Contents
2012
Volume: 32 Issue 3
49 Article(s)
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Diffraction and Gratings
Profile Evolution of Grating Masks According to Exposure Dose and Interference Fringe Contrast in the Fabrication of Holographic Grating
Han Jian, Bayanheshig, Li Wenhao, and Kong Peng
In order to improve the precision control of the duty cycle and the groove depth of a recorded profile in the photoresist, based on the nonlinearity of the photoresist in development processing, a binary resist mathematical model for simulating the profile evolution of the photoresist grating is presented, according toIn order to improve the precision control of the duty cycle and the groove depth of a recorded profile in the photoresist, based on the nonlinearity of the photoresist in development processing, a binary resist mathematical model for simulating the profile evolution of the photoresist grating is presented, according to this model, the changing of the profile characteristics such as duty cycle and the groove depth which depend on the contrast and exposure dose can easily be understanded. It turns out that: under specific development condition and the exposure upper limit Ec recognized by calculating and experiment, the duty cycle of the grating masks decreases as the exposure dose increases, the decrease of fringe contrast not only results in the decrease of the duty cycle, but also results in the decrease of the groove depth. The model can show the profile evolution trend exactly, it provides a right analysis tool for forecasting and controlling the groove shape in the fabrication of the grating masks..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 305001 (2012)
Study of the Effect of Aperture Transmittance Modulation on Heterodyne Detection
Dong Hongzhou, Wu Jian, and Guo Zhenzhen
The angel between signal light and local light is an important factor to the heterodyne detection. When the angle is too large, one even cannot detect the heterodyne signal. It is proposed that the amplitude of heterodyne signal output by detection is just the Fourier transform of aperture transmittance function. BasedThe angel between signal light and local light is an important factor to the heterodyne detection. When the angle is too large, one even cannot detect the heterodyne signal. It is proposed that the amplitude of heterodyne signal output by detection is just the Fourier transform of aperture transmittance function. Based on the theory, a method that can reduce the influence of spatial mismatch angle on heterodyne detection is proposed. Namely, if a component whose transmittance is a certain function is placed on the aperture surface and the Fourier transform of the function meets certain requirement, one can find that the amplitude of heterodyne signal may be enhanced when the angle between the two beams becomes large, which can reduce the requirement for pointing accuracy of detection system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 305002 (2012)
Fiber Optics and Optical Communications
Research on Multi-Channel Access Technology in Wireless UV Scattering Communication
Zhao Taifei, Wang Xiaorui, and Ke Xizheng
The multi-channel access technology of MAC (Media Access control) is studied for wireless UV light scattering communication. The three modes of UV (ultraviolet light) NLOS (no-line-of-sight) communication are analyzed. Multi-interface and multi-channel sets of UV transceiver are deployed in each node. Both the communicThe multi-channel access technology of MAC (Media Access control) is studied for wireless UV light scattering communication. The three modes of UV (ultraviolet light) NLOS (no-line-of-sight) communication are analyzed. Multi-interface and multi-channel sets of UV transceiver are deployed in each node. Both the communication node model and the UV channel model are established, and the access technology of multi-channel is studied. Three modes of UV NLOS multi-channel communication are stimulated in different topologies with NS2. The results show that the UV multi-channel access technology can increase the effective network throughput with using multiple channels..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306001 (2012)
Experimental Investigation for 60 GHz Radio-Over-Fiber System Employing Orthogonal Frequency-Dioision Multiplexing Format Based on Companding Transform
Chen Hongxian, Chen Lin, Yu Jianjun, Xiao Jiangnan, Cao Zizheng, and Li Fan
A 60 GHz orthogonal frequency-division multiplexing (OFDM) radio-over-fiber (ROF) system based on companding transform technique is proposed and experimently demonstrated to reduce the peak-to-average power ratio (PAPR) of OFDM signals and improve the sensitivity of the receiver. The 2.5 Gb/s 60 GHz OFDM-ROF signals baA 60 GHz orthogonal frequency-division multiplexing (OFDM) radio-over-fiber (ROF) system based on companding transform technique is proposed and experimently demonstrated to reduce the peak-to-average power ratio (PAPR) of OFDM signals and improve the sensitivity of the receiver. The 2.5 Gb/s 60 GHz OFDM-ROF signals based on companding transform is transmitted over 50-km standard single-mode fiber in the system. The experimental results show that the PAPR of the OFDM signal is decreased by 3 dB at complementary cumulative distribution function (CCDF) level of 10-4, and the receiver sensitivity is improved by 2.3 dB for launch power of 12 dBm at the BER of 10-3 and without dispersion compensation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306002 (2012)
Channel Capacity of Optical Multiple Input Multiple Output System without Background Noise
Wang Huiqin, Cao Minghua, Chen Haiyan, Hu Jiaqi, and Ke Xizheng
Channel capacity is the maximal transmission ratio of the communication system. It is one of the important indexes to measuring system communication ability. The channel model of the optical multi-in and multi-out (MIMO) system is established, then the ergodic channel capacity and outage capacity of optical MIMO systemChannel capacity is the maximal transmission ratio of the communication system. It is one of the important indexes to measuring system communication ability. The channel model of the optical multi-in and multi-out (MIMO) system is established, then the ergodic channel capacity and outage capacity of optical MIMO system are analyzed by combining pulse position modulation (PPM). And then, the in-closed approximate expressions of ergodic channel capacity are deduced with and without fading in the case of no background radiation, respectively. It shows that the channel capacity of optical MIMO system can be doubly raised under the condition of same sending power and bandwidth. Its feasibility is confirmed using Monte Carlo simulation experiment..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306003 (2012)
Research on the Refractive-Index Gradient Sensor Based on the Structured Fiber Bragg Grating
Luo Binbin, Zhao Mingfu, Zhou Xiaojun, Shi Shenghui, Cao Yang, Han Xi, and Cao Xuemei
The responsive characteristics of the structured fiber Bragg grating (FBG) under liquid medium with the refractive-index (RI) linear distribution are analyzed. The simulated results show that the reflection spectrum of the structured FBG are closely related to the properties of the RI distribution function of the liquiThe responsive characteristics of the structured fiber Bragg grating (FBG) under liquid medium with the refractive-index (RI) linear distribution are analyzed. The simulated results show that the reflection spectrum of the structured FBG are closely related to the properties of the RI distribution function of the liquid medium, such as the RI gradient along its axis and the value of the RI at both of its ends. Based on the numerical results, the theoretical model for the linear-approximation measurement of the RI gradient of the liquid medium by the structured FBG at the low RI area (1.330~1.360) is established. Through the experiments, the feasibility of the theoretical simulations and analyses and the practical applications of the RI gradient sensor based on the structured FBG are verified..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306004 (2012)
Experimental Investigation on Superfluorescent Sources Based on Erbium-Doped Photonic Crystal Fiber
Wu Xu, Ruan Shuangchen, Liu Chengxiang, and Zhang Li
In order to improve the stability of conventional erbium-doped superfluorescent fiber source, a superfluorescent fiber source based on erbium-doped photonic crystal fiber was proposed. A superfluorescent fiber source with a single-pass backward configuration was constructed and the output properties of the new fiber soIn order to improve the stability of conventional erbium-doped superfluorescent fiber source, a superfluorescent fiber source based on erbium-doped photonic crystal fiber was proposed. A superfluorescent fiber source with a single-pass backward configuration was constructed and the output properties of the new fiber source were researched. The influences of fiber length and pump power on output power, spectral width and mean wavelength of fiber source were analyzed. By choosing the optimized fiber length of 28 m and pump power of 220 mW, the superfluorescent fiber source had an output power of 45.74 mW, an optical-to-optical conversion efficiency of 20.79 %, a spectral width of 31.5 nm and a mean wavelength of 1548.003 nm. This result would set the foundation to further investigate the stability of erbium-doped photonic crystal fiber superfluorescent source in the different environment..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306005 (2012)
Influence of Nonlinear Effects in 112 Gbit/s Transmission Co-Propagating Multi-Rate Neighbors
Lin Mi, Zhang Yang′an, Zhang Jinnan, Zhang Minglun, and Huang Yongqing
Nonlinear tolerance of 112 Gbit/s polarization-multiplexed differential quadrature phase-shift keying signal over long-haul transmission with different types of neighboring channels, and with a cascade of 50-GHz grid is increased. The result indicates considerable tolerance to nonlinear effects is observed and proves tNonlinear tolerance of 112 Gbit/s polarization-multiplexed differential quadrature phase-shift keying signal over long-haul transmission with different types of neighboring channels, and with a cascade of 50-GHz grid is increased. The result indicates considerable tolerance to nonlinear effects is observed and proves the feasibility of 112 Gbit/s overlaying existing 10 Gbit/s or 43 Gbit/s commercial systems despite the presence of strong cross-phase modulation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306006 (2012)
Research of High-Speed Large-Capacity Fiber Bragg Grating Demodulator
Li Zhengying, Zhou Zude, Tong Xinglin, Xiong Tao, Tang Zhihao, Cai Linjun, and Zhao Meng
A four-channel large-capacity, high-speed fiber Bragg grating demodulator is proposed. It constitutes of semiconductor optical amplifier and tunable Fabry-Pérot filter which is composed a high-speed scan laser in a loop structure, combining the optical coupler, optical loop circuit and photodiode. A 2 kHz triangulA four-channel large-capacity, high-speed fiber Bragg grating demodulator is proposed. It constitutes of semiconductor optical amplifier and tunable Fabry-Pérot filter which is composed a high-speed scan laser in a loop structure, combining the optical coupler, optical loop circuit and photodiode. A 2 kHz triangular-like modulation signal is used in this system to drive the Fabry-Pérot filter to make fast scan in the range of 50 nm. The nonlinear effect and scan wavelength shift can be eliminated in Fabry-Pérot filter by introducing the reference channel composed by optical fiber comb filter and single-peak filter, leading to the excellent stability and linearity of demodulator. The stability of high-speed fiber Bragg grating demodulator is 2 pm; the resolution is 1 pm; the linearity is 0.99957; the measuring accuracy is 5 pm, the demodulation frequency is 2 kHz..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 306007 (2012)
Holography
Research on Issues about Reconstructed Holographic Image Based on a Pixelated Spatial Light Modulator
Shen Chuan, Zhang Cheng, Liu Kaifeng, Wei Sui, Cheng Hong, and Zhang Qing
When utilizing the phase-only spatial light modulator (SLM) for holographic display, the visual impression of reconstructed image is disturbed by multi-order diffraction beams and multi-order reconstructed images because of the pixelated structure of the SLM. After the effects of a pixelated SLM with a limited fill facWhen utilizing the phase-only spatial light modulator (SLM) for holographic display, the visual impression of reconstructed image is disturbed by multi-order diffraction beams and multi-order reconstructed images because of the pixelated structure of the SLM. After the effects of a pixelated SLM with a limited fill factor on the reconstructed image are analyzed, the method that improves the visual impression of reconstructed image and adjusts the position and size of the image is investigated. Firstly, synthesizing phase-only hologram and digital blazed grating, subsequently adding the phase of the convergent spherical wave, the two focus planes of reconstructed image and the multi-order beams caused by the pixelated structure of the SLM can be separated. Then both the aperture and the high pass filter are used to eliminate the influences of higher diffraction orders, multi-order images and zero order light on the visual impression of reconstructed image simultaneously. Eventually an imaging lens is used to adjust position and size of the reconstructed image. A holographic display system based on liquid crystal on silicon (LCOS) is set up to demonstrate this method. The experimental results show that the final reconstructed image not only has good quality but also has the conveniently adjustable position and size. This method can also be applied to various optical systems based on pixelated SLMs..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 309001 (2012)
Imaging Systems
Denoising of Eelectronic Speckle Interferogram Based on Improved Spin Filtering
Jia Dagong, Ma Caibin, Wu Liqiang, Zhang Hongxia, and Zhang Yimo
Speckle noise is inevitably involved in fringe pattern in electronic speckle pattern interferometry (ESPI), removing the noise is an important issue in ESPI. By exploiting the directionality of speckle pattern, an improved spin filtering is presented: four fuzzy directional windows in the field of current point are defSpeckle noise is inevitably involved in fringe pattern in electronic speckle pattern interferometry (ESPI), removing the noise is an important issue in ESPI. By exploiting the directionality of speckle pattern, an improved spin filtering is presented: four fuzzy directional windows in the field of current point are defined, so as to turn the determination of accurate one-dimensional directional window is turned into the determination of fuzzy directional window, and then the adaptive weighted mean filtering is applied instead of traditional median filtering is applied as denoising in the determined direction. The performance of the improved spin filtering is analyzed by using both computer-simulated fringes and experimental fringe. Bilateral filtering, wavelet subband removal method are introduced for making a comparison and validation in the image processing effect. The experimental results show that the proposed method is effective in noise removal and edge preservation for ESPI images..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 311001 (2012)
L1-Norm-Based Differential Phase-Contrast Computerized Tomography Reconstruction Algorithm with Sparse Angular Resolution
Li Jing, and Sun Yi
Differential phase contrast computerized tomography (DPC-CT) is a novel X-ray inspection method. However, DPC-CT usually requires several sampling attempts, which will inevitablly introduce unacceptabe long exposure time and huge X-ray doses. Sparse angular algorithms show significant advantage in reducing the exposureDifferential phase contrast computerized tomography (DPC-CT) is a novel X-ray inspection method. However, DPC-CT usually requires several sampling attempts, which will inevitablly introduce unacceptabe long exposure time and huge X-ray doses. Sparse angular algorithms show significant advantage in reducing the exposure time and X-ray doses. Thus, the study of sparse angular DPC-CT is particularly important. After analyzing the characteristics of the DPC-CT, we introduce the compressive sensing theory into the DPC-CT reconstruction and propose a reconstruction algorithm for DPC-CT named as ART-L1 algorithm which fuse the L1 constraint into the ART algorithm. The numerical simulation and experimental results show that the ART-L1 algorithm can significantly improve the image quality of the sparse angular DPC-CT reconstructions..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 311002 (2012)
Instrumentation, Measurement and Metrology
Study on Calibration Environment of Spectral Responsivity for Space Ultraviolet Remote Sensing Instrument
Zhang Zhenduo, Wang Shurong, Li Hongzhuang, Wei Peifeng, and Wang Liang
Reducing the radiometric calibration uncertainty of the space ultraviolet remote sensing instrument (SURSI) in laboratory is very important to improve the instrument′s detection accuracy in orbit. A deep study on the calibration environment of SURSI is made. The Al+MgF2 film reflectivity of 250~400 nm in vacuum/air envReducing the radiometric calibration uncertainty of the space ultraviolet remote sensing instrument (SURSI) in laboratory is very important to improve the instrument′s detection accuracy in orbit. A deep study on the calibration environment of SURSI is made. The Al+MgF2 film reflectivity of 250~400 nm in vacuum/air environment are calculated by the film electromagnetic theory and two results are compared. The experiment is completed, which is study on the discrepancy in the SURSI spectral responsivity when it is at different environments by establishing SURSI responsivity vacuum/air comparison system. The average deviation is about 3.8% from 250 to 400 nm. Theoretical analysis and measurement result show that because they are affected by the optical properties of Al+MgF2 film which are decided by optical components inside the SURSI, the spectral responsivities of SURSI have distinct difference in vacuum/air environment and the deviation depends on wavelength. It is necessary to make the radiation calibration of SURSI in vacuum environment..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 312001 (2012)
Research of Acousto-Optical Gyroscope Based on Polarization-Mode Conversion
Lu Shuxiang, Chen Shufen, Fu Lei, Zou Zhengfeng, and Meng Yanbin
A type of acousto-optic gyroscope based on polarization-mode conversion is presented, the principle and structure is analyzed and some tests of the gyroscope are carried out. The sensitivity of sensor is also given. The statical result shows that the coupling efficient is 80.02% when the length of acousto-optic interacA type of acousto-optic gyroscope based on polarization-mode conversion is presented, the principle and structure is analyzed and some tests of the gyroscope are carried out. The sensitivity of sensor is also given. The statical result shows that the coupling efficient is 80.02% when the length of acousto-optic interaction is 15 mm, the input electrical power of surface acoustic wave (SAW) is 100 mW and the frequency of SAW is 168.201 MHz. A linear voltage-rotation response curve of the gyroscope is obtained when rotating, and the sensitivity is 1 mV/[(°)/s]. Acousto-optic gyroscope based on polarization-mode conversion keeps the advantage of SAW gyroscope, and the sensitivity is enhanced greatly..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 312002 (2012)
Vibration Measurement System Based on the Crystal BSO
Zhang Bin, Feng Qibo, You Fengling, and Gao Xiaojing
A high-frequency mirco-vibration measurement system based on the photorefractive crystal is presented. The homodyne interferometer configuration is adopted and the crystal Bi12SiO20 (BSO) is used to record the dynamic holographic signal formed by the interference of the signal beam and the reference beam. SimultaneouslA high-frequency mirco-vibration measurement system based on the photorefractive crystal is presented. The homodyne interferometer configuration is adopted and the crystal Bi12SiO20 (BSO) is used to record the dynamic holographic signal formed by the interference of the signal beam and the reference beam. Simultaneously, the diffracted reference beam is generated and interferes on the photodetector with the partial signal beam transmitted directly through the crystal. Time-based signals of photocurrent which is proportional to the vibration displacement are obtained. The factors that affect diffraction efficiency have been investigated such as intensity ratio of the reference beam and the signal beam, the angle between the above two beams. Another quarter-wave plate is used in the reference beam path to improve the measuring sensitivity without electric field on the crystal. A piezoelectric ceramic is used as the target and the detected frequency by this system exactly corresponds to the predetermined frequency from 0.5 kHz to 90 kHz..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 312003 (2012)
Beam Scanning and Wind Inversion Technique of a Mobile Doppler Lidar
Shen Fahua, Sun Dongsong, Wang Zhongchun, Xue Xianghui, Chen Tingdi, and Dou Xiankang
During the field campaign, after taking into account the randomness of the working platform, the measuring coordinate system of the mobile Doppler lidar may no longer be the ground reference frame, which will lead to difficulty for the three-dimensional vector wind field inversion. Three-dimensional space coordinate roDuring the field campaign, after taking into account the randomness of the working platform, the measuring coordinate system of the mobile Doppler lidar may no longer be the ground reference frame, which will lead to difficulty for the three-dimensional vector wind field inversion. Three-dimensional space coordinate rotation transformation method is proposed to establish the general relation between the measurement coordinate system and the ground reference frame, and then a general formula for three-dimensional wind field inversion is derived. In addition, in the process of beam scanning, due to the restriction of two-dimensional scanner machining precision and other limitations, there is a certain orientation error of the laser beam. The wind field measurement errors caused by beam pointing deviation are studied quantitatively by using Monte-Carlo simulation method. The results show that when the horizontal wind speed is 100 m/s, the horizontal wind speed error is 0.712 m/s and wind direction error is 0.704° for 1° beam orientation error, which is consistent with the theoretical results. The results of theoretical analysis also show that when the horizontal wind speed is 100 m/s, the maximum deviations of horizontal wind speed and direction would be 1.16 m/s and 1° respectively for 1° maximum deviation of beam direction..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 312004 (2012)
Camera Calibration and Attitude Measurement Technology Based on Astronomical Observation
Dai Dongkai, Wang Xingshu, Hu Chunsheng, and Jiao Hongwei
To realize high precision attitude measurement by means of astronomical observation with a camera, it is quite necessary to calibrate the parameters of the camera accurately. A camera calibration method is presented based on astronomical observation to solve the problem that the traditional calibration methods can onlyTo realize high precision attitude measurement by means of astronomical observation with a camera, it is quite necessary to calibrate the parameters of the camera accurately. A camera calibration method is presented based on astronomical observation to solve the problem that the traditional calibration methods can only work effectively in a limited distance. The world coordinates of control points at the measuring time are calculated by using the spherical astronomy method. A star observation model is established according to the photogrammetric principle, both the external and intrinsic parameters of the camera are obtained, and the calibration precision is also analyzed. The experimental results indicate that the calibration method can achieve a good precision without the aid of precise and complex equipment, and the method performs also well when noise exists. Finally, the calibration result is adopted to work out the attitude of the camera, and the obtained repeatability accuracy of yaw and pitch angle is better than 10″. This method can be applied to the calibration of star sensor..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 312005 (2012)
Dichromatic Interferogram of Lubricant Film Measurement
Zhou Guangmei, Guo Feng, and Li Hongsheng
The multi-beam interference and the CCD camera spectral response, a colorimetric model is established for the interference measurement of lubricating-film thickness. A computation program is built for rendering the interferograms generated by a dichromatic light source in the lubricating-film measurement. For a static The multi-beam interference and the CCD camera spectral response, a colorimetric model is established for the interference measurement of lubricating-film thickness. A computation program is built for rendering the interferograms generated by a dichromatic light source in the lubricating-film measurement. For a static ball-glass disc contact, the results of theoretical simulation and experiment of the red-green dichromatic interferograms are agreed. Analyses show that the dichromatic interferogram is mainly influenced by the full width of half maximum (FWHM) of the green-red filter, the thickness of the beam splitter, the spacer thickness and the lubricants. A small FWHM, 4~10 nm of the beam splitter thickness and low spacer thuickness can lead to high contrast of interference fringes..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 312006 (2012)
Integrated Optics
Opto-Fluidic Tactile Sensor Array by Laser Direct Writing
Li Xian, Yuan Yufeng, Li Shu, Lin Qiao, Fan Yuqiang, and Wu Xingkun
A tactile sensor element is designed and fabricated based on laser direct writing technology. A continuous measurement of external tactile pressure is achieved by using an optical microfluidic structure. The tactile sensing element is fabricated using ultraviolet laser direct writing technology combining with a high-prA tactile sensor element is designed and fabricated based on laser direct writing technology. A continuous measurement of external tactile pressure is achieved by using an optical microfluidic structure. The tactile sensing element is fabricated using ultraviolet laser direct writing technology combining with a high-precision translation stage, and the overall process time is within 3 min. Experimental results show that the relation between external pressure and change in light intensity exhibits a smooth curve with a sensitivity of 0.995 mV/kPa. The array structure is designed and fabricated based on this sensing element, and it is capable of not only eliminating optical accumulated error, but also enhancing integration of optical tactile sensing into various applications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 313001 (2012)
Lasers and Laser Optics
Experimental Investigation on 1018 nm Fiber Laser and Tandem Pumping
Xiao Hu, Dong Xiaolin, Zhou Pu, Xu Xiaojun, and Zhao Guomin
Cascaded all-fiber 1018 nm laser source is designed and demonstrated, which can boost the low input 1018 nm signal to 4.2 W. The main factors that have impact on the power conversion efficiency are analyzed. Then the tandem-pumped fiber amplifier is experimentally investigated in which the 1018 nm fiber laser is used aCascaded all-fiber 1018 nm laser source is designed and demonstrated, which can boost the low input 1018 nm signal to 4.2 W. The main factors that have impact on the power conversion efficiency are analyzed. Then the tandem-pumped fiber amplifier is experimentally investigated in which the 1018 nm fiber laser is used as pump source to amplify the 1070 nm signal laser. In the core-pumping experiment, the signal laser is efficiently amplified with a high power conversion efficiency. The reason leading to low power conversion efficiency in cladding-pumped experiment is analyzed and some solutions are proposed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 314001 (2012)
Investigation on Characteristics of Mode Hopping in Ultra-Narrow Linewidth Erbium-Doped Fiber Ring Laser under Pump Modulation
Ma Mingxiang, Yang Huayong, Xu Pan, Hu Zhengliang, and Hu Yongming
One type of mode-hopping detection system based on fiber Michelson interferometer is set up. The influence of pump modulation on the mode-hopping characteristics of ultra-narrow linewidth erbium-doped fiber ring laser is investigated experimentally through the system. The mode-hopping map of laser labeled by pump curreOne type of mode-hopping detection system based on fiber Michelson interferometer is set up. The influence of pump modulation on the mode-hopping characteristics of ultra-narrow linewidth erbium-doped fiber ring laser is investigated experimentally through the system. The mode-hopping map of laser labeled by pump current is measured to reveal the mode-hopping characteristics. Numerical results show that the laser will orderly experience steady single-mode area, unsteady single-mode area and multimode area with the pump current increasing, and there exists a second threshold over which the laser will hop from single-mode into drastic multimode. Besides, frequency drift going with serial mode hops can be excited by pump-induced thermal effect or hostile disturbances applied on the laser cavity..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 314002 (2012)
Tunable Two-Frequency Solid-State Laser with Coupled-Cavity Configuration
Wu Xia, Yang Suhui, Chen Ying, Zhao Changming, and Liu Zhijie
A laser-diode-pumped two-frequency solid-state laser with tunable frequency difference is investigated, the principle of coupled-cavity is presented. Single-longitudinal mode oscillation is obtained from a coupled-cavity setup. Two quarter-wave plates are inserted to lift the degeneration of frequencies in orthogonal pA laser-diode-pumped two-frequency solid-state laser with tunable frequency difference is investigated, the principle of coupled-cavity is presented. Single-longitudinal mode oscillation is obtained from a coupled-cavity setup. Two quarter-wave plates are inserted to lift the degeneration of frequencies in orthogonal polarizations. 34 mW output power of two-frequency laser with tunable frequency difference is achieved. The beat note frequency can be continuously tuned from 0 to 1.1 GHz..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 314003 (2012)
Machine Vision
Parallel Edges Detection from Remote Sensing Image Using Local Orientation Coding
Wang Wenfeng, Zhu Shuhua, Feng Yihao, and Ding Weili
In order to solve the difficulty for extraction of roads, buildings and rivers from high-resolution remote sensing images, a new parallel feature detection algorithm based on edge directional information is proposed in this paper. Firstly, parallel edges model is defined as boundaries made up of parallel short lines. TIn order to solve the difficulty for extraction of roads, buildings and rivers from high-resolution remote sensing images, a new parallel feature detection algorithm based on edge directional information is proposed in this paper. Firstly, parallel edges model is defined as boundaries made up of parallel short lines. Then, the methods of 8-neighborhood boundary-tracking based on collinear restriction in junction points and line detection algorithm in 9-pixels sliding window are proposed to obtain the local directional codes of edge chains. Finally, two efficient criterions are presented to extract the parallel features based on the principal component analysis and the consistency of edge coding. Experimental results show that the proposed algorithm is effective for extracting the nearest parallel lines and curves from high-resolution remote sensing images, and the average accuraty is more than 95%, but the running speed needs further improvement..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 315001 (2012)
Large-Scale Three-Dimensional Stereo Vision Geometric Measurement System
Zhang Xuping, Wang Jiaqi, Zhang Yixin, Wang Shun, and Xie Fei
Large-scale three-dimensional vision measurement based on stereo vision is an effective and flexible method for precise space coordinates measurement when the object′s shape is irregular and the size is relatively large. Different from traditional methods, the accuracy of large-scale vision measurement degrades with diLarge-scale three-dimensional vision measurement based on stereo vision is an effective and flexible method for precise space coordinates measurement when the object′s shape is irregular and the size is relatively large. Different from traditional methods, the accuracy of large-scale vision measurement degrades with distance rapidly. Meanwhile, it is hard to control the illumination under large-scale condition, which also makes the measurement quite unsteadily. Thus how to maintain the accuracy under large-scale situation becomes the key technique problem to be solved. The principle of the vision measurement system is introduced. The factors which affect the measuring accuracy are analyzed. Structured light extraction method with phase congruency and epipolar constraint is proposed which can increase the image analysis accuracy obviously. A prototype is developed and the experimental results show that the proposed method is of high accuracy and large measuring range..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 315002 (2012)
Calibration Method for Binocular Vision Based on Matching Synthetic Images of Concentric Circles
Hou Junjie, Wei Xinguo, and Sun Junhua
The mathematical model of a binocular vision sensor is analyzed. A novel calibration method for binocular vision sensor based on matching the synthetic images of concentric circles is proposed. The target of concentric circles is randomly placed in the field of vision sensor for several times and the images of target aThe mathematical model of a binocular vision sensor is analyzed. A novel calibration method for binocular vision sensor based on matching the synthetic images of concentric circles is proposed. The target of concentric circles is randomly placed in the field of vision sensor for several times and the images of target are acquired by two cameras. The synthetic images are calculated through the model of camera and the known position of concentric circles in the target plane. By matching the synthetic images and observed images, the coordinate of the centre circles in image plane is located with optimization. Then, based on the image coordinate of the concentric circles in two cameras and the constraint of binocular vision, the parameters of binocular vision sensor are optimized by Levenberg-Marquart method. Based on the calibration proposed by Z.Y.Zhang, the whole information of the images is optimized. The experiment shows that the accuracy of calibration is improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 315003 (2012)
Materials
Two-Dimensional Left-Handed Material Based on Parallel Metallic Double Rods in Terahertz Wave
Liang Lanju, Yan Xin, Yao Jianquan, Tian Guicai, and Xue Dong
Negative permittivity can be realized from the periodic unit cells of the metallic bar structure. Two-dimensional left-handed material based on metal-rod pair structure is proposed. Propagation characteristics of two-dimensional left-handed material are studied by the time-domain finite integration method. Simulation sNegative permittivity can be realized from the periodic unit cells of the metallic bar structure. Two-dimensional left-handed material based on metal-rod pair structure is proposed. Propagation characteristics of two-dimensional left-handed material are studied by the time-domain finite integration method. Simulation shows that the structure has good left-handed property at the frequency of about 0.76 THz. Results indicate that this construction exhibits negative equivalent permittivity and permeability simultaneously in 0.75~0.78 THz, and the double negative pass band is 0.03 THz. Double negative pass band changing with structural parameter of metallic rod pairs is studied, indicating that it is related with the space between metallic rod pair, length and substrate thickness. The results provide a certain reference to design and study of left-handed material in terahertz range..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 316001 (2012)
Medical Optics and Biotechnology
Raman Spectroscopic Profile of Ethanol Fermentation in High Gravity Cassava Starch Brewing
Li Zida, Lai Junzhuo, Liao Wei, Liu Junxian, and Wang Guiwen
Raman spectroscopy is used to characterize the process of ethanol fermentation and look into the Saccharomyces cerevisiae cells at single-cell level. The ethanol fermentation using high-concentration cassava starch as feedstock is processed in a 500 L fermentor and the Raman spectra of substrate, product and individualRaman spectroscopy is used to characterize the process of ethanol fermentation and look into the Saccharomyces cerevisiae cells at single-cell level. The ethanol fermentation using high-concentration cassava starch as feedstock is processed in a 500 L fermentor and the Raman spectra of substrate, product and individual yeast cell are acquired by using laser tweezers Raman spectroscopy (LTRS). Major results are as follows: 1) Raman spectroscopy can monitor the dynamic changes of substrate and product during the ethanol fermentation; 2) the changes of intracellular components of yeast cells exhibit three stages, i.e., primary fermentation, main fermentation and later fermentation, which are similar to those of products, but there is a delay of about 4 h; 3) yeast cells amend its physiological state and intracellular compounds to adapt to the high osmotic stress at the initial stage and the high ethanol concentration at the later stage of fermentation. Random coiling dominates the secondary structure of yeast protein as the ethanol concentration increases; 4) purine is synthesized and accumulated in yeast cells at the later stage, but the amounts of individual cells are greatly heterogeneous. This work provides beneficial reference on the ethanol fermentation from a new perspective. LTRS shows the potential to open a new frontier of microbial fermentation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 317001 (2012)
Visual Cell Concentration Effect on the Polarization of Scattered Light
Ye Haishui, Gao Zhishan, He Jun, Li Yang, and Qin Zhenyu
Human′s eye is a biological tissue with high scattering. Analysis on light propagation in human′s eye based on Mie theory has great significance on the research of multi-scattering imaging in biological tissue. According to the anatomical retinal structure and cellular distribution, a static structure factor from molecHuman′s eye is a biological tissue with high scattering. Analysis on light propagation in human′s eye based on Mie theory has great significance on the research of multi-scattering imaging in biological tissue. According to the anatomical retinal structure and cellular distribution, a static structure factor from molecular dynamics is introduced to revise the radiative transfer theory, and the polarization of scattered light is numerically solved by the discrete ordinate method (DOM). The numerical results show that the polarization of scattered light depends on the cellular size and concentration distribution etc. Light polarization fluctuates for different polar angles and optical paths, and cone nucleus has more intrinsic polarization than rod nucleus. The variance of scattered light polarization increases as the scattering angle increases..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 317002 (2012)
Microscopy
New Method of Spatial Differential Imaging with Confocal Microscope
Zhang Man, Tang Zhilie, Tan Zhiliang, Wu Yongbo, Liao Yanfei, and Guo Lina
A new method for obtaining the spatial differential confocal microscopic image is presented. In order to realize spatial differential confocal microscopy, an optical complementary chopper is designed based on time-resolved technology to achieve the differential of signals. Combining with confocal scanning technology, uA new method for obtaining the spatial differential confocal microscopic image is presented. In order to realize spatial differential confocal microscopy, an optical complementary chopper is designed based on time-resolved technology to achieve the differential of signals. Combining with confocal scanning technology, using the different signals of confocal microscope the spatial differential confocal microscopic image is obtained. Through experiments, the rationality of the system is approved. The spatial differential confocal microscopic images of integrated circuit maskplate are measured on this system. The results show that the spatial differential confocal microscopy can gain edge profile of imaging objects and enhance image edge compared to the confocal microscopy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 318001 (2012)
Nonlinear Optics
Investigation of Quasi-Phase-Matching Frequency Doubling of 1560 nm Laser by Use of PPLN and PPKTP Crystals
Guo Shanlong, Han Yashuai, Wang Jie, Yang Baodong, He Jun, and Wang Junmin
The continuous-wave (CW) light obtained by the 1560 nm external-cavity diode laser (ECDL) is amplified to about 5 W by a erbium-doped fiber amplifier (EDFA). The periodically poled lithium niobate crystal and the periodically poled potassium titanium orde phosphate crystal are used to perform single-pass qusi-phase-macThe continuous-wave (CW) light obtained by the 1560 nm external-cavity diode laser (ECDL) is amplified to about 5 W by a erbium-doped fiber amplifier (EDFA). The periodically poled lithium niobate crystal and the periodically poled potassium titanium orde phosphate crystal are used to perform single-pass qusi-phase-mached frequency. The 780 nm laser power of about 336 mW and 210 mW, the frequency doubling efficiency about 7% and 4.4% are abtained. It shows that the good characteristic of single frequency output by monitoring the longitudinal mode of 780 nm laser. Additionally, the absorption spectra for Rb atom line D2 are scanned, and the tunable range of the 780 nm laser is more than 10 GHz. The ECDL is locked to 87Rb 5S1/2(Fg=2)-5P3/2(Fe=3) hyperfine transition via modulation-free polarization spectroscopy. Compared with frequency fluctuation of about 4 MHz for ECDL free running within 450 s, the residual frequency fluctuation can be squeezed below about 1.5 MHz after being locked..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 319001 (2012)
Optical Design and Fabrication
A Deformable Mirror with 9 Actuated Points for Low Order Aberration Correction-Design and Experiments
Chen Xindong, Zheng Ligong, Luo Xiao, and Zhang Xuejun
An effective aperture of 120 mm continuous face-sheet, discrete actuator deformable mirror (DM) is designed and experimentally tested. DM is aimed to correct defocus, astigmatism and coma, and the parameters of the DM are optimized, and it has nine actuated points and three fixed points. The fixed points are used to deAn effective aperture of 120 mm continuous face-sheet, discrete actuator deformable mirror (DM) is designed and experimentally tested. DM is aimed to correct defocus, astigmatism and coma, and the parameters of the DM are optimized, and it has nine actuated points and three fixed points. The fixed points are used to determine spatial position of the mirror and the actuated points are used to generate desired surface. Actuators are linear step motors with springs on the pushing end, which convert displacement to force. Test instrument used for DM is 4D dynamic interferometer. The test results show that the DM can generate defocus, astigmatism and coma with high accuracy, and it has a large dynamic correcting range..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322001 (2012)
Design Simulation and Optimization for the Flexible Displacement Support Structure Based on 1.8 m Lightweight Reflector
Zhong Xianyun, Fan Bin, Zeng Zhige, and Zhou Jiabin
Large-diameter lightweight mirrors with a flexible support structure can reduce the external force loads, inertia loads, heat loads and so on to ensure the quality of the optical imaging system. In order to eliminate the positioning error during polishing, testing and installation process, a novel support technology naLarge-diameter lightweight mirrors with a flexible support structure can reduce the external force loads, inertia loads, heat loads and so on to ensure the quality of the optical imaging system. In order to eliminate the positioning error during polishing, testing and installation process, a novel support technology named flexible displacement support model is used in CCAL polishing. Based on finite element analysis software Ansys, the greatest amount of tilt, the maximum principal stress and the deformation of 1.8 m lightweight reflector caused by CCAL polishing based on the flexible displacement support are analyzed, the simulation and optimization of the diameter and distance of the restriction pad are finished, and the deformation of 1.8 m lightweight reflector in different amounts of springs compression is simulated. Simulation results show that the stiffness of flexible support structure, amounts of tilt of reflector floor plate can meet the polishing condition, maximum principal stress intensity is much smaller than the yield stress of the primary mirror, and the deformation satisfies the processing requirements..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322002 (2012)
Design of a Low F-number Compact Athermalizing Infrared Optical System
Qu Hemeng, Zhang Xin, Wang Lingjie, and Zhang Jizhen
According to the requirements of good image quality, miniaturized dimension and high-temperature environmental adaptability in the applications of infrared search and track systems presently, a compact infrared catadioptric system structure is used, which base on the J-T cooler staring high-sensitivity focal plane arraAccording to the requirements of good image quality, miniaturized dimension and high-temperature environmental adaptability in the applications of infrared search and track systems presently, a compact infrared catadioptric system structure is used, which base on the J-T cooler staring high-sensitivity focal plane array infrared detector comprised of 320×320 elements, to design a low F-number and compact athermalizing infrared system optical system. The ratio of total length and focal length is 0.6. A passive optical athermalization design is used for infrared optical systems, which makes the system athermalize in the temperature range of -40 ℃～60 ℃. The stray radiation in the system is also analyzed and a scheme to suppress the stray radiation is given. The results show that the modulation transfer function (MTF) (17 lp/mm) of optical system in all field of view approaches the diffraction limit at different temperature, and 80% energy concentrates in 1 pixel. The optical system has many advantages, such as compact structure, small volume and so on . It can meet requirement of imaging infrared search and track..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322003 (2012)
Illumination Uniformity Optimization of Wide-Viewing-Field Optical System
Zhong Xing, Zhang Yuan, and Jin Guang
To increase the uniformity of image illumination of wide-viewing-field optical systems, influencing factors are analyzed theoretically. Idea of optimizing image illumination uniformity by contrast of axial rays′ section area and oblique rays′ section area is raised. Mathematic model is established in ideal optical systTo increase the uniformity of image illumination of wide-viewing-field optical systems, influencing factors are analyzed theoretically. Idea of optimizing image illumination uniformity by contrast of axial rays′ section area and oblique rays′ section area is raised. Mathematic model is established in ideal optical system. The law that ratio of rays section area changed with viewing-field angle influenced by central circular obscurations is acquired. Degeneration of modulation transfer function (MTF) caused by obscuration is analyzed. Optimization approach through dynamic data exchange (DDE) between software Zemax and Matlab is put forward. A focal length 56 mm, relative oparture 1/5.6, 2ω=80°air-survey camera lens is taken as an example to perform the optimization, and result shows its non-uniformity of image illumination decrease to 3.5% from 22.3% by adding a central obscuration on fifth surface, whose outer radius is 4.384 mm. The change of MTF is discussed in this example, and the MTF values with obscuration can satisfy the CCD imaging requirements..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322004 (2012)
Thermal and Structural Deformation of Projection Optics and Its Influence on Optical Imaging Performance for 22 nm Extreme Ultraviolet Lithography
Yang Guanghua, and Li Yanqiu
Extreme ultraviolet lithography (EUVL) is the next generation lithography for the semiconductor manufacturer to achieve 22 nm node and below. In the process of exposure, the 35%～40% incident power will be absorbed by multilayers of extreme ultrauiolet (EUV) optics, resulting in the thermal and structural deformation ofExtreme ultraviolet lithography (EUVL) is the next generation lithography for the semiconductor manufacturer to achieve 22 nm node and below. In the process of exposure, the 35%～40% incident power will be absorbed by multilayers of extreme ultrauiolet (EUV) optics, resulting in the thermal and structural deformation of the mirror, and consequently affecting the optical performance of the projection optics (PO). It is based on a six-mirror PO designed for EUVL at 22 nm technology generation with an image numerical aperture of 0.3. Finite element analysis (FEA) method is used for the deformation analysis of the six-mirror PO, and then the deformation is introduced to CODE V to evaluate its effect on the PO. The results show that the maximum temperature increase is 9.77 ℃, and the maximum deformation at clear aperture is 5.89 nm, with the beam power of 321 mW onto the wafer and wafer throughtput reaches 100 wafers per hour. While it is partial coherently illuminated (partial coherent factor 0.5), the distortions of 22 nm line and space is 6.956 nm, critical dimension (CD) error is 3.414%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322005 (2012)
Optical Design and Thermal Analysis for the Active-Focusing Aerial Camera Objective
Lan Gongpu, Wang Xuan, Liang Wei, Gao Xiaodong, and Ma Wenli
In the troposphere, the higher the altitude ascends, the lower the temperature is. To compensate the influence of the change of temperature upon the image quality, an active-focusing aerial camera objective is designed, for which f is 400 mm, field of view 2ω is 10°, F number is 8, wavelength range is 460～750 nm, In the troposphere, the higher the altitude ascends, the lower the temperature is. To compensate the influence of the change of temperature upon the image quality, an active-focusing aerial camera objective is designed, for which f is 400 mm, field of view 2ω is 10°, F number is 8, wavelength range is 460～750 nm, total track is 380 mm and back focal length BFL is 150 mm. This objective has perfect resolution, whose modulation transfer function fMT is no less than 0.52 at 70 lp/mm and the root mean square (RMS) diameter of the spot is 3.6 μm. A focusing group is equipped in this objective whose motion range is ±5 mm, and the 0.1 mm moving value is responsible for 0.026 mm in the image plane. The stationary thermal analysis and the temperature gradient emulation of the camera objective are presented subsequently. For the stationary thermal analysis, it is showed that after the active focusing, the aerial camera objective can obtain good image quality at the temperature range of -60 ℃～+60 ℃. For the temperature gradient emulation, each lens′ temperature gradient is set artificially which obtains the 20 ℃ axial and radial temperature gradients respectively; the result of the emulation shows that the objective can obtain good image quality at the 20 ℃ temperature gradient by active focusing..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322006 (2012)
Design Method of Optical System of Improved Czerny-Turner Imaging Spectrometer
Liu Jianpeng, Tang Yi, Huang Gang, Zhang Zhige, and Ni Guoqiang
Astigmatism is the main aberration that limits the spatial resolution of Czerny-Turner imaging spectrometer. Focal power is introduced to calculate astigmatism, and formulas are deduced to correct it. The method of computing the distance between grating and collimator is given, which is able to correct the aberration oAstigmatism is the main aberration that limits the spatial resolution of Czerny-Turner imaging spectrometer. Focal power is introduced to calculate astigmatism, and formulas are deduced to correct it. The method of computing the distance between grating and collimator is given, which is able to correct the aberration of the edge of field of view. The computing method of tilt angle of imaging plane, which is helpful to correct the aberration at all wavelengths. And an imaging spectrometer based on such structure working in 115~200 nm is designed, with f′=48 mm, F number is 5.0 and image size is 8 mm×7 mm. The designed imaging spectrometer can get spectral resolution δλ=0.22 nm and modulation transimission function (MTF) is 0.7 at all wavelengths and full field of view. The design method can be applied to other imaging spectrometers of different structures..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322007 (2012)
New Method for All Movable Zoom Lens Design
Cai Wei, Zhang Ying, Zhang Xin, Wu Yanxiong, and Zhang Jizhen
In order to get the simple computational formula for all movable zoom lens and reduce excessive dependence on designing experience of zoom lens, a new way to calculate optical-power distribution of zoom system is proposed. Taking the group spacing as initial parameter and the actions of components as independent variabIn order to get the simple computational formula for all movable zoom lens and reduce excessive dependence on designing experience of zoom lens, a new way to calculate optical-power distribution of zoom system is proposed. Taking the group spacing as initial parameter and the actions of components as independent variables, the corresponding optical-power distribution and actions of components which satisfy the constraint of group space is get. This method reduces the difficulty of optical-power distribution and it is more important it provides us with another way to find the new varifocal moving mode. After getting the power distribution, we also deduce a simple way to obtain actions of each component. In order to prove the feasibility of this method, a four movable component zoom lens is demonstrated and the calculation result agrees well with the optimized result..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 322008 (2012)
Optical Devices
Investigation of White Light Emitting Diode Based on Ce:YAG Single Crystal
Lu Shenzhou, Yang Qiuhong, Xu Feng, and Wang Yonggang
Ce:YAG single crystal for white light emitting diode (LED) is developed to replace conventional Ce:YAG phosphor powder. The effects of changing the Ce:YAG single crystal thickness and the driving voltage on the emission spectra, color coordinates, luminance, luminous efficacy and color temperature of white LED are inveCe:YAG single crystal for white light emitting diode (LED) is developed to replace conventional Ce:YAG phosphor powder. The effects of changing the Ce:YAG single crystal thickness and the driving voltage on the emission spectra, color coordinates, luminance, luminous efficacy and color temperature of white LED are investigated. Results show that the color coordinates and intensity ratio of blue and yellow-green light can be improved by adjusting the thickness of Ce:YAG single crystals. With the decrease of Ce:YAG single crystals′ thickness, the luminance, luminous efficacy and color temperature of white LED are increased. Pure white emission can be observed when the thickness of Ce:YAG single crystal is 0.6 mm, and its color coordinates are not varied with the change of driving voltage. All results show that Ce:YAG single crystal is a new material for new white LED devices..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 323001 (2012)
A New Method of Error Autocompensation for Ring Laser Gyroscope in Rotation-Modulated Strapdown Inertial Navigation System
Liu Jieyu, Yu Guoqiang, Yang Jianye, and Wang Lixin
The error autocompensation technique based on rotation-modulation is an effective method to improve the navigation accuracy of ring laser strapdown inertial navigation system. The error compensation method of ring laser gyroscope (RLG) in rotation-modulated strapdown inertial navigation system (RMSINS) is studied. The The error autocompensation technique based on rotation-modulation is an effective method to improve the navigation accuracy of ring laser strapdown inertial navigation system. The error compensation method of ring laser gyroscope (RLG) in rotation-modulated strapdown inertial navigation system (RMSINS) is studied. The error propagation equations of RLG in RMSINS are built, then the rotating error effect and the error propagation characteristics are analyzed through modeling. Based on this, the object function of modulation schemes is deduced and the modulation scheme under Indexing is arranged effectively. Then an improved sixteen-sequence two-axis indexing scheme is proposed to compensate the RLG′s constant drift error, scale factor error, fixing error, and the position error produced by speed error accumulating based on the dynamic error function of two-axis rotating speed. The simulation results show the effectiveness which lays a sound foundation for actual application of RMSINS..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 323002 (2012)
Spatial Coherence of High-Power Single-Color LED
Lin Huichuan, Tao Hua, He Meng, Pu Jixiong, and Rao Lianzhou
Based on the van Cittert-Zernike theorem, we study the spatial coherence distribution of the light beam, which radiated from the high-power single-color light-emitting diodes (LED) after propagation theoretically. The theoretical calculations show that, the spectral coherence of the light beams which radiated from the Based on the van Cittert-Zernike theorem, we study the spatial coherence distribution of the light beam, which radiated from the high-power single-color light-emitting diodes (LED) after propagation theoretically. The theoretical calculations show that, the spectral coherence of the light beams which radiated from the non-coherent LED source changed into partially coherent after propagation. Moreover, the spatial coherence of the light beams is related to its chip architecture of the LED. By double-slit interference we measure the spatial coherence of the light beams experimentally. And the visibility of the interference fringes show that the light beams from the non-coherent LED source change into partially coherent after propagation. In addition, the measurement of the visibility by use of adjustable double-slit reveal that, the emitting area of the LED determines the spatial coherence of the light beams from LED source. The theoretical result of the spatial coherence is almost consistent with the experimental measurement..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 323003 (2012)
Parameter Estimation of Gaussian Gray Diffusion Model of Static Image Spot
Wang Haiyong, Zhou Wenrui, Lin Haoyu, and Wang Xinlong
In order to estimate the parameters in Gaussian gray diffusion model, experiments with collimator are carried out while the parameter calibration algorithm is proposed. Equations which take the Gaussian diffusion radius and the deviation values of the centroid coordinate as variables are established and solved, furtherIn order to estimate the parameters in Gaussian gray diffusion model, experiments with collimator are carried out while the parameter calibration algorithm is proposed. Equations which take the Gaussian diffusion radius and the deviation values of the centroid coordinate as variables are established and solved, furthermore, the energy-gray coefficient is obtained. Then, series of photos are taken under the same condition in three different orientations, and parameters whose mean values are taken as their estimates are calculated respectively using these gray data of photos. Finally, all the estimated parameters are put into the simulating model, and a model-generated star image spot is therefore got, the similarity between which and real shot ones is calculated in three different windows under the condition that noise is bound to exist. The similarity is a value of more than 0.97 within the window of 3 pixel×3 pixel, more than 0.98 for a 5 pixel×5 pixel, and more than 0.98 for a 7 pixel×7 pixel. The experimental results show that the solution formulas about σ, A and the deviation Δx and Δy are right..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 323004 (2012)
Exploring the Feasibility and Approach for Unfilmed-Microchannel-Plate Based Third Generation Image Intensifiers
Pan Jingsheng, Lü Jingwen, Li Yanhong, and Zhou Jianxun
Gallium arsenic (GaAs) photocathode demonstrates an excellent quantum efficiency superior to multialkali photocathode. Because of an ion barrier film existed on the input face of microchannel plate (MCP), gen.3 image intensifiers tubes (IIT), even the thin film gen.3 IIT, have not shown evident advantage on the main paGallium arsenic (GaAs) photocathode demonstrates an excellent quantum efficiency superior to multialkali photocathode. Because of an ion barrier film existed on the input face of microchannel plate (MCP), gen.3 image intensifiers tubes (IIT), even the thin film gen.3 IIT, have not shown evident advantage on the main parameters of singal-to-noise ratio and resolution under standard test condition over super gen.2 IIT which updated simultaneously. The effective availability of photocathode quantum efficiency of IIT are evaluated by introducing a conception of MCP noise figure. Necessity of the realization of unfilmed gen.3 IIT is emphasized. The problem remains in the currently unfilmed MCP gen.3 IIT are indicated. The methods to improve MCP endurance capability of electron scrubbing resistance degassing treatment and further reduction of the number of poison species which contain in MCP substrate are researched, while the feasibility and technology approach for high reliability and high performance unfilmed MCP gen.3 IIT are pointed out..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 323005 (2012)
Optics at Surfaces
Relation Between the Multicrystalline Silicon Surface Structure and the Pit-Trap Effect
Wang Kunxia, Feng Shimeng, Xu Huatian, Tian Jiatong, Yang Shuquan, Huang Jianhua, and Pei Jun
An optimization etching model of the traps surface is proposed for the multicrystalline silicon surfaces. Based on uncertainty principle, the dependence of the photon scattering direction on the size of salient point on the internal surface of trap-pit is studied. The relationship between the topography of pit and the An optimization etching model of the traps surface is proposed for the multicrystalline silicon surfaces. Based on uncertainty principle, the dependence of the photon scattering direction on the size of salient point on the internal surface of trap-pit is studied. The relationship between the topography of pit and the reflectivity is deduced using Fourier transformation. The theoretical analysis results indicate that the U-trap with the internal surface full of salient points has low reflectivity compared with V-trap with the internal surface full of salient points. However, the reflectivity of U-trap with the smooth internