing system is 5.6 nm. The experiment shows a good reproducibility in the voltage load and unload curves when using open loop in small voltage and using closed loop in big voltage (more than 80 V). Employing optical switches and alternate-path switching scheme, the bi-directional transmission can make one-direction light path normally transmit when the other direction light path is fail in the ring network, which can greatly improve the reliability of OADM. The experimental results indicate that the tunable Bi-OADM shows a low insert loss (4 dB)..
Laser & Optoelectronics Progress
- Publication Date: Nov. 13, 2015
- Vol. 52, Issue 12, 120604 (2015)
LCOS-Based Flexible Grid 1′32 Wavelength Selective Switch
Chen Ran, Chen Xiao, Chen Ying, Gao Yunshu, Chen Genxiang, and Wang Yiquan
In recent years, reconfigurable optical add drop multiplexers (ROADM) and multiple-dimensions optical cross-connection (OXC), as the essential devices of next-generation dynamic optical networks, have been attracted great interests by research institutions and relevant industry. 1′N wavelength selective switch (WSS) isIn recent years, reconfigurable optical add drop multiplexers (ROADM) and multiple-dimensions optical cross-connection (OXC), as the essential devices of next-generation dynamic optical networks, have been attracted great interests by research institutions and relevant industry. 1′N wavelength selective switch (WSS) is one of the key components in current and next generation ROADM. However, most WSS modules of the present have the disadvantages of complex optical system, large insertion loss and high crosstalk, as well as the imperfection of the port number and the channels number. So, a high port-count 1×32 WSS based on liquid crystal on silicon (LCoS) technology is demonstrated, which has a flexible- tuning bandwidth. By uploading phase holograms at the corresponding locations on the LCoS device, the system allows a certain wavelength of the entire C-band DWDM channels to be switched from any input port to any output port. Experimental results demonstrate the insertion loss is around 5 dB to 25 dB. The 3 dB bandwidth of signal is 40 GHz at the grid of 100 GHz and the bandwidth is tunable from 50 GHz continuously with the step of 1 GHz. The research can provide the theory and experiment foundation for the development of M×N WSS in the future..
Laser & Optoelectronics Progress
- Publication Date: Nov. 03, 2015
- Vol. 52, Issue 12, 120605 (2015)
Experimental Research on Fiber Optical Sensing System Based on Interferometer with Polarization Switching
Liu Yue, Jiang Peng, Ma Lina, Tang Kai, and Hu Zhengliang
The basic principle of polarization switching to eliminate polarization- induced fading in fiber optic interferometers is studied. A theoretical model is constructed and the complex method of complex is introduced to solve the problem that four signals compose one signal. Theoretical analysis and simulation show that pThe basic principle of polarization switching to eliminate polarization- induced fading in fiber optic interferometers is studied. A theoretical model is constructed and the complex method of complex is introduced to solve the problem that four signals compose one signal. Theoretical analysis and simulation show that polarization switching can eliminate polarization-induced fading. An experimental system based on non-balanced Michelson interferometer is built. Using phase generation carrier (PGC) modulation technology to demodulate signal, the antipolarization effect of the four-way polarization switching is tested by experiment. The results show that the birefrigent effect of the lead fiber can be eliminated after the signal is composed. After four signals compose one signal in the experiment, its visibility can be a stable level of 0.838. The result keeps with the visibility of Michelson interferometer under ideal condition, which proves the feasibility of polarization switching in elimination of polarization-induced fading..
Laser & Optoelectronics Progress
- Publication Date: Nov. 28, 2015
- Vol. 52, Issue 12, 120606 (2015)
Analysis of the Polarization Characteristic of a Satellite-to-Ground Laser Communication Optical System
Wang Chao, Jiang Lun, Dong Keyan, An Yan, and Jiang Huilin
To the satellite-to-ground (STG) optical communication, the circular polarization laser is an optimum choice for the information transmission. Firstly, the influence factors of the polarization characteristics of the optical system are analyzed by the Fresnel formula and the Jones Matrix. Then the structure of a practiTo the satellite-to-ground (STG) optical communication, the circular polarization laser is an optimum choice for the information transmission. Firstly, the influence factors of the polarization characteristics of the optical system are analyzed by the Fresnel formula and the Jones Matrix. Then the structure of a practical STG laser communication transmitting optical system and the designed transmittance curves of several different bandpass filtering films in the system are given. Propagation of the linear polarization laser in the optical system is simulated by the optical software ZEMAX. The results indicate that the beam splitters and mirrors on a 45° tilt make the greatest contributions to the polarization state transform. Ordinary depolarization film can only prove that the power pcomponent and s-component transmittances are identical. But the phase delay of p-light and s-light still exist, which can make the polarization state change. By adjusting the direction of the incident light vector to the incident plane, the instrument polarization error induced by the optical system can be reduced to the minimum..
Laser & Optoelectronics Progress
- Publication Date: Oct. 25, 2015
- Vol. 52, Issue 12, 120607 (2015)
Holography
Method on Controllable Reconstruction of Fresnel Computer-Generated Hologram Watermark for Digital Hologram
Chen Jiazhen, Zheng Zihua, Ye Feng, Lian Guiren, and Xu Li
A method on controllable reconstruction of Fresnel computer-generated hologram watermark for digital hologram has been proposed. Complex amplitude distribution is obtained by calculating discrete Fresnel transformation of the watermark object wave in the holographic plane, and the watermark and the diffraction distribuA method on controllable reconstruction of Fresnel computer-generated hologram watermark for digital hologram has been proposed. Complex amplitude distribution is obtained by calculating discrete Fresnel transformation of the watermark object wave in the holographic plane, and the watermark and the diffraction distribution signal are double-random-phase modulated to improve security. The encryption data are reprocessed and modulated to get real-coded CGH watermark. The encoded signal after the discrete cosine transformation is added to medium frequency component with certain intensity. The watermark can be blind extracted without the host hologram signal. The results show that the approach behaves good invisibility and is robust to many attacks such as cropping, JPEG compression, filtering, rotation, scaling, etc. The method has good digital reconstruction quality for both the host hologram and the watermark. The size and position of the watermark can be easily adjusted by changing the magnification and the reconstructed wave. The zero-order image elimination of the host hologram does not affect the extraction of the watermark..
