Contents
2013
Volume: 33 Issue 10
49 Article(s)
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Atmospheric Optics and Oceanic Optics
Study on Remote Sensing of Water Vapor Column Concentration in the Atmosphere by Direct-Sun Infrared Absorption Spectroscopy
Cheng Siyang, Gao Minguang, Xu Liang, Li Sheng, Jin Ling, Tong Jingjing, Liu Jianguo, and Liu Wenqing
A remote sensing system of ground-based Fourier transform infrared spectrometer is developed, automatically recording solar near infrared absorption spectra on sunny day. The real-time whole atmospheric transmittance spectrum is obtained through the recorded single spectrum. Based on the optimization method, total coluA remote sensing system of ground-based Fourier transform infrared spectrometer is developed, automatically recording solar near infrared absorption spectra on sunny day. The real-time whole atmospheric transmittance spectrum is obtained through the recorded single spectrum. Based on the optimization method, total column concentrations of water vapor in the atmosphere are retrieved from the transmittance spectra on the observation site between October 17, 2011 and March 6, 2013. Total column concentrations of water vapor, obtained by the ground-based remote sensing technology with high temporal resolution, are compared with the ones by solar radiometer. They agree very well with each other and the correlation coefficient is 92%. Total column concentrations of water vapor change a lot during a day in the measurement site area, and there is no obvious periodicity. The characteristics of diurnal variation are complex and associated with many factors. Owing to factors such as atmospheric circulation and seasonal variation of temperature, total column concentrations of water vapor show the characteristic of obvious seasonal cycle in the measurement site area, which is significantly higher in summer than in winter. These results are significant to the research and application of water vapor detection and analysis method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1001001 (2013)
Atomic and Molecular Physics
Experimental Measurements and Accurate Simulation of the Optical Thickness of the Cesium Atom Vapor
Guo Miaojun, Wu Jinze, Huang Jingbo, Wang Hongli, Zhou Haitao, Gao Jiangrui, and Zhang Junxiang
The experimental measurements of the optical thickness of the cesium atom vapor interacting with the lights of different intensities and polarizations at different energy levels and temperatures are demonstrated. The rate equations of each Zeeman sublevels are established theoretically and the numerical solution of timThe experimental measurements of the optical thickness of the cesium atom vapor interacting with the lights of different intensities and polarizations at different energy levels and temperatures are demonstrated. The rate equations of each Zeeman sublevels are established theoretically and the numerical solution of time-dependent absorption coefficients is obtained by solving the rate equations with Runge-Kutta methods. The average absorption coefficients at resonant frequency can be calculated by numerical integration because of the effects of the thermal motion of atoms and beam width. The fitting of transmission spectrum of the cesium vapor cell is carried out accurately by using the Beer′s law and then the accurate values of the optical thickness of the cesium atom vapor are obtained finally. Theoretical analysis and experimental result show that higher temperatures lead to larger optical thickness while higher optical intensities result in smaller optical thickness..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1002001 (2013)
Diffraction and Gratings
Generation of Polarization-Adjustable Cylindrical Vector Beams Based on Vortex Phase Modulation and Interference
Wang Yifan, Kuang Cuifang, Gu Zhaotai, Li Shuai, and Liu Xu
Cylindrical vector beam can be widely used in the fields of photoetching, optical micro processing, optical tweezers and optical superresolution. To overcome the existing problems of the complexity of its setup and the unadjustable polarization, generation of cylindrical vector beam with adjustable polarization based oCylindrical vector beam can be widely used in the fields of photoetching, optical micro processing, optical tweezers and optical superresolution. To overcome the existing problems of the complexity of its setup and the unadjustable polarization, generation of cylindrical vector beam with adjustable polarization based on vortex phase modulation and interference is studied both theoretically and experimentally. Feasibility of our scheme is proved in theory, and intensity distributions of radially polarized beam and azimuthally polarized beam are simulated. Meanwhile, related experiments are conducted to prove the correctness of the theory. By rotating the relative angle between two vortex phase plates, the obtained radially polarized beam can be changed into azimuthally polarized one. Experimental results are agree with the theoretical analyses..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1005001 (2013)
Broadband and High Resolution Spectral Measurement Technique for Pulse Compression Gratings
He Kai, Liu Shijie, Hou Yongqiang, Li Xu, Jin Yunxia, and Yi Kui
Pulse compression gratings based on multilayer dielectric film or metal multilayer dielectric film usually work around the Littrow angle with high diffraction efficiency and broad diffraction band. There is a large requirement to have high resolution and accurate measurement on the grating diffraction spectrum in the pPulse compression gratings based on multilayer dielectric film or metal multilayer dielectric film usually work around the Littrow angle with high diffraction efficiency and broad diffraction band. There is a large requirement to have high resolution and accurate measurement on the grating diffraction spectrum in the purpose of optimizing the fabrication process. Based on the double light paths system, an optical characterization method and the corresponding setup with high spectral resolution for broadband high diffraction efficiency pulse compression gratings are demonstrated. The method to eliminate the influence of the background and the light source fluctuation is discussed in detail. Two practical problems are perfectly settled, including the large spot size of diffracted light which is not completely collected by optical detector and the detector blocking of the incident light near the Littrow angle. The setup can measure the reflection and transmission diffractive spectra for each diffractive order of broadband pulse compression gratings, as well as the angular spectrum with fixed wavelength. The setup can measure the grating diffractive spectrum with resolution of 1 nm and the grating angular spectrum with resolution of 0.2° at present. The optical spectrum and angular spectrum of pulse compression grating samples are measured on the established measurement setup. Diffraction efficiencies greater than 90% in the wavelength range of 770~870 nm are obtained with measurement error no more than 2.2% and average relative deviation no more than 1.0%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1005002 (2013)
Fiber Optics and Optical Communications
Influence of Trench Parameters on the Characteristic of Trench-Assisted Multi-Core Fiber
Zheng Siwen, Ren Guobin, Lin Zhen, Jian Wei, and Jian Shuisheng
The effects of different trench parameters on the crosstalk and the mode area in the trench-assisted multi-core fiber are investigated systematically. Simulations suggest that low crosstalk and/or large mode area can be achieved by adjusting the trench parameters. Furthermore, the effects of different trench parametersThe effects of different trench parameters on the crosstalk and the mode area in the trench-assisted multi-core fiber are investigated systematically. Simulations suggest that low crosstalk and/or large mode area can be achieved by adjusting the trench parameters. Furthermore, the effects of different trench parameters on the dispersion characteristic are discussed, and the dispersion characteristics of the structures are verified experimentally. These characteristics suggest that the large-mode-area low-crosstalk trench-assisted multi-core fiber can be an important potential candidate for practical applications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1006001 (2013)
Inter-Carrier Interference Suppression Algorithm for OFDM-PON Systems Based on Pseudo-Symmetrical Training Sequences
Lu Zhenlong, Wang Junhua, Sun Yanzan, Wang Min, and Fang Yong
The inter-carrier interference (ICI) in passive optical network (PON) systems based on orthogonal frequency division multiplexing (OFDM) technology is resulted in seriously by kinds of fiber nonlinear factors. An algorithm based on the pseudo-symmetrical training (PST) sequences is proposed to solve the problem; two ToThe inter-carrier interference (ICI) in passive optical network (PON) systems based on orthogonal frequency division multiplexing (OFDM) technology is resulted in seriously by kinds of fiber nonlinear factors. An algorithm based on the pseudo-symmetrical training (PST) sequences is proposed to solve the problem; two Toeplitz sub-systems which are transformed from the mentioned problem are to be solved. The input of the second sub-system is achieved by pre-processing the first sub-system. As a result, the output of the second sub-system can be achieved based on least square (LS) criterion. At last, the suppression of ICI can be achieved. The characteristic of PST sequences and fast Fourier transform (FFT) are introduced into the proposed algorithm refraining from traditional high order inversion. As a result, the real-time performance of the calculation is improved. Simulation results show that the proposed algorithm for OFDM-PON systems can not only suppress ICI, but also improve the real-time performance dramatically..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1006002 (2013)
Affect Analysis of Receiving Aperture on Bit-Error Rate Performance in Free Space Optical Communication Systems under Different Visibilities
Wu Xiaojun, Wang Hongxing, and Liu Min
Visibility is a crucial factor of affecting link performance in free space optical (FSO) communication. The bit-error rate (BER) model which does not consider the effect of turbulence is built. On this basis, the affect of receiving aperture on BER under different visibilities is studied by combing the actual visibilitVisibility is a crucial factor of affecting link performance in free space optical (FSO) communication. The bit-error rate (BER) model which does not consider the effect of turbulence is built. On this basis, the affect of receiving aperture on BER under different visibilities is studied by combing the actual visibility data and using the method of simulation. The results show that there are many differences between receiving aperture and BER under different visibilities. If the visibility is high, the BER is much lower, and the performance of system is better. The improvement of the receiving aperture on BER is obvious. At the same time, combining the requirement for BER in engineering practice, the choice of appropriate receiving aperture is discussed under different visibilities, which provides valuable theoretical reference for building the FSO communication link..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1006003 (2013)
Research of the Influence of Bandwidth of Light Source on the Optical Correlator Based on Fiber Dispersion
Qin Fengjie, Tan Zhongwei, and Ning Tigang
With the increasing of high-bit-rates transmission over optical fiber and especially with the appearance of packet-switched networks, optical correlation detection technology will have many applications in future telecommunication systems including IP router. Beginning with the basic theory of the optical correlator baWith the increasing of high-bit-rates transmission over optical fiber and especially with the appearance of packet-switched networks, optical correlation detection technology will have many applications in future telecommunication systems including IP router. Beginning with the basic theory of the optical correlator based on fiber dispersion, the influence of the bandwidths of different light sources on the performance of optical correlator is compared by using theoretical analysis and numerical simulation, and phase noise converted into intensity noise by dispersion is analyzed. So it concludes that intensity noise is related with the light source bandwidth, and the signal-to-noise ratio of the optical correlation can be changed when using light source with different bandwidths. According to the simulation results, it is demonstrated that optical correlator based on incoherent light source can recognize 8-bit and 16-bit patterns in 10-Gb/s data streams, but correlation detection of 32-bit patterns can only use coherent light source. Besides, potential application of optical correlator based on incoherent light in the detection of the analog signal is discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1006004 (2013)
Sensing Characteristics of Mach-Zehnder Interferometer Based on the Fused Tapered Photonic Crystal Fiber Sensor
Ji Yushen, Fu Guangwei, Fu Xinghu, Shen Yuan, and Bi Weihong
Based on the fused tapered photonic crystal fiber (PCF), a Mach-Zehnder interferometer is proposed. The both ends of PCF is joined in a splice with a single-mode fiber and the interference fringe contrast of the transmission spectra is 2.23 dB. The transmission spectra of sodium chloride solutions with different mass cBased on the fused tapered photonic crystal fiber (PCF), a Mach-Zehnder interferometer is proposed. The both ends of PCF is joined in a splice with a single-mode fiber and the interference fringe contrast of the transmission spectra is 2.23 dB. The transmission spectra of sodium chloride solutions with different mass concentrations are obtained. The corresponding relationships between the transmission spectra and external refractive index are analyzed. The experimental results show that the refractive index sensitivity of the sensor is 210.075 nm/RIU in the index range of 1.333~1.349, by measuring different mass concentrations of the sodium chloride solutions. In the temperature range of 20 ℃~70 ℃, the temperature sensitivity is about 0.0018 nm/℃ . This sensor is able to overcome the problem of cross sensitivity of temperature in the measurement..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1006005 (2013)
Research on Transmission Mechanism and Characteristics of Hollow-Core Photonic Bandgap Fiber Gratings
Qi Yuefeng, Zhou Liying, Bi Weihong, and Wang Wei
The transmission mechanism of hollow-core photonic bandgap fiber gratings is studied based on finite element method and coupled local-mode theory. The model of holes collapse is built, the distributions of effective refractive indexes and mode coupling coefficients are calculated in the structural change region, and thThe transmission mechanism of hollow-core photonic bandgap fiber gratings is studied based on finite element method and coupled local-mode theory. The model of holes collapse is built, the distributions of effective refractive indexes and mode coupling coefficients are calculated in the structural change region, and the transmission spectrum is obtained by the coupling between fiber core fudmental mode (LP01) and cladding mode (LP11). Furthmore, the impacts of the fiber and gratings structure parameters involving in the air hole diameter, air hole spacing, grating period, the number of periods, the depth of cladding collapse and the collapse way on resonant peaks are studied. The results indicate that the resonant wavelength shifts to short wavelength direction varying with the increase of air hole diameters and the gratings period, the decrease of air hole spacing and collapse depth. The resonant wavelength shows no obvious shift with the increase of the number of periods. Otherwise, the resonant wavelength shifts towards short wavelength direction where the fiber is heated by single-side collapse comparing with symmetric collapse..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1006006 (2013)
Fourier Optics and Signal Processing
Interferogram Filtering Method Based on Empirical Mode Decomposition
Jing Juanjuan, Xiangli Bin, Li Ran, and Shi Dalian
Interferogram filtering is a key technique in the process of spectral recovery of imaging Fourier transform spectrometer. Differential filtering and polynomial filtering are usually used, but differential filtering cannot filter the noise completely, and polynomial filtering, which needs the noise type when filtering, Interferogram filtering is a key technique in the process of spectral recovery of imaging Fourier transform spectrometer. Differential filtering and polynomial filtering are usually used, but differential filtering cannot filter the noise completely, and polynomial filtering, which needs the noise type when filtering, produces big bias at both ends of the interferograms. Empirical mode decomposition (EMD), a new signal processing method in linearity and stationary spectral analysis, is now widely used in many aspects. EMD technique is applied to interferogram filtering. It can avoid the disadvantages of differential filtering and polynomial filtering, and it is more reasonable to extract the background noise. The data acquired in the laboratory are used to analyze the precision of different filtering methods. The result indicates that the precisions of differential filtering, polynomial filtering and EMD are 0.0079, 0.0073, 0.0068, respectively. EMD is the optimum filtering method, followed by the polynomial filtering and differential filtering..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1007001 (2013)
Geometric Optics
Performance Analysis of Fixed Mirror Solar Concentrator Mirror Field
Zhou Xizheng, Ma Chunyuan, Wang Junqi, and Zhang Zhen
The fixed linear mirror solar concentrator and its working principle are introduced. It is necessary to culate solar beam radiation on each of tilted mirror for the design of solar collector system. Fixed mirror solar concentrator (FMSC) is an approximation which treats smooth linear optical reflector as broken into seThe fixed linear mirror solar concentrator and its working principle are introduced. It is necessary to culate solar beam radiation on each of tilted mirror for the design of solar collector system. Fixed mirror solar concentrator (FMSC) is an approximation which treats smooth linear optical reflector as broken into segments. The incidence angle and illuminate area of every mirror consequentially vary throughout the year, which makes the calculation of the beam radiation relatively complex. The equation of incidence angle, illuminate area and geometric concentration ratio are obtained by vector analysis. And the instantaneous solar beam radiation of whole mirror field is computed. Finally, the cumulated irradiation of overall system is obtained during the available work. Furthermore, two kinds of concentrator are compared, including installation on the south facing with slope of latitude angle and adjustment of a tilt angle one year (spring and summer use). Adjusting slope angle once a year, radiation from concentrator system with open width of 1800 mm increases by 6.53%, with an increment of 65.78 GJ/m..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1008001 (2013)
Holography
Surface Profile Measurement of Microstructures Based on Dual-Wavelength Digital Microscopic Image-Plane Holography
Zeng Yanan, Wang Fei, Lei Hai, Hu Xiaodong, and Hu Xiaotang
To enlarge the effective field of view, speed up the response time and reduce the noise of the real-time surface profile measurement of microstructures by traditional dual-wavelength digital holographic microscopy, a technique named dual-wavelength digital microscopic image-plane holography is developed. It is a combinTo enlarge the effective field of view, speed up the response time and reduce the noise of the real-time surface profile measurement of microstructures by traditional dual-wavelength digital holographic microscopy, a technique named dual-wavelength digital microscopic image-plane holography is developed. It is a combination of digital microscopic image-plane holography and the traditional dual-wavelength digital holographic microscopy. The phase and amplitude can be directly extracted from the hologram plane to yield the surface profile of microstructure without calculation of the diffraction after recording the image-plane hologram. A microstep with several micrometers in height is tested by the dual-wavelength digital image-plane holographic microscope, the traditional digital holographic microscope and the stylus profilometer. As can be seen from the comparison of the testing results, the dual-wavelength digital microscopic image-plane holography is feasible with the characteristics of single-exposure, completely full-field, short response time and low noises. It is especially suitable for the real-time surface profile measurement of microstructures with step height in the micrometer range..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1009001 (2013)
Synchronous Multi-Channel Phase-Shifting Digital Holographic Technology
Zhang Jing, Ye Yutang, Xie Yu, Liu Juanxiu, Liu Lin, Chang Yongxin, and Luo Ying
A new synchronous multi-channel phase-shifting holography, which is suitable for dynamic imaging of three-dimensional (3D) objects, is proposed by analyzing the theory of phase-shifting digital holography. The reference beam, which has continuous 90-degree phase delay on the free space, interferes with optical field ofA new synchronous multi-channel phase-shifting holography, which is suitable for dynamic imaging of three-dimensional (3D) objects, is proposed by analyzing the theory of phase-shifting digital holography. The reference beam, which has continuous 90-degree phase delay on the free space, interferes with optical field of laser diffraction through object. Multi-frame holograms are taken by using the balanced detector system which is comprised of four cameras. The information of 3D object is reconstructed based on Fresnel and Fourier optical principles. Simulation and experimental results show that single-shot phase-shifting digital holography has been achieved, synchronous multi-channel can be used for real-time measurement of dynamic objects, a large number of simultaneous multi-frame images improve the quality of the image..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1009002 (2013)
Imaging Systems
Sparse Angular Differential Phase-Contrast Computed Tomography Reconstruction Using Bregman Operator Splitting Algorithm
Li Jing, Li Mengjie, and Sun Yi
Phase-contrast computed tomography (CT), different from traditional absorption-contrast tomography, is a novel X-ray inspection method and has been widely used for it′s high sensitivity, high resolution and better reconstructions for soft tissues. However, phase-contrat CT usually leads to unacceptably long exposure tiPhase-contrast computed tomography (CT), different from traditional absorption-contrast tomography, is a novel X-ray inspection method and has been widely used for it′s high sensitivity, high resolution and better reconstructions for soft tissues. However, phase-contrat CT usually leads to unacceptably long exposure time and huge X-ray doses. Sparse angular algorithms show significant advantage over in reducing the X-ray doses. Thus, the study of sparse angular differential phase-contrast CT (DPC-CT) is particularly meaningful. After analyzing the characteristics of the DPC-CT, the Bregman operator splitting (BOS) algorithm is introduced into DPC-CT reconstruction and an alternating iteration algorithm for sparse angular DPC-CT is proposed. The numerical simulation and experiment results show that the proposed algorithm can obtain higher reconstruction quality in sparse angular condition..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1011001 (2013)
Improving Sensitivity of Fluorescence Molecular Tomography by Region-Based Diffuse Optical Tomography
Wu Linhui, Zhao Huijuan, Yi Xi, Zhang Wei, and Gao Feng
In view of low imaging resolution and quantitative accuracy in fluorescence molecular tomography (FMT) which are caused by the assumption of homogeneous optical structural background, and considering that the “coarse-grain” diffuse optical tomography (DOT) methodology based on region-labeling (region-based DOT) presentIn view of low imaging resolution and quantitative accuracy in fluorescence molecular tomography (FMT) which are caused by the assumption of homogeneous optical structural background, and considering that the “coarse-grain” diffuse optical tomography (DOT) methodology based on region-labeling (region-based DOT) presents a promising tool of in vivo reconstructing background optical structure with the aid of anatomical a priori, an approach of region-based DOT guided FMT reconstruction algorithm under continuous-wave mode is developed for improving sensitivity of FMT. Numerical simulations are conducted on a region-labeled three-dimensional (3D) digital mouse atlas. The reconstructed fluorescent yield image with optical structural a priori information provided by region-based DOT algorithm is compared with the results with accurate optical structural background and hypothetical homogeneous background, respectively, to investigate the performance of this method. Physical experiments on a phantom are also conducted to assess this methodology. Our simulated and experimental reconstruction results indicate that this region-based DOT guided FMT approach can significantly improve the sensitivity of FMT, as well as its imaging resolution and quantitative accuracy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1011002 (2013)
Fast Automatic Exposure Approach for Color Digital Camera
Guo Huinan, Cao Jianzhong, Zhou Zuofeng, Liao Jiawen, and Liu Qing
Exposure accuracy of color digital camera directly affects the performance of color image and the sensory effects of human visual. An automatic exposure method of digital camera based on the color perceiving properties of human visual system, is proposed. A novel kind of exposure estimation function is also establishedExposure accuracy of color digital camera directly affects the performance of color image and the sensory effects of human visual. An automatic exposure method of digital camera based on the color perceiving properties of human visual system, is proposed. A novel kind of exposure estimation function is also established through objective evaluating the sharpness, color saturation and brightness of input images. According to the statistical theory and empirical formulas, the functional relationship between the exposure estimation values and exposure step increment is calibrated and the exposure increment function is established as well. For different brightness properties of current frame, using the exposure increment function, the ideal exposure value of next frame in real time is calculated. A large number of experimental results show that the proposed method for different scenes and different lighting conditions always has a good performance in adjusting exposure value of the captured image. Meanwhile, the algorithm has good robustness which can achieve adjustment for input frames in short time..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1011003 (2013)
Instrumentation, Measurement and Metrology
Error Analysis for the Non-Contact Measuring System of Pointing Mirror
Wang Yang, Yan Changxiang, Zhang Da, Wang Yiqun, Gao Zhiliang, and Liu Dongbin
In order to measure the motion characteristics of the pointing mirror of the hyperspectral imager, a non-contact measuring system of the pointing mirror is designed. Before processing and aligning, it is extremely necessary to make an error distribution scheme according to the system′s uncertainty which is impacted by In order to measure the motion characteristics of the pointing mirror of the hyperspectral imager, a non-contact measuring system of the pointing mirror is designed. Before processing and aligning, it is extremely necessary to make an error distribution scheme according to the system′s uncertainty which is impacted by various error sources in processing and aligning. The mathematical model with errors of processing and aligning is established via the homogeneous coordinate. The curve of rotation angle and spot position is obtained by curve fitting. The error distribution scheme is determined based on the error of relative position measurement. The error distribution scheme ensures that the measurement uncertainty is 2″ and the resolution is 0.5″ in 11° measurement range. The error distribution scheme reduces the accuracy requirements of processing and aligning and validates the feasibility of the system design..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1012001 (2013)
Study on Calibration Technology of High-Precision Flexible Coordinate Measurement System
Liu Changjie, Ma Shuang, Guo Yin, Liu Miao, Zhu Jigui, and Ye Shenghua
To solve the problem of the traditional flexible measuring system due to the imperfect robot module and the changing parameters, a calibration technology of high-precision flexible coordinate measurement system is proposed. Binocular stereo vision method is employed to construct the global measurement unit. In order toTo solve the problem of the traditional flexible measuring system due to the imperfect robot module and the changing parameters, a calibration technology of high-precision flexible coordinate measurement system is proposed. Binocular stereo vision method is employed to construct the global measurement unit. In order to ensure the accuracy, a camera calibration method which is based on space grid control field, and a method of the global space precise positioning are proposed. The pose transformation of the robot in space can be accurately measured by the two global cameras in the scene, through measuring the controlling points on the stereovision sensor. The experimental results verify that the error of the global camera is less than ±0.1 mm, and the error of the whole measurement system is smaller than ±0.15 mm. The measurement can satisfy the precision requirement of the system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1012002 (2013)
Measurement and Reconstruction for Large Aero-Optics Wavefront Distortion Field
Zhao Tao, Zhang Zhengyu, Wang Shuiliang, and Zhu Long
Measurement and calibration of aero-optics effects are necessary for all kinds of optical systems onboard high-speed aircraft, such as detection systems of photoelectric imaging, directed energy systems and optical communication system, etc. Therefore, a method of measurement and reconstruction for wavefront distortionMeasurement and calibration of aero-optics effects are necessary for all kinds of optical systems onboard high-speed aircraft, such as detection systems of photoelectric imaging, directed energy systems and optical communication system, etc. Therefore, a method of measurement and reconstruction for wavefront distortion field is presented, which gets the optical path difference (OPD) through measuring deviation displacement field induced by the beam from center of camera to a mark point passing through flow field, and the relationship between the order of Zernike polynomial and reconstruction precision is also investigated. The experiments of a trans-aerosphere vehicle model in 2 m supersonic wind tunnel testing have demonstrated that the proposed method can be used to measure large wavefront distortion field, and structures of wavefront distortion generated by oblique shock waves of the vehicle′s head and wing are correct. The optical devices of this method are simple, and no expensive coherent source is needed. It is a new way to measure and calibrate aero-optics effects..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1012003 (2013)
Study of the Measurement Range of S-Transform Profilometry
Zhong Min, Chen Wenjing, Su Xianyu, and Zheng Yi
S-transform, combining the advantages of both the windowed Fourier transform and the wavelet transform, is suitable for the demodulation of non-stationary signal such as the deformed fringe pattern. The fringe patterns analyzed by S-transform are discrete in application. During the calculation of the S-stransform coeffS-transform, combining the advantages of both the windowed Fourier transform and the wavelet transform, is suitable for the demodulation of non-stationary signal such as the deformed fringe pattern. The fringe patterns analyzed by S-transform are discrete in application. During the calculation of the S-stransform coefficients, the Fourier spectrum of the signal is translated, which means that the frequency information of the adjacent island is used. The frequency overlapping caused by sampling, nonlinearity or height variation of the measured object affects the three-dimensional reconstruction result. The effects from the above factors in calculating S-transform coefficients are exhaustively studied from the point of view of the frequency analysis. The frequency-domain description and the measurement range of S-transform coefficients of digital signal are deduced when the nonlinearity from both the projector and CCD exists. The sampling condition and the structure condition are given as well. Both computer simulation and experimental results verify the analysis..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1012004 (2013)
Integrated Optics
Study on a Tunable Radio Frequency Filter Based on Integrated Optical Waveguide
Zou Pin, Han Xiuyou, Wang Yu, Wang Linghua, Gu Yiying, Wang Jinyan, Jian Xigao, and Zhao Mingshan
A new tunable microwave photonic filter combining optical waveguide micro-ring resonator and Mach-Zehnder interferometer (MZI) is proposed to realize single sideband filtering. The influences of the filter structural parameters, such as coupling coefficient κr, round-trip loss γ1 and additional phase shift Δφ1, etc., oA new tunable microwave photonic filter combining optical waveguide micro-ring resonator and Mach-Zehnder interferometer (MZI) is proposed to realize single sideband filtering. The influences of the filter structural parameters, such as coupling coefficient κr, round-trip loss γ1 and additional phase shift Δφ1, etc., on the filtering response are investigated. The result shows that there is a tradeoff between the rectangle shape and extinction ratio. According to the polymer polysilsesquioxane-liquid (PSQ-L) waveguide, a microwave photonic filter with rectangle shape factor of 0.8 and extinction ratio of 32 dB is designed, and the tunable radio frequency single sideband filtering from 8 GHz to 69 GHz can be achieved with the thermal-optic phase shifters..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1013001 (2013)
Geometrical Optimization of Single-Mode Rib Waveguides with Large Cross Section
Yan Chaojun, Peng Wenbiao, and Qin Qin
If the geometrical structure of a rib waveguide with large cross section meets the conditions of single mode, the waveguide device does not necessarily work in the best status. The interference of leaky modes often cannot be ignored. The scalar finite difference beam propagation method is used to calculate the attenuatIf the geometrical structure of a rib waveguide with large cross section meets the conditions of single mode, the waveguide device does not necessarily work in the best status. The interference of leaky modes often cannot be ignored. The scalar finite difference beam propagation method is used to calculate the attenuation degree of leaky modes supported by the single-mode rib waveguides with different geometric dimensions. When the attenuation is the largest, the geometrical structure of rib waveguide is the most optimal. The single-mode condition is still satisfied after the optimization, but the attenuation of leaky modes is very large and the interference to the main mode is ignored. For a typical single-mode rib waveguide, whose width of rib is 2 μm and ratio of rib height to total height is fixed at 0.45, when the total height as variable parameter ranges from 5.4 μm to 1.3 μm, the optimized total height is 2.25 μm after the calculation of attenuation of leaky modes with different geometric dimensionings..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1013002 (2013)
Lasers and Laser Optics
Frequency Stabilization Laser Based on Non-Planar Ring Oscillator
Feng Tao, Zhang Xuejie, Ren Zhiyuan, Sun Mingying, and Zhu Jianqiang
A tunable single frequency non-planar ring oscillator laser is studied. The output power of the 1064 nm single frequency laser is 1.254 W and the slope efficiency is 51.5%. The power stability is ±0.8% within 1 h. The beam qualities of two orientations are measured, which shows the beam quality factors are M2x=1.1A tunable single frequency non-planar ring oscillator laser is studied. The output power of the 1064 nm single frequency laser is 1.254 W and the slope efficiency is 51.5%. The power stability is ±0.8% within 1 h. The beam qualities of two orientations are measured, which shows the beam quality factors are M2x=1.16 and M2y=1.05, respectively. The laser linewidth is less than 2 kHz measured by beat frequency measurement method. Besides, the frequency tuning of the single frequency laser is also studied by adjusting the temperature of the crystal. The maximum tuning range is about 18 GHz with a tuning coefficient of -2.9 GHz/℃. Meanwhile, the short-term frequency stability is obtained by self-beat-frequency method. The results show that the short-term frequency stability is 4.7×10-12 within 100 ms integral time..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1014001 (2013)
Propagation Characteristics of Gaussian Pulsed Beams with First-Order Spatio-Temporal Couplings
Zeng Shuguang, Song Laizhong, Wang Fei, Liu Yan, and He Huiling
The propagation characteristics of Gaussian pulsed beams with first-order spatio-temporal coupling (FSTC) are investigated by means of Collins formula, and the analytical expression for the FSTC beam on the output plane is derived. The rotation angle of equiphase surface is defined to estimate the severity of phase couThe propagation characteristics of Gaussian pulsed beams with first-order spatio-temporal coupling (FSTC) are investigated by means of Collins formula, and the analytical expression for the FSTC beam on the output plane is derived. The rotation angle of equiphase surface is defined to estimate the severity of phase couplings. The correlation coefficient and the rotation angle of equiphase surface are analyzed with the variation of propagation distance. The intensity distribution and phase distribution for different propagation distances are simulated. It is found that after passing a distance in the free space, the FSTC beam keeps the form, but the severity of spatio-temporal couplings, the intensity distribution and phase distribution of the FSTC beam vary with the propagation distance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1014002 (2013)
Narrow Linewidth Single Longitudinal Mode Brillouin Fiber Laser Based on Feedback Fiber Loop
Liu Yi, Yu Jinlong, Wang Wenrui, Pan Honggang, and Yang Enze
A novel narrow linewidth single longitudinal mode (SLM) Brillouin fiber laser (BFL) based on the feedback fiber loop (FFL) is proposed. The main single pass ring is constructed by an optical circulator and a 50 m single mode fiber (SMF) whose length is extended from 10 m of traditional BFL to 50 m used as laser gain meA novel narrow linewidth single longitudinal mode (SLM) Brillouin fiber laser (BFL) based on the feedback fiber loop (FFL) is proposed. The main single pass ring is constructed by an optical circulator and a 50 m single mode fiber (SMF) whose length is extended from 10 m of traditional BFL to 50 m used as laser gain medium. In order to guarantee the SLM operation, the FFL is configured with a 10 m SMF of traditional BFL. By theoretical analysis, threshold and linewidth of FFL-based BFL are better than those of traditional SLM BFL. In experiments, ring length is optimized by contrast with other two group different length SMFs. The system is enclosed in temperature control system so that environment disturbance is reduced. The SLM BFL with 99 mW threshold, 45 dB sidemode suppression and 0.8 dB power fluctuation in 1 h is obtained. 3.23 kHz linewidth is measured by delay interference method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1014003 (2013)
Machine Vision
A Novel Kernel Classification Method via Image Novelty Detection
Sun Yongxuan, Xie Zhao, and Gao Jun
The outliers in data space can benefit the boundary decision procedure in the training of classifiers. A new outlier detection method based on non-parametric affinity propagation clustering in independent subspace analysis (ISA) feature space is proposed. Similar to support vectors in support vector machine (SVM), the The outliers in data space can benefit the boundary decision procedure in the training of classifiers. A new outlier detection method based on non-parametric affinity propagation clustering in independent subspace analysis (ISA) feature space is proposed. Similar to support vectors in support vector machine (SVM), the outliers are used for the training of kernel-based classifiers. Proposed method analyzes the sample distribution in original unlabeled data space, of which the samples far from exemplars are selected as outliers, and also serves as high quality training set in both image classification and retrieval tasks. Experiments show the proposed kernel method via outliers detection outperforms state-of-art feature models. Also, the results validate the outliers detection promote classification accuracy indeed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1015001 (2013)
Improved TV-L1 Algorithm for Smooth Optical Flow
Li Xiuzhi, Yin Xiaolin, Jia Songmin, Tan Jun, and Zhao Guanrong
An optical flow method combining Gaussian convoluted data term with non-local median filter is proposed to remove noise and consequently improve the robustness and accuracy of the optical flow estimation. Robust L1 norm is employed for construction of data term, which is smoothed with Gaussian filter to suppress noise,An optical flow method combining Gaussian convoluted data term with non-local median filter is proposed to remove noise and consequently improve the robustness and accuracy of the optical flow estimation. Robust L1 norm is employed for construction of data term, which is smoothed with Gaussian filter to suppress noise, and primal-dual method is introduced to improve the estimation efficiency of variational optical flow. A global optimization strategy based on non-local median filter is used to further enhance the estimation accuracy. The coarse-to-fine pyramid technique is employed to improve the adaptability of the algorithm for large displacements estimation. The proposed method is evaluated by using both the Middlebury optical flow database images and real scene images. The experimental results show that the proposed method performs good robustness and accuracy in contrast with traditional TV-L1 model algorithms..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1015002 (2013)
Method for Fundamental Matrix Estimation Combined with Line Features
Zhou Fan, Shao Shiwei, Wu Jianhua, and Fu Zhongliang
In order to resolve the current problems of fundamental matrix estimation caused by lacking of obvious feature points, according to the epipolar geometry of the horizontal lines and vertical lines, a new method of calculating the fundamental matrix that can be combined with these two kinds of line features is proposed.In order to resolve the current problems of fundamental matrix estimation caused by lacking of obvious feature points, according to the epipolar geometry of the horizontal lines and vertical lines, a new method of calculating the fundamental matrix that can be combined with these two kinds of line features is proposed. Firstly, camera orientation elements and relative attitude are used as the elements of fundamental matrix, the equivalent relationship based on horizontal lines and vertical lines is deduced, and then the line features are made as the interior point of the RANSAC algorithm, after that the weight of each factor is determined combined with M-estimators, and finally the unified adjustment model is built. Experimental results of simulation data and real images show that the proposed approach is feasible in practice, and can reduce the dependence of intraditional method on feature points, and the introduction of the line features can improve the accuracy and stability of the calculation results to a certain extent..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1015003 (2013)
Fast Palm Vein Identification Algorithm Based on Grayscale Surface Matching
Wu Wei, Yuan Weiqi, Lin Sen, Song Hui, and Sang Haifeng
In order to improve the recognition speed with effective recognition performance of palm vein identification system, a fast palm vein identification algorithm based on grayscale surface matching is proposed. The algorithm extracts region of interest (ROI) of palm vein image firstly. Then, the ROI is equally divided intIn order to improve the recognition speed with effective recognition performance of palm vein identification system, a fast palm vein identification algorithm based on grayscale surface matching is proposed. The algorithm extracts region of interest (ROI) of palm vein image firstly. Then, the ROI is equally divided into several sub-regions. The algorithm computes average value of the grayscale of every sub-region. These average values construct an image for matching. At the stage of matching, the algorithm computes the difference between two pixels from two matching images and gets the grayscale difference surface. It calculates the variance of the grayscale difference surface and considers this variance as the distance between two feature surfaces. At last, it decides whether these two images come from the same hand or not according to the variance. A self-built palm vein database is used in the experiment. The experimental result shows that the scheme with sub-region parameter of 8 pixel×8 pixel reaches correct recognition rate (CRR) of 97.94%, with recognition time of only 0.163 ms. Compared with the traditional palm vein recognition method, the proposed method increases recognition speed with effective recognition performance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1015004 (2013)
Materials
650-nm Wavelength All-Polymer Thermo-Optical Waveguide Switch Based on Organic-Inorganic Grafting Polymethyl Methacrylate Materials
Niu Xiaoyan, Han Chao, Wang Lei, Zhang Haixin, Jiang Song, Duan Ning, Wang Fei, Chen Changming, and Zhang Daming
An novel organic-inorganic grafting polymethyl methacrylate (PMMA) material is successfully synthesized. Based on the preferable thermal stability and optical properties, the all-polymer thermo-optic(TO) waveguide switch chip at 650 nm wavelength is designed and fabricated. The chip is designed as embedded waveguide wiAn novel organic-inorganic grafting polymethyl methacrylate (PMMA) material is successfully synthesized. Based on the preferable thermal stability and optical properties, the all-polymer thermo-optic(TO) waveguide switch chip at 650 nm wavelength is designed and fabricated. The chip is designed as embedded waveguide with reversed ridge structure for single-mode propagation of the red signal light. The polymer optical fiber (POF) is used for coupling the 650nm visible light into the chip for testing. The Mach-Zehnder (M-Z) interferometer TO switch on-off time is about 600 μs. The extinction ratio is about 8.2 dB and the applied electric power as the switching power is about 22.6 mW. This device can be widely used in many fields such as high density optical integration system, visible light communication and biochemical sensing technology, etc..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1016001 (2013)
Thermal Stability of a Dually Emitting-(Ba, Sr)3MgSi2O8:Eu2+, Mn2+ Phosphor for Simultaneous Red and Blue Emission LEDs
Song Jun, Lu Qifei, Sun Liang, Li Jian, and Wang Dajian
Dependence of light intensity on temperature is investigated for a dual emission (Ba, Sr)3MgSi2O8:Eu2+, Mn2+ phosphor with a high quantum efficiency. The dual emission spectrum, which matches the photosynthetic absorption spectrum and photosynthetic effective spectrum, is composed of 660 nm-peaked red band and 430 nm-pDependence of light intensity on temperature is investigated for a dual emission (Ba, Sr)3MgSi2O8:Eu2+, Mn2+ phosphor with a high quantum efficiency. The dual emission spectrum, which matches the photosynthetic absorption spectrum and photosynthetic effective spectrum, is composed of 660 nm-peaked red band and 430 nm-peaked blue band. Thermal quenching of both red and blue band emissions is observed from 293 K to 473 K. The peak position for red exists blue-shift with temperature increasing while that for blue remains unchanged. This phenomenon is most likely associated with a multi-lattice site occupation of Mn2+ and electron-phonon interaction in the host lattice involved in an energy transfer from Eu2+ to Mn2+. The results provide further understanding of energy transfer between Eu2+ and Mn2+ and thermal quenching property of (Ba, Sr)3MgSi2O8 and reference in the application of this phosphor and the fabricated bio-lighting devices..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1016002 (2013)
Realization of Slow Light Effect for Photonic Crystal Waveguide Using Graded Eye-Shaped Scatterers
Wan Yong, Li Changhong, Yun Maojin, Guo Yue, Yang Yang, and Cui Ying
With operating wavelength λ=1550 nm, two-dimensional graded eye-shaped scatterers are applied into photonic crystal waveguide (PCW) for slow light effect in three ways: 1) getting slow light with the group index ng from 31.4 to 95.0, the low-dispersion bandwidth (Δng<10%) from 3.7 nm to 11.8 nm, the scalar product nWith operating wavelength λ=1550 nm, two-dimensional graded eye-shaped scatterers are applied into photonic crystal waveguide (PCW) for slow light effect in three ways: 1) getting slow light with the group index ng from 31.4 to 95.0, the low-dispersion bandwidth (Δng<10%) from 3.7 nm to 11.8 nm, the scalar product ng×(Δλ)/λ from 0.2268 to 0.2390, and the ultralow-dispersion bandwidth (Δng<1%) from 2.2 nm to 4.8 nm by grading the single-row eye-shaped scatterers along the longitudinal direction; 2) getting slow light with the group index ng from 31.6 to 108.2, the low-dispersion bandwidth (Δng<10%) from 4.0 nm to 13.0 nm, the scalar product ng×(Δλ)/λ from 0.2650 to 0.2792, and the ultralow-dispersion bandwidth (Δng<1%) from 2.6 nm to 6.8 nm by grading the triple-row eye-shaped scatterers periodically along the longitudinal direction; 3) getting slow light with the group index ng from 32.1 to 89.3, the low-dispersion bandwidth from 2.9 nm to 9.3 nm, the scalar product ng×(Δλ)/λ from 0.1670 to 0.1926, and the ultralow-dispersion bandwidth from 1.6 nm to 3.5 nm by grading the eye-shaped scatterers along the transverse direction. It means that graded structures, especially the graded eye-shaped scatterers along the longitudinal direction, can achieve slow light effect well and may provide a new way to design and apply slow light..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1016003 (2013)
Optical Design and Fabrication
Influence of Distortion on TDI-CCD Space Camera and Its Suppression Method
Jin Guang, Ren Bingwen, and Zhong Xing
With the continuous development of the charge coupled device (CCD), the time delay integration charge coupled device (TDI-CCD) has become the first choice for high-resolution, large F number, compact space camera. However, due to the distortion of the optical system, in the process of TDI-CCD integral imaging, the imagWith the continuous development of the charge coupled device (CCD), the time delay integration charge coupled device (TDI-CCD) has become the first choice for high-resolution, large F number, compact space camera. However, due to the distortion of the optical system, in the process of TDI-CCD integral imaging, the image motion is inevitable, and eventually leads to the blurred image, and then image modulation transfer function (MTF) decreases. This paper analyzes the reason of the image motion caused by optical system distortion, and gives the expression of the MTF declined coefficient fMT,D by the distortion effects. From the point of view of optical system design, the method of restricting fMT,D is researched, and the results of the optical system design are given. Low distortion, wide field coaxial bias field fourth reflective optical system, with the focal length f′=9000 mm, F number of 13.33, and imaging spectral range of 400~700 nm, is designed. The design results demonstrate that the wavefront error is better than λ/21 and the fMT,D generated by the distortion is 0.969 in the using field angle 2ω=2°. It is proved that the system well suppresses the impact of distortion on integral imaging optical system. This study could provide the reference for high-resolution, wide field, large F number, and compact space camera design..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1022001 (2013)
Optical Design of Off-Axis Four-Mirror Optical System with Wide Field of View
Liu Jun, Liu Weiqi, Kang Yusi, Lü Bo, Feng Rui, Liu Hua, and Wei Zhonglun
Based on the third order aberration expression, basic design process of four-mirror optical system with aperture stop on secondary mirror are given through aberration analysis. Then a system with effective focal length of 1343 mm and field of view of 20°×0.6° is designed by making the field of y-directioBased on the third order aberration expression, basic design process of four-mirror optical system with aperture stop on secondary mirror are given through aberration analysis. Then a system with effective focal length of 1343 mm and field of view of 20°×0.6° is designed by making the field of y-direction off axis. The structure of this system is unobstructed and tight, with imaging qualities approaching diffraction limit. The designed system is suit for the field of space optical remote sensing..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1022002 (2013)
Optical Devices
Testing of a 9-Points Deformable Mirror and Its Application in Space Camera System
Chen Xindong
A 9-point active deformable mirror is designed according to the low order aberrations of space cameras, which can generate defocus, astigmatism and coma. The static and dynamic characters are tested. The testing results show that the static charater can reach 0.02λ(λ=632.8 nm) in several testing at 30 minutes time inteA 9-point active deformable mirror is designed according to the low order aberrations of space cameras, which can generate defocus, astigmatism and coma. The static and dynamic characters are tested. The testing results show that the static charater can reach 0.02λ(λ=632.8 nm) in several testing at 30 minutes time interval, and the repeatability accuracy is 0.01λ. The dynamic character is tested by the ‘Burst measure’ function of 4D interferometer. The response frequency is up to 28 Hz. The deformable mirror is applied to a space camera system as the fold mirror and the aberrations of the system are corrected. The testing results show that the root-mean-square (RMS) of wavefront is reduced from 0.122λ to 0.0896λ, and the modulation transfer function of system is improved from 0.364 to 0.428 at space frequency of 57.2 lp/mm. The test results verify the aberration correction ability of the deformable mirror..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1023001 (2013)
Photonic Crystal Transmission Spectrum with Parallel Alignment Nematic Liquid Crystal Defect
Wu Rina, Wu Jie, Li Yong, and Dai Qin
Transmission spectral properties of one-dimensional multilayer photonic crystal infiltrated with a parallel nematic liquid crystal are investigated. The range of photonic band gap is 518.5~582.0 nm when natural light is incident vertically to the glass substrate and paired transmission peaks are observed in photonic baTransmission spectral properties of one-dimensional multilayer photonic crystal infiltrated with a parallel nematic liquid crystal are investigated. The range of photonic band gap is 518.5~582.0 nm when natural light is incident vertically to the glass substrate and paired transmission peaks are observed in photonic band gap. One of the paired transmission peaks disappears in the case of adding a polarizer and making polarization direction parallel or perpendicular to rubbing direction with vertical incidence of polarized light. For an angle of 45° between polarization direction and rubbing direction, paired transmission still appears in photonic band gap. Optical wave has two eigenmodes (e- and o-mode) because of the anisotropy of liquid crystal layer. When the polarization direction of incident light is parallel to rubbing direction the optical wave is in e-mode, and when perpendicular to rubbing direction it is in o-mode. For the case of polarization direction and rubbing direction at an angle of 45°, two modes coexist..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1023002 (2013)
Dye-Sensitized Solar Cells Employing Graphene Nanosheets as Counter Electrode
Xu Shunjian, Luo Yufeng, Zhong Wei, Xiao Zonghu, and Luo Yongping
Ball-milled flake graphite is first employed as precursor to synthesize graphene nanosheets (GNs) by a technique of oxidation-reduction to study the change of crystal structure. The GNs are then used as catalytic materials for counter electrode in dye-sensitized solar cells (DSCs), and the influence of the succeeding hBall-milled flake graphite is first employed as precursor to synthesize graphene nanosheets (GNs) by a technique of oxidation-reduction to study the change of crystal structure. The GNs are then used as catalytic materials for counter electrode in dye-sensitized solar cells (DSCs), and the influence of the succeeding heat treatment of the GNs counter electrode on the photovoltaic properties of the device is finally investigated. Results show that the crystal structure of the GNs is improved by introducing the ball-milling of flake graphite, the thickness of the GNs is reduced and the distance d(002) of graphene layer is increased. Compared with the GNs prepared from natural flake graphite, the improved GNs as catalytic materials have higher catalytic activity and stronger capability of electrolyte diffusion, resulting in significant improvement in the efficiency of the DSCs. Through the heat treatment, the catalytic activity and the electrolyte diffusion capability of the GNs counter electrode are obviously strengthened, and the efficiency of the device is raised from 1.17% to 1.54% with an increment of 31.3%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1023003 (2013)
Remote Sensing and Sensors
Quantitative Analysis of the Measurement Precision of Phase Retrieval Wavefront Sensor
Ma Xinxue, Wang Jianli, Wang Bin, and Wang Zongyang
In order to validate the performance of phase retrieval wavefront sensor (PRWS), an experimental setup based on the PRWS method comparing with Zygo interferometer is built. The liquid crystal spatial light modulator (LC-SLM) is utilized to produce single aberration and random aberration, and the ability of PRWS measureIn order to validate the performance of phase retrieval wavefront sensor (PRWS), an experimental setup based on the PRWS method comparing with Zygo interferometer is built. The liquid crystal spatial light modulator (LC-SLM) is utilized to produce single aberration and random aberration, and the ability of PRWS measurement for any aberration is validated. The experimental results demonstrate that agreement is obtained among the errors distribution, peak valley (PV) value and root mean square (RMS) value of Zygo interferometer. The measurement precision of wavefront is 3λ/1000 (RMS). Therefore, the feasibility and accuracy of the proposed method can be confirmed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1028001 (2013)
Analysis and Simulation of Space-Time Speckle Effect Based on Synthetic Aperture Imaging Ladar
Xu Qian, Zhou Yu, Sun Jianfeng, Sun Zhiwei, Ma Xiaoping, Zhi Ya′nan, and Liu Liren
In synthetic aperture imaging ladar (SAIL), the image quality is seriously degraded by the laser speckle effect. Based on the SAIL system in far-field diffraction region, the physical models of laser speckle effect are established, and the expressions for the intensity of speckles are derived. The reasons of space-timeIn synthetic aperture imaging ladar (SAIL), the image quality is seriously degraded by the laser speckle effect. Based on the SAIL system in far-field diffraction region, the physical models of laser speckle effect are established, and the expressions for the intensity of speckles are derived. The reasons of space-time speckle effect are analyzed, and the specific speckle patterns are obtained. Research results indicate the statistical properties by simulating the phase and amplitude distribution of typical space-time speckle patterns. Simulation results show that the average width of speckle pattern equals the scale of footprint in SAIL system. The moving distance of speckle pattern along the range direction during a period of pulse time and the average speckle scale are roughly equivalent. Experiments are conducted on big aperture SAIL. Experimental results confirms the prediction. The vivid space-time speckle effect is firstly demonstrated. Simulation results provide a certain reference to the speckle reduction by using multi-channel transmitter/receiver..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1028002 (2013)
Scattering
Time Correlation Functions of Dynamic Speckle Produced by Rotating Cone Object
Yang Zhiqiang, Wu Zhensen, and Zhang Geng
Dynamic speckle is a speckle phenomenon that produced by moving diffuser with time. The space-time correlation functions of dynamic speckle and normalized time correlation functions are obtained under the situation that incident laser beam is perpendicular to cone rotation centerline. The space-time correlation functioDynamic speckle is a speckle phenomenon that produced by moving diffuser with time. The space-time correlation functions of dynamic speckle and normalized time correlation functions are obtained under the situation that incident laser beam is perpendicular to cone rotation centerline. The space-time correlation functions of dynamic speckle show that statistical properties of dynamic speckle are related to the rotation speed, radius of curvature, micro-structure and optical geometry structure. The dynamic speckle images produced by cone with different rotation speeds are measured. Normalized time correlation functions of polytetrafluoroethylene (PTFE) cone and duralumin cone with different rotation speeds are calculated, which shows that the normalized time correlation functions decrease sharply when the speed increases, and the normalized time correlation functions of duralumin fall faster than that of PTFE at the same rotation speed. The results of experiment are similar to that of formula derivation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1029001 (2013)
Spectroscopy
Efficient Algorithms for Echelle Spectrograph Design and Cross-Dispersed Spectra Analysis
Chen Shaojie, Bayanheshig, Pan Mingzhong, Zhu Jiwei, Song Ying, and Qi Xiangdong
Echelle spectrograph has two-dimension spectra on the image plane for its cross-dispersion structure, which makes it hard to design and analysis. In order to overcome these difficulties, an efficient algorithm based on the limits of boundary is described. The mathematic model is developed between the system requirementEchelle spectrograph has two-dimension spectra on the image plane for its cross-dispersion structure, which makes it hard to design and analysis. In order to overcome these difficulties, an efficient algorithm based on the limits of boundary is described. The mathematic model is developed between the system requirements, structure parameters and two-dimension echelle spectra. This algorithm can obtain the echelle spectrograph parameters quickly according to the system requirements, and establish the echelle spectra using these parameters, and then the parameters are modified according the results of echelle spectra, which provide a valuable method for designing echelle spectrograph and analysing spectra. Utilizing this model an echelle spectrograph is designed with the wavelength range of 200~900 nm and the spectral resolution of 25000 at 200 nm. After the measurement, this configuration can meet the needs of system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1030001 (2013)
Interaction of Eu Atom 6p1/2nl (l=0, 2) Autoionizing Rydberg States
Yang Jinhong, Wang Xi, Shen Li, and Dai Changjian
In order to systematically study autoionization spectra of the Eu atom and discuss their spectral characteristics, the three-step isolated core excitation (ICE) is used in the present experiment. The atom is excited from its ground state via the 4f76s6p6P5/2 or 4f76s6p8P5/2 intermediate state to the 4f76sns (n=7 or 8) In order to systematically study autoionization spectra of the Eu atom and discuss their spectral characteristics, the three-step isolated core excitation (ICE) is used in the present experiment. The atom is excited from its ground state via the 4f76s6p6P5/2 or 4f76s6p8P5/2 intermediate state to the 4f76sns (n=7 or 8) or 4f76s7d Rydberg state, from which it is further populated to the 4f76p1/2ns (n=7 or 8) or 4f76p1/27d autoionizing state. Not only the profound interaction between the 4f76p1/2ns (n=7 or 8) and 4f76p1/2nd autoionization Rydberg series revealed, but also the fingerprints of other series mixed in the 4f76p1/2ns (n=7 or 8) autoionization spectrum are identified. Moreover, the information of level energy, line width and line shape of these autoionizing states is reported, while the validity of ICE method is discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1030002 (2013)
Improvement of Signal-to-Noise Ratio of Electromagnetically-Induced Transparency Spectra in the Ladder-Type Cesium 6S1/2-6P1/2-8S1/2 Atomic System
Liu Huifeng, Wang Jie, Yang Baodong, Wen Xin, Jin Gang, He Jun, and Wang Junmin
In order to obtain electromagnetically-induced transparency (EIT) spectra with high signal-to-noise ratio (SNR), EIT has been investigated based on the cesium (Cs) 6S1/2-6P1/2-8S1/2 ladder-type atomic system. When the probe laser which couples the Cs 6S1/2-6P1/2 transition is frequency locked to hyperfine transition anIn order to obtain electromagnetically-induced transparency (EIT) spectra with high signal-to-noise ratio (SNR), EIT has been investigated based on the cesium (Cs) 6S1/2-6P1/2-8S1/2 ladder-type atomic system. When the probe laser which couples the Cs 6S1/2-6P1/2 transition is frequency locked to hyperfine transition and the controlling laser scans over the Cs 6P1/2-8S1/2 hyperfine transition, the narrow EIT spectra with a flat background is observed, and the spectral SNR is improved. The signal intensity of EIT hyperfine structures depends on not only the alignment of controlling and probe beam, but also the intensity of the controlling laser in ladder-type system. Finally, the EIT spectra with high SNR is obtained..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1030003 (2013)
Thin Films
Spectroscopic Ellipsometry Characterization of Hydrogenated Amorphous Silicon Thin Film
He Jian, Li Wei, Xu Rui, Guo Anran, Qi Kangcheng, and Jiang Yadong
Hydrogenated amorphous silicon (a-SiH) thin film is a technologically important material in microelectronic and optoelectronic industry, and ellipsometry is one of the important thin film characterization tools. The effects of different optical models including Tauc-Lorentz (TL) model and Forouhi-Bloomer (FB) model on Hydrogenated amorphous silicon (a-SiH) thin film is a technologically important material in microelectronic and optoelectronic industry, and ellipsometry is one of the important thin film characterization tools. The effects of different optical models including Tauc-Lorentz (TL) model and Forouhi-Bloomer (FB) model on the structural and optical results of a-SiH thin film in ellipsometry analysis are investigated. It is indicated that the measured thin film thickness, roughness and optical constants using different models are inconsistent. The thin film thickness from TL model is closer to the one from scanning electron microscopy (SEM) and the roughness is more comparable to the empirical value corresponding to atomic force microscopy (AFM) result. Combining the published references, it′s found that the varied thin film thickness and roughness are due to the different optical descriptions. Meanwhile, under the condition of different mathematical processing and assumption, the difference between optical constants from FB model and TL model appears..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1031001 (2013)
Dispersive Properties of Optical Constants of SiO2 Films in the Visible and Infrared Regions
Liu Huasong, Wang Lishuan, Jiang Chenghui, Liu Dandan, Jiang Yugang, Wu Bingjun, and Ji Yiqin
Ion beam sputtering (IBS) and electron beam evaporation (EBE) are the common methods for preparing SiO2 films. The dispersive properties of SiO2 films which are prepared by IBS and EBE methods are studied in the visible and infrared regions with the methods of ellipsometry and spectrum fitting. In the visible band, theIon beam sputtering (IBS) and electron beam evaporation (EBE) are the common methods for preparing SiO2 films. The dispersive properties of SiO2 films which are prepared by IBS and EBE methods are studied in the visible and infrared regions with the methods of ellipsometry and spectrum fitting. In the visible band, the refractive index of SiO2 films is higher than bulk materials; in the infrared band, chemical defects of the two kinds of films are determined by the position of absorption. The results show that chemical defects of IBS SiO2 film are less than EBE SiO2 films, and there is only a small amount of H2O molecules and Si-OH chemical bond in IBS SiO2 films. However, besides the two kinds of defects there are other large amounts of Si-H chemical bond defects in EBE SiO2 films. This implies that there are more defects resulting from water chemical reaction in EBE SiO2 films than that in IBS SiO2 films. Therefore, the chemical defects can be effectively controlled by IBS method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1031002 (2013)
Ultrafast Optics
Ultrafast Optical Physic Properties of CdSeS Quantum Dots
An Meiying, Zhang Zhengbing, Jin Zuanming, Lin Xian, and Ma Guohong
The transient carrier dynamics of CdSeS quantum dots is investigated by time-resolved femtosecond pump-probe transmission spectroscopy method at different photon energies and pump energy densities. The experimental results show that the relaxation of excited state of CdSeS quantum dots have three processes. The first oThe transient carrier dynamics of CdSeS quantum dots is investigated by time-resolved femtosecond pump-probe transmission spectroscopy method at different photon energies and pump energy densities. The experimental results show that the relaxation of excited state of CdSeS quantum dots have three processes. The first one is a rapid relaxation process whose time scale is about 10 ps. The rapid process time constant increases when the pump energy density increases and is independent of the photon energy. We hold the opinion that the rapid process is caused by the carrier and the optical phonon scattering. The second relaxation process whose time constant is about 100 ps. The carrier relaxation time is independent of the pump energy density and photon energy. The component is associated with recombination via trap states. Then a slow decay process due to single exciton relaxation with a lifetime as long as nanoseconds can be observed. This process is attributed to inter-band relaxation. The transmission change increases with the increase of pump energy density at zero delay time. When the pump energy density increases to a certain extent, the transmission change under the zero delay gradually tend to be saturated..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1032001 (2013)
X-Ray Optics
Multiple Contrast Micro-Computed Tomography System Based on X-Ray Grating Imaging
Qi Juncheng, Ren Yuqi, Du Guohao, Chen Rongchang, Wang Yudan, He You, and Xiao Tiqiao
The third synchrotron radiation facility provides a brilliant source for X-ray imaging taking the advantages of its monochromaticity and tunability. For low-Z materials, X-ray grating based on differential phase contrast imaging can provide higher sensitivity than conventional X-ray imaging. Combined with computed tomoThe third synchrotron radiation facility provides a brilliant source for X-ray imaging taking the advantages of its monochromaticity and tunability. For low-Z materials, X-ray grating based on differential phase contrast imaging can provide higher sensitivity than conventional X-ray imaging. Combined with computed tomography (CT), it also can realize three-dimension high resolution imaging and measurement of refractive index. A set of X-ray grating based on imaging system is installed at the X-ray imaging and biomedical application beamline at Shanghai Synchrotron Radiation Faclity. Based on this system, three kinds of contrast including absorption, phase and scattering can be retrieved separately based on a single set of projections. According to test results for the standard sample of three different kinds of polymer, the refractive index decrement can be achieved. All these results demonstrate that the established X-ray grating imaging system can provide multiple contrast imaging and may play an important role in the nondestructive and quantitative imaging to biomedical and material samples..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1034001 (2013)
Integrated Development of Extreme Ultraviolet Lithography Mask at 32 nm Node
Du Yuchan, Li Hailiang, Shi Lina, Li Chun, and Xie Changqing
The first domestic 6 inch (1 inch=2.54 cm) extreme ultraviolet lithography (EUVL) mask for EUVL system is reported. The design of the 6 inch EUVL mask at 32 nm node is described, process characteristics of substrate materials, buffer and absorber layers are investigated in detail, and mask with low defective rate and hThe first domestic 6 inch (1 inch=2.54 cm) extreme ultraviolet lithography (EUVL) mask for EUVL system is reported. The design of the 6 inch EUVL mask at 32 nm node is described, process characteristics of substrate materials, buffer and absorber layers are investigated in detail, and mask with low defective rate and high efficiency is designed. Suitable Cr absorber layer thickness is decided according to the optical property simulation by finite-difference time-domain (FDTD) method. Electron beam proximity effect is analyzed by using Monte Carlo simulation method. Electron beam lithography is used to generate patterns, and high density plasma etching is used to translate patterns to the Cr absorber layer and SiO2 buffer layer. EUVL mask with critical dimension below 100 nm and critical dimension accuracy less than 20 nm is obtained, which meets the requirements of technical design specifications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 33, Issue 10, 1034002 (2013)
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