Laser & Optoelectronics Progress
- Publication Date: Nov. 25, 2015
- Vol. 52, Issue 12, 120901 (2015)
Image Processing
Color Image Segmentation Based on Improved Internal Activity Multi-Channel Pulse Coupled Neural Networks
Wang Mengjun, Guo Lin, Wang Xia, and Hao Ning
In order to make full use of the image color information and overcome the traditional single channel pulse coupled neural network information loss in the process of image segmentation. A multi-channel image segmentation method is proposed, input channel of each color component is established for RGB color space. So mulIn order to make full use of the image color information and overcome the traditional single channel pulse coupled neural network information loss in the process of image segmentation. A multi-channel image segmentation method is proposed, input channel of each color component is established for RGB color space. So multi-channel pulse coupled neural networks are formed which contains three input channels. Internal activity is modified based on coupled averaging of each input channel, dynamic threshold changes with exponential ascent, each component of the three-dimensional euclidean inverse distance matrix is calculated as the connection weighting coefficient matrix for each channel, and maximum entropy is adopted as evaluation criteria. Experiments are carried out based on standard color images, optimal parameters of multi-channel pulse coupled neural networks are selected according to test results. Experimental results show that more particulars of color image are preserved by color image segmentation based on multi-channel pulse coupled neural networks. Average value of maximum entropy increases by 3% relatively，image segmentation effect is improved while cost time is reduced more than 80%..
Laser & Optoelectronics Progress
- Publication Date: Nov. 26, 2015
- Vol. 52, Issue 12, 121001 (2015)
Dual-Band Image Fusion Using Visual Attention Extraction with Multiple Windows
Li Meng, Hua Weiping, and Zhao Jufeng
For the visible and infrared images, dual-band image fusion enhancement is achieved with visual attention extraction under multiple windows. The visual attention map is obtained using local frequency tuned idea, and this attention map simulates human visual system to give different visual weights to different areas andFor the visible and infrared images, dual-band image fusion enhancement is achieved with visual attention extraction under multiple windows. The visual attention map is obtained using local frequency tuned idea, and this attention map simulates human visual system to give different visual weights to different areas and pixels. The method for multiple window-based visual attention maps extraction is designed, which could highlight feature information with different sizes. Based on multi-scale visual attention maps, dual-band image fusion enhancement is achieved. Using dual-band image of demonstration experiments, and combining with both subjective and objective assessment to evaluate various fusion methods. The experimental results demonstrate that the proposed method can efficiently reserving details and meet the need for human visual at the same time, and has faster operating rate..
Laser & Optoelectronics Progress
- Publication Date: Nov. 13, 2015
- Vol. 52, Issue 12, 121002 (2015)
Imaging Systems
Application of Bilateral Filtering Algorithm on Terahertz Confocal Scanning Image Denoising
Yang Yongfa, and Li Qi
Due to the addition of confocal pinholes and the unstable output of terahertz laser currently, the performance of terahertz confocal scanning microscopic imaging is not high. The bilateral filtering algorithm is applied to the image denoising of transmission type terahertz confocal scanning microscopic imaging. ThroughDue to the addition of confocal pinholes and the unstable output of terahertz laser currently, the performance of terahertz confocal scanning microscopic imaging is not high. The bilateral filtering algorithm is applied to the image denoising of transmission type terahertz confocal scanning microscopic imaging. Through the experiment, the bilateral filtering parameters are calculated to fit this situation. Moreover, through the comparison of the filtering performance with median filtering, average filtering and open operation filtering, it is proved that the bilateral filtering algorithm is feasible to apply for image denoising of transmission type terahertz confocal scanning microscopic imaging..
Laser & Optoelectronics Progress
- Publication Date: Nov. 13, 2015
- Vol. 52, Issue 12, 121101 (2015)
Instrumentation, Measurement and Metrology
Four-Wave Lateral Shearing Interferometry System for Transient Wavefront Measurement
Zhu Wenhua, Chen Lei, Gu Chenfeng, Zheng Donghui, Li Jinpeng, and Cao Hui
In order to detect the three-dimensional distribution of transient wavefront, a shearing interferometric measurement system with common path configuration is proposed. The system uses a chessboard grating and aperture to divide the wavefront under test into four replicas with shear. Each two of the replicas are coherenIn order to detect the three-dimensional distribution of transient wavefront, a shearing interferometric measurement system with common path configuration is proposed. The system uses a chessboard grating and aperture to divide the wavefront under test into four replicas with shear. Each two of the replicas are coherent to form an interferogram with high carrier frequency. According to the transport of intensity equation and Fourier optics, the theoretical model of shearing interferometric measurement system is established and the wavefront under test is reconstructed by Fourier transform algorithm. A calibration method of shear is proposed. The design of chessboard grating is given by discussing linear carrier frequency and diffraction efficiency of the grating. Experimentally the proposed system is applied to measure transient wavefront, and automatic measurement with high precision is achieved. Peak-to-valley (PV) value, root-mean-square (RMS) value and Zernike fitting coefficient of the measured result are in good agreement with those obtained by SID4 wavefront sensor. This system can be applied to transient wavefront measurement..
Laser & Optoelectronics Progress
- Publication Date: Nov. 20, 2015
- Vol. 52, Issue 12, 121201 (2015)
Lasers and Laser Optics
Effects of High-frequency Microforging on the Laser Cladding Layer prepared on the 304 Stainless Steel Substrate
Zhu Hongmei, Yin Quan, and Peng Rushu
The laser cladding layer on the 304 stainless steel surface is modified by a high-frequency microforging process. The microstructure and phase constitution of the laser cladding layer before and after the high-frequency microforging treatment are characterized by using optical microscopy and X-ray diffraction. The micrThe laser cladding layer on the 304 stainless steel surface is modified by a high-frequency microforging process. The microstructure and phase constitution of the laser cladding layer before and after the high-frequency microforging treatment are characterized by using optical microscopy and X-ray diffraction. The microhardness distribution and corrosion property of the counterparts are examined by Vickers microhardness tester and the electrochemical work station, respectively. The results show that laser cladding layer is of a broken dendritic microstructure and refined grain size after microforging, while there is no obvious change in the phase constitution. The microhardness of the microforged area is greatly enhanced with an affected depth of 0.65 mm. The average microhardness of the surface is improved by about 30% and the microhardness increment decreases gradually with the increasing distance from the top of the cladding layer. The corrosion resistance of the laser cladding layer is improved by nearly two folds after microforging..
Laser & Optoelectronics Progress
- Publication Date: Nov. 26, 2015
- Vol. 52, Issue 12, 121401 (2015)
Investigation on Microhole Formation Characteristics for Pulsed Laser Drilling of Aluminum Alloy 5052 Sheets
Ren Naifei, Xia Kaibo, and Wang Houxiao
The parameter control method is utilized to carry out the experimental investigation for the single pulse laser drilling of aluminum alloy 5052 sheets. Effects of pulse width, pulse recurrence frequency, and defocusing amount on microhole formation characteristics for laser drilling are achieved and the reasonable procThe parameter control method is utilized to carry out the experimental investigation for the single pulse laser drilling of aluminum alloy 5052 sheets. Effects of pulse width, pulse recurrence frequency, and defocusing amount on microhole formation characteristics for laser drilling are achieved and the reasonable process parameter ranges are obtained, which can be the technical reference of process optimization and parameter selection for the pulsed laser drilling of aluminum alloy 5052. It shows that the laser pulse width can obviously influence the microhole diameter. Besides, the alteration of the pulse recurrence frequency may also result in the change of the drilled microhole diameter, that is, the entry hole diameter increases with the pulse repetition frequency. However, the radial size alteration for the exit hole shows a reverse trend. In addition, less tapered microholes with relatively small diameters can be drilled through appropriately decreasing pulse repetition frequency, reducing defocusing amount, and increasing pulse width..
Laser & Optoelectronics Progress
- Publication Date: Oct. 20, 2015
- Vol. 52, Issue 12, 121402 (2015)
Laser-Diode Pumped Nd∶GdVO4 Actively Q-Switched Passively Mode-Locked Laser
Wang Xubao, Wu Dan, Xiaolei, Liu Jun, and Mi Qinggai
Two kinds of LD pumped Nd: GdVO4 crystal actively Q- switched passively mode- locked lasers are reported. Using self-mode-locking and semiconductor saturable absorber output coupler mode-locking respectively combined with electro-optic actively Q-switch, stably Q-switched mode-locked laser is obtained. The actively QswTwo kinds of LD pumped Nd: GdVO4 crystal actively Q- switched passively mode- locked lasers are reported. Using self-mode-locking and semiconductor saturable absorber output coupler mode-locking respectively combined with electro-optic actively Q-switch, stably Q-switched mode-locked laser is obtained. The actively Qswitched self-mode-locked laser has a Q-switched envelope repetition rate of 3 kHz and a pulse duration of about 1.2 μs, while the self-mode-locked pulses within the Q-switched envelope have a repetition rate of 159 MHz and an estimated pulse duration of 963 ps. The actively Q-switched semiconductor saturable absorber output couple mode-locked laser has a Q-switched envelope repetition rate of 10 kHz and a pulse duration of about 300 ns, while the repetition rate of mode-locked pulses within the Q-switched envelope is 159 MHz and the pulse duration is about 491 ps. The mathematical expressions of the nonlinear loss of self-mode-locking equivalent fast saturable absorber and semiconductor saturable absorber output coupler are presented respectively. Using the fluctuation mechanism, the rate equations of electro- optic actively Q- switched self- mode- locked laser and electro- optic actively Qswitched semiconductor saturable absorber output couple mode-locked laser are presented. Through the comparison of the output characteristics and the rate equations for these two Q-switched mode-locked lasers, the superposition of the two modulation effects is analysed..
Laser & Optoelectronics Progress
- Publication Date: Nov. 13, 2015
- Vol. 52, Issue 12, 121403 (2015)
Bending Deformation and Surface Characteristics of 2024 Aluminum Alloy Processed by Laser-Induced Shock Wave
[in Chinese], and [in Chinese]
2024 aluminum alloy is deformed by shock waves which are induced by pulse laser of nanosecond duration. Bending deformation, residual stress and surface morphology are studied on laser-shocked specimens. It is found that laser power density and coverage rate strongly influence plastic strains and its distributions, whi2024 aluminum alloy is deformed by shock waves which are induced by pulse laser of nanosecond duration. Bending deformation, residual stress and surface morphology are studied on laser-shocked specimens. It is found that laser power density and coverage rate strongly influence plastic strains and its distributions, which drive specimens to curve. The laser-shocked surfaces becomes uniform with coverage rate increasing. For specimens of thickness more than 4mm, curvature radius are proportional to specimen thickness, and the compressive residual stresses on shock surface gets more relaxed with arc height increasing..
Laser & Optoelectronics Progress
- Publication Date: Oct. 25, 2015
- Vol. 52, Issue 12, 121405 (2015)
Characters of Orthogonal Polarized He-Ne Laser with Integrated Y-shaped Cavity Research
Gong Mengfan, Xiao Guangzong, Fu Yangying, and Zhang Bin
To improve the laser performance, an orthogonal polarized He-Ne laser with integrated Y-shaped cavity is designed after modifying the cavity structure, the gain region and the processing technology of polarizing beam splitter. Cavity structures and operating principles of the laser are described, and the mode, power, lTo improve the laser performance, an orthogonal polarized He-Ne laser with integrated Y-shaped cavity is designed after modifying the cavity structure, the gain region and the processing technology of polarizing beam splitter. Cavity structures and operating principles of the laser are described, and the mode, power, lock-in features, frequency difference stability of the laser are measured. Detailed performance enhancements are shown, especially the frequency difference stability. Comparisons are presented to traditional laser with detached Y-shaped cavity. The results show that the frequency difference between two cavities can be linearly adjusted by changing the voltage of the piezoelectric transducer in the P-cavity. Compared with the detached Y-shaped cavity laser, the output power of the integrated laser is improved to 647 μW, the lock-in frequency difference is reduced to 12 MHz, the range of frequency difference is improved to 12~1038 MHz, while the frequency difference stability is improved to 1.2×105 Hz..
Laser & Optoelectronics Progress
- Publication Date: Oct. 25, 2015
- Vol. 52, Issue 12, 121406 (2015)
Materials
Influence of Material Absorption Spectrum and Band Gap of Two Dimensional Photonic Crystal
Miao Lei, Shi Jiaming, and Zhao Dapeng
The influence of the two dimensional photonic crystals on the absorption of materials and the substrate is studied. By using the transfer matrix method along with a certain direction of lattice photonic crystal, the energy band structure based on the transfer matrix method is solved. Researches show that absorption canThe influence of the two dimensional photonic crystals on the absorption of materials and the substrate is studied. By using the transfer matrix method along with a certain direction of lattice photonic crystal, the energy band structure based on the transfer matrix method is solved. Researches show that absorption can bring new band gap to a frequency which doesn′t have band gaps, while extending the range of the original band gap, and TE wave is more impacted than TM wave by the absorption..
Laser & Optoelectronics Progress
- Publication Date: Nov. 26, 2015
- Vol. 52, Issue 12, 121601 (2015)
Band Gap Properties of Two-Dimensional Square Lattice Photonic Crystal Composed of Duck-Shaped
Liu Juan, Tang Jiyu, Chen Yan, Liu Yang, Dong Guiren, and He Youqing
Complete band gap of two-dimensional photonic crystal structure with four different scatterers (circle, hourglass, wing, duck) are simulated. The symmetry of the four scatterers in turn reduce. The results show that the duck-shaped scatterers of photonic crystals are more likely to produce complete band gap than other Complete band gap of two-dimensional photonic crystal structure with four different scatterers (circle, hourglass, wing, duck) are simulated. The symmetry of the four scatterers in turn reduce. The results show that the duck-shaped scatterers of photonic crystals are more likely to produce complete band gap than other shapes of scatterers. The influence of dielectric constant and the geometric parameter of duck-shaped scatterer on the complete band gap is studied. The results show that when the dielectric constant is 26.6, the big semicircular radius is 0.331 μm , and the radius of small semicircular is 0.535 times that of the big semicircular, the value of complete band gap reaches the maximum value of 0.0583 (wa/2πc)..
Laser & Optoelectronics Progress
- Publication Date: Nov. 07, 2015
- Vol. 52, Issue 12, 121602 (2015)
Medical Optics and Biotechnology
Optical Detection System of Centrifugal Microfluidic Chip for Biochemical Analysis
Wang Yu, Hao Peng, Wu Junfeng, Xu Yang, Deng Yongbo, and Wu Yihui
Taking advantage of the centrifugal microfluidic chip for biochemical analysis, an optical detection system based on absorbance detection technology is designed. The effect of the poor light output stability of xenon flash lamp on test results is reduced by dual wavelength detection. The chip is located precisely by syTaking advantage of the centrifugal microfluidic chip for biochemical analysis, an optical detection system based on absorbance detection technology is designed. The effect of the poor light output stability of xenon flash lamp on test results is reduced by dual wavelength detection. The chip is located precisely by synchronous trigger positioning in the detection process. The effect of sampling error on the test results is also analyzed. The test results show that the absorbance repeatability of the system is 0.0994% by dual wavelength detection; the locating error is extremely small, it is 0.1429% by synchronous trigger positioning; and the sampling error is lower than 2%, which meets the requirements of national standards. The system has the advantages of simple structure, easy integration, and stable and reliable test results, it is promising in medical diagnosis.microfluidic chip.
Laser & Optoelectronics Progress
- Publication Date: Nov. 20, 2015
- Vol. 52, Issue 12, 121701 (2015)
Phase Microscopy Imaging Method Based on Common-Path without Micro-Objective
Chen Yingzhou, Ji Ying, Xie Ming, Xu Yuanyuan, Han Hao, Bu Min, and Wang Yawei
Phase microscopic imaging technology has an important application significance in morphological identification as well as classification of biological cells. An interferometric imaging method is introduced, which is based on a high stability common-path interference system. In this approach, a reflecting mirror is emplPhase microscopic imaging technology has an important application significance in morphological identification as well as classification of biological cells. An interferometric imaging method is introduced, which is based on a high stability common-path interference system. In this approach, a reflecting mirror is employed to divide one beam into two parts. Then interferogram can be obtained by the overlap of these two beams. It is worth pointing out that, the interferogram can be amplified by means of geometrical magnification of the light instead of microobjective. Furthermore, the on-axis, off-axis and micro off-axis phase microscopy images can be obtained by controlling the angular position of the reflecting mirror. Then the structure of the sample can be acquired by phase retrieval. The method is suggested to be feasible by theoretical analysis and experiment result, which can provide a approach to phase microscopy imaging..
Laser & Optoelectronics Progress
- Publication Date: Dec. 03, 2015
- Vol. 52, Issue 12, 121702 (2015)
Simulation of Light Absorption in Tumor-Embedded Prostate for Transurethral Light Delivery by Diffusing Light
Peng Dongqing, and Li Hui
Photoacoustic imaging has recently emerged as a promising imaging modality for prostate cancer. Knowledge of absorbed light distribution in prostate tissues is essential since the distribution characteristics of absorbed light energy will influence the imaging depth and range of photoacoustic imaging (PAI). In this papPhotoacoustic imaging has recently emerged as a promising imaging modality for prostate cancer. Knowledge of absorbed light distribution in prostate tissues is essential since the distribution characteristics of absorbed light energy will influence the imaging depth and range of photoacoustic imaging (PAI). In this paper, a tumor-embedded prostate optical model was established. Light absorption distribution patterns of the tissue model through trans-urethral laser illumination using cylindrical diffusing light (CDL) and spherical diffusing light (SDL) were studied based on the Molecular Optical Simulation Environment (MOSE). In addition, the influence of laser energy and absorption coefficient of tumor on the light absorption in tumor was demonstrated. The results show that laser illumination from urethral allows the prostate tissues to obtain more efficient light absorption. The light absorption distribution of tumors irradiated by CDL has a relatively uniform characteristic in a large range, with its value around the light source less than that of SDL. Laser energy and tumor absorption coefficient has linear effect on the light absorption of tumor, which is consistent with the Beer Law. The conclusions will be helpful to optimize the laser source and to improve the imaging depth in a photoacoustic imaging system..
Laser & Optoelectronics Progress
- Publication Date: Oct. 27, 2015
- Vol. 52, Issue 12, 121703 (2015)
Nonlinear Optics
Broadband Frequency Doubling of Er-Fiber Mode-Locked Laser in BBO Crystal
Yang Sheng, Huang Xiaojun, Wu Zhaohui, Qiu Rong, Wang Junbo, and Li Chao
The BBO crystal has insensitivity to the wavelength near 1550 nm where mode-locked Er-fiber lasers operate through the analysis of the Sellmeier equations, which can be used for broadband frequency doubling of femtosecond Er-fiber laser. Split-step Fourier method is used to numerically solve the coupled wave equations The BBO crystal has insensitivity to the wavelength near 1550 nm where mode-locked Er-fiber lasers operate through the analysis of the Sellmeier equations, which can be used for broadband frequency doubling of femtosecond Er-fiber laser. Split-step Fourier method is used to numerically solve the coupled wave equations of frequency conversion. The conversion efficiency and the output spectral bandwidth with the length of the crystal under different power densities and different durations of the fundamental pulse are obtained. On this basis, citations are made to select the best size of BBO crystal. Compared with the small signal approximation, this method is applicable more widely, which can be used to choose the crystal under different power densities..
Laser & Optoelectronics Progress
- Publication Date: Nov. 28, 2015
- Vol. 52, Issue 12, 121901 (2015)
Numerical Study on Autocorrelation of Noise-Like Pulse in Fiber Lasers
Jin Xinxin, Li Lei, Luo Jiaolin, Ge Yanqi, Zhang Qian, and Zhao Luming
The autocorrelation characteristics of the noise-like pulse generated from fiber laser are investigated using numerical analysis. Numerically calculated autocorrelation traces agree with experimental results. By changing the parameters, it is found that the pedestal and the spike reflect the average pulse width and intThe autocorrelation characteristics of the noise-like pulse generated from fiber laser are investigated using numerical analysis. Numerically calculated autocorrelation traces agree with experimental results. By changing the parameters, it is found that the pedestal and the spike reflect the average pulse width and intrapulse width, respectively. Increasing intra- pulse number in a noise- like pulse leads to a smaller spike- topedestal intensity ratio, while the width of the pedestal and the spike are not obviously influenced. Numerical analyses show that the contrast ratio of the interferometric autocorrelation trace less than 8∶1, which is detected in experiment, is determined by the noise-like pulse width ,pulse chirp and scan range..
Laser & Optoelectronics Progress
- Publication Date: Nov. 13, 2015
- Vol. 52, Issue 12, 121902 (2015)
Optical Design and Fabrication
Influence of Adjustable Supporting Force on Surface Shape of Optical Element
Wu Zhihui, Wang Dongping, Hua Yangyang, Ni Mingyang, and Dong Lijian
Adjustable optic mount is commonly used in the structure design of high precision optical system. Surface shape of optical element influenced by the supporting force adjustment is researched. Mechanical model of the adjustable mount is established, deformation of optical element is calculated with finite element methodAdjustable optic mount is commonly used in the structure design of high precision optical system. Surface shape of optical element influenced by the supporting force adjustment is researched. Mechanical model of the adjustable mount is established, deformation of optical element is calculated with finite element method, and the surface shape is fitted with Zernike polynomials. The analysis results in different working conditions show that the root mean square (RMS) of surface shape is minimized when optical element is under uniform support; when supporting force changes, it causes linear variety of RMS and main Zernike polynomial coefficients of surface shapewhich is independent at the initial working condition of optical element. Finally, sensitivity matrix of Zernike polynomial coefficients changed by every supporting force is established, then estimation of surface shape due to support force adjustment in a new random working condition is made, the estimated result is similar to the finite element analysis surface shape, and the error of RMS is less than 0.3%, so the estimating method is able to guide the design and assembly of adjustable optic mount..
Laser & Optoelectronics Progress
- Publication Date: Oct. 25, 2015
- Vol. 52, Issue 12, 122201 (2015)
Realization of LED Solar Simulator Matching and Irradiance Unevenness
Zhu Kongshuo, Sun Jiangang, Li Guohua, and Ma Xiaoguang
Six kinds of high power LED which have peak wave length of 460, 525, 625, 730, 850, 940 nm respectirdy. The light source of the LED solar simulator meets the intensity of 1 solar irradiation on the effective radiation surface, and also achieves the level of spectral matching. In this design, the irradiation nonuniformiSix kinds of high power LED which have peak wave length of 460, 525, 625, 730, 850, 940 nm respectirdy. The light source of the LED solar simulator meets the intensity of 1 solar irradiation on the effective radiation surface, and also achieves the level of spectral matching. In this design, the irradiation nonuniformity index is six wavelength combination of LED light source in the effective irradiated surface inhomogeneity of energy. In order to reduce nonuniformity on the effective irradiated surface of the LED solar simulator, we combine design process with optical characteristics of LED light emitting angle, and pointedly realize multiple converging optical systems. Through the control of LED light source array, we have achieved 160 mm×160 mm A-level standard of non-uniformity on effective irradiation area. According to the international standard, the standard of the LED solar simulator reaches the level of the AAA level solar simulator standard..
Laser & Optoelectronics Progress
- Publication Date: Nov. 07, 2015
- Vol. 52, Issue 12, 122202 (2015)
Thermal Sensitivity Analysis of High Resolution Space Video Camera
Li Kai, An Yuan, Li Zongxuan, Kong Lin, and Guo Junli
With the improving requirements of satellite′s imaging quality, it often requires plenty of thermal control resources to meet the requirements of the space camera′s temperature. Because the resources of small satellite are rare, it is important to study the thermal sensitivity of the camera component, rational distribuWith the improving requirements of satellite′s imaging quality, it often requires plenty of thermal control resources to meet the requirements of the space camera′s temperature. Because the resources of small satellite are rare, it is important to study the thermal sensitivity of the camera component, rational distribution of thermal control resource and how to improve the image quality. First, researching status and methods of thermal-structural-optical integrated analysis are introduced. Then, the finite element model of space video camera is established to analyze the influence of thermal deformation of the components under the temperature load on the optical system′s imaging quality. Last, contrast analysis of the results under different operating conditions are finished and the influence of the components under the temperature load on the optical system′s imaging quality is achieved. The results show that reducing temperature load of every operating condition whose influence to the modulation transfer function is on the top six can make the image quality meet the requirement. It provides a reference to the thermal control design of the video camera..
Laser & Optoelectronics Progress
- Publication Date: Oct. 25, 2015
- Vol. 52, Issue 12, 122203 (2015)
Hyperspectral Imaging of Human Gastric Parietal Cells Based on Narrowband AOTF
Gao Qiang, Zhang Chunguang, Wang Hao, and Huang Junfeng
The nonlinear acousto-optic tunable filter (AOTF) based on TeO2 is a new device which can convert the ultrasonic and optical wave. It has small volume, low weight, large aperture and incident aperture, rapid coordination in a wide spectral range, and good diffraction efficiency. The AOTF based on TeO2 is used for hyperThe nonlinear acousto-optic tunable filter (AOTF) based on TeO2 is a new device which can convert the ultrasonic and optical wave. It has small volume, low weight, large aperture and incident aperture, rapid coordination in a wide spectral range, and good diffraction efficiency. The AOTF based on TeO2 is used for hyperspectral imaging experiments. The conversion between diffraction of light central wavelength and ultrasonic frequency in the experiment is very close to the theoretical result. A hyperspectral microscopic imaging system, combined with an inverted optical microscope, which can exhibit histologic section of human parietal cells under different light central wavelength and different ultrasonic frequency on AOTF is designed. The experimental results show that the image quality is very good. By comparing images under different ultrasonic wave frequency and light centeral wavelength, more details and difference of cells can be found. A method to acquire hyperspectral images of cells under different light central wavelength is provided, the method is easy to operate and the results are easy to analyze..
Laser & Optoelectronics Progress
- Publication Date: Oct. 27, 2015
- Vol. 52, Issue 12, 122205 (2015)
Optical Design of Transmission Volume Holographic Grating Raman Spectrometer
He Zhenlei, Lu Qipeng, Ding Haiquan, and Gao Hongzhi
Aiming at resolution and weak signal detection of Raman spectrometer, an optical system for Raman spectrometer is designed using transmission volume holographic grating. The transmission volume holographic grating is designed based on the coupled wave theory of Kogelnik. The diffraction efficiency of the grating at blaAiming at resolution and weak signal detection of Raman spectrometer, an optical system for Raman spectrometer is designed using transmission volume holographic grating. The transmission volume holographic grating is designed based on the coupled wave theory of Kogelnik. The diffraction efficiency of the grating at blaze wavelength reaches 90% and the average efficiency is higher than 80% in the range of 800~1000 nm. According to the aperture and field of view, Tessar-type split triplet is used as the basic structure of the focusing lens. The spot diagram root mean square (RMS) radius of the optimized system is less than 6 μm and the resolution reaches 0.3 nm. The aberration of the transmission grating system designed in this paper is small, which leads to high spectral resolution. By using volume holographic grating with high efficiency and low stray light, the system will perform better in weak signal detection. The system can be used in Raman spectrometer and improve its resolution and weak signal detection ability..
Laser & Optoelectronics Progress
- Publication Date: Nov. 03, 2015
- Vol. 52, Issue 12, 122206 (2015)
Tolerance Analysis of High-Numerical Aperture Extreme Ultraviolet Lithographic Objective
Sun Yuanyuan, Li Yanqiu, and Cao Zhen
High-numerical aperture (NA>0.45) extreme ultraviolet lithography is a promising candidate for 11 nm node lithography, and the tolerances of the objective system are rigorous due to high resolution image. The singular value decomposition (SVD) of the sensitivity matrix from sensitive mirrors is used to select efficiHigh-numerical aperture (NA>0.45) extreme ultraviolet lithography is a promising candidate for 11 nm node lithography, and the tolerances of the objective system are rigorous due to high resolution image. The singular value decomposition (SVD) of the sensitivity matrix from sensitive mirrors is used to select efficient compensators for an extreme ultraviolet (EUV) lithographic objective with a numerical aperture of 0.50. The method requires that the amounts of configuration parameters is less than that of the aberration parameters, so the sensitive mirrors are confirmed and the sensitivity matrix is obtained by the configuration parameters of the sensitive mirrors. Then the sensitive and efficient compensators are selected to relax the other tolerances and compensate the worse of image quality by using the SVD of the sensitivity matrix. Using the above method, eight compensators are selected and other tolerances are assigned. Result shows that the RMS wavefront error of the objective system is less than 0.5 nm in the probability of 97.7% and the most rigorous tolerances are in the range of micron and microradian respectively..
Laser & Optoelectronics Progress
- Publication Date: Nov. 25, 2015
- Vol. 52, Issue 12, 122207 (2015)
Remote Sensing and Sensors
Application of Robust Estimation to Airborne Lidar Point Cloud Filtering
Liu Zhiqing, Li Pengcheng, Zhang Baoming, Guo Haitao, and Ding Lei
Airborne Lidar point cloud data filtering is one of the difficulties and emphases in the study of Lidar data post-processing, and also the primary problem needed to be solved. Least squares adjustment is used to fit block terrain in traditional moving curved fitting filtering method, but this method is sensitive to outAirborne Lidar point cloud data filtering is one of the difficulties and emphases in the study of Lidar data post-processing, and also the primary problem needed to be solved. Least squares adjustment is used to fit block terrain in traditional moving curved fitting filtering method, but this method is sensitive to outliers. Aiming at solving this disadvantage, robust estimation theory is introduced to fit block terrain more reasonably, and self-adaption threshold is set to distinguish between ground and non-ground points automatically. The test data provided by International Society for Photogrammetry and Remote Sensing (ISPRS) are adopted for experiment. Compared with 8 classical filtering methods, experimental results prove that, robust estimation can provide more reasonable fitting curve, which means that the proposed method is practical with reliable filtering results and has strong adaptability to various terrains..
Laser & Optoelectronics Progress
- Publication Date: Oct. 11, 2015
- Vol. 52, Issue 12, 122801 (2015)
A Combination Method of Wavelet Transform and Generalized Gaussian Model for Airborne Laser Scanning Waveform Decomposition
Duan Yihao, Zhang Aiwu, Liu Zhao, Li Tao, Xiao Tao, and Ye Qiuhong
In view of the problem that overlapping pulses in small footprint full waveform airborne laser scanning waveform data are difficult to parse and the actual measurement wave data usually shows the broadening or peak form. A combination method of wavelet transform and generalized Gaussian model (WT-GGM) is proposed to reIn view of the problem that overlapping pulses in small footprint full waveform airborne laser scanning waveform data are difficult to parse and the actual measurement wave data usually shows the broadening or peak form. A combination method of wavelet transform and generalized Gaussian model (WT-GGM) is proposed to resolve the wave data of airborne LiDAR. The wavelet transform method with the characteristics of multi-resolution analysis shows the unique advantages in detecting the non-stationary, weak, transient and singular signals. The compare generalized Gaussian model as the waveform component modeling model can effectively dispose the broadening or peak form by adjusting its shape parameter. In order to verify the validity of the proposed algorithm, a contrast experiment of waveform analysis is carried out by using the WT-GGM method, the COG method, the GIPM method and the RGD algorithm. The results show that the wavelet transform can effectively decompose the targets within the overlapping waveform. And the number of targets detected by the WT-GGM method is roughly the same with the GIPM and RGD method, two times of the COG method..
Laser & Optoelectronics Progress
- Publication Date: Nov. 25, 2015
- Vol. 52, Issue 12, 122802 (2015)
Evaluation of Thermal Drift Error Performance of Fiber Optic Gyroscope
Zhang Yonggang, Li Shuting, Gao Zhongxing, and Chen Xiaowei
In practical applications, the effect of the temperature changing rate on the thermal drift error of a fiber optic gyroscope (FOG) can not be ignored fiber optic gyroscope (FOG) due to temperature variation. Effect of temperature variation on thermal drift error of FOG in theory is analyzed. Then a temperature cycling In practical applications, the effect of the temperature changing rate on the thermal drift error of a fiber optic gyroscope (FOG) can not be ignored fiber optic gyroscope (FOG) due to temperature variation. Effect of temperature variation on thermal drift error of FOG in theory is analyzed. Then a temperature cycling experiment is designed to obtain the thermal drift error in seven temperature rates. Based on experimental data, a function is utilized to describe the relationship between temperature changing rate and thermal drift error of the FOG. With this fitting function, the thermal drift error of a FOG under any temperature changing rate will be obtained, and parameters of the function can be used to evaluate the thermal performance of a FOG..
Laser & Optoelectronics Progress
- Publication Date: Nov. 20, 2015
- Vol. 52, Issue 12, 122803 (2015)
Reviews
Progress of Study on Long Tapered Double-Clad Fiber in Fiber Laser Application
Shi Chen, Wang Xiaolin, Su Rongtao, Zhou Pu, Xu Xiaojun, and Lu Qisheng
Tapered fiber is fabricated from traditional uniformed fiber using fused conical tapering, mechanical affection, chemical corrosion and so on, whose radius is various with the length of fiber. The changing part of fiber core is called tapered area. When the tapered area is distributed in whole double-clad fiber, the fiTapered fiber is fabricated from traditional uniformed fiber using fused conical tapering, mechanical affection, chemical corrosion and so on, whose radius is various with the length of fiber. The changing part of fiber core is called tapered area. When the tapered area is distributed in whole double-clad fiber, the fiber is called a tapered double-clad fiber (T-DCF). The developing progress of tapered fiber is summarized, the advantages and basic theories of application of T-DCF in fiber laser area are described, some major experimental results of T-DCF are discussed, and the developing trend of T-DCF in fiber laser application is listed..
Laser & Optoelectronics Progress
- Publication Date: Sep. 24, 2015
- Vol. 52, Issue 12, 120001 (2015)
Development of Function Films Prepared by Pulsed Laser Deposition Technology
Cheng Yong, Lu Yimin, Guo Yanlong, Huang Guojun, Wang Shuyun, Zhu Mengzhen, Li Wei, Mi Chaowei, and Cao Haiyuan
Pulsed laser deposition technology, which is considered to be one of the best method for preparing function films, has the large development potential and broad application. It′s indicated that: mostly all the films could be prepared by pulsed laser deposition technology; most of pulsed laser depositions are carried ouPulsed laser deposition technology, which is considered to be one of the best method for preparing function films, has the large development potential and broad application. It′s indicated that: mostly all the films could be prepared by pulsed laser deposition technology; most of pulsed laser depositions are carried out by excimer laser with the wavelength of 248 nm whose photon energy is high, and most of films are prepared by single laser in the gas and heater condition; the films prepared by pulsed laser deposition are amorphous or polycrystalline, and a few of single crystal films are prepared just in the condition of very high temperature and vacuum. On the base of the characteristics of this technology, the pulsed laser deposition system with magnetic filter technology is designed and founded to supply the technology and hardware base for improving the performances of function films prepared by pulsed laser deposition..
Laser & Optoelectronics Progress
- Publication Date: Nov. 26, 2015
- Vol. 52, Issue 12, 120003 (2015)
Research Progress on Improving the High-Temperature Oxidation Resistance of MCrAlY Coatings
Zhou Shengfeng, Liu Jia, Xiong Zheng, Dai Xiaoqin, Li Linghua, Zhang Zezhong, and Gu Menghao
MCrAlY coatings prepared by conventional methods have polycrystalline structure, micropores and cracks. The high-temperature oxidation resistance of MCrAlY coatings needs to be improved. Many measurements have been put forward by domestic and foreign researchers to improve their high-temperature oxidation resistance. TMCrAlY coatings prepared by conventional methods have polycrystalline structure, micropores and cracks. The high-temperature oxidation resistance of MCrAlY coatings needs to be improved. Many measurements have been put forward by domestic and foreign researchers to improve their high-temperature oxidation resistance. These methods are reviewed and the related problems are also analyzed. Moreover, the method on cryomilling inducing the columnar growth of MCrAlY coatings by laser-induction hybrid cladding (LIHRC) is put forward. NiCr powder (or NiCr powder, Co powder), Al powder and Y2O3 powder are treated by mechanical alloying in high-energy milling apparatus to obtain the cladding powder consisting of γ-Ni/γ′-Ni3Al with large amounts of internal defects. The cryomilled MCrAlY powder presents the polygonal morphology. Preheating the substrate by induction heater is combined with laser cladding simultaneously. This method can not only obtain the crack-free MCrAlY coatings, but also induce the columnar growth in MCrAlY coatings. The high-temperature oxidation resistance of MCrAlY coating is improved significantly..
Laser & Optoelectronics Progress
- Publication Date: Nov. 26, 2015
- Vol. 52, Issue 12, 120004 (2015)
Scattering
Analysis and Suppression of Stray Radiation of Shortwave Infrared Imaging System
Ren Guodong, Zhang Liang, Lan Weihua, Zhao Yan, and Pan Xiaodong
According to the problem that stray radiation exists in the process of imaging at shortwave infrared lens. The stray radiation analysis and suppresses research of lens are carried on. By imaging experiment, the stray radiation phenomena of lens is analyzed preliminarily. The analysis model of shortwave infrared lens isAccording to the problem that stray radiation exists in the process of imaging at shortwave infrared lens. The stray radiation analysis and suppresses research of lens are carried on. By imaging experiment, the stray radiation phenomena of lens is analyzed preliminarily. The analysis model of shortwave infrared lens is established using simulation software Tracepro, the point source transmittance (PST) of system is obtained, rays tracing is conducted according to the experimental phenomenon, and the possible path of stray radiation is found out. Stray radiation is restrained by increase lens hood, modify the structure and adding extinction stray light coatings. The measured PST after taking the proposed methods can prove the effectiveness and trustiness of these methods, and reach the goal of suppress stray radiation of the lens and improve image quality..
Laser & Optoelectronics Progress
- Publication Date: Nov. 07, 2015
- Vol. 52, Issue 12, 122901 (2015)
Spectroscopy
A Methane Gas Sensor System Based on Tunable Diode Laser Absorption Spectroscopy
Zeng Pan, Ni Yi, Gao Pan, and Liu Sen
A methane gas sensor system based on tunable diode laser absorption spectroscopy is designed, mainly aiming at wide temperature range, full concentration, high precision of real-time testing instruments. The feature of high sensitivity is accomplished by choosing a 1653.7 nm narrow-linewidth distributed-feedback laser A methane gas sensor system based on tunable diode laser absorption spectroscopy is designed, mainly aiming at wide temperature range, full concentration, high precision of real-time testing instruments. The feature of high sensitivity is accomplished by choosing a 1653.7 nm narrow-linewidth distributed-feedback laser source, adopting the multiple reflection chambers and combining wavelength tuning with full digital lock-in amplifier. Using the least squares method, the second harmonic signal data under different temperature and concentrations are fitted. The detection accuracy is improved by taking background subtraction and temperature compensation methods. Experimentally, the low-power on-line system can test the methane gas in full-scope concentration range. It has response time of less than 10 s, and its testing error is lower than ±0.02% under the concentration of 0~1%, and lower than ±2% of actual value under the concentration of 1%~100%. Through the long time stability test and high-low temperature test, high reliability in a wide temperature range (0 ℃~40 ℃) of the system is verified, and the system meets the coal mine test standards and provides guarantee for prevention and control of methane gas outburst hazards..
Laser & Optoelectronics Progress
- Publication Date: Nov. 03, 2015
- Vol. 52, Issue 12, 123001 (2015)
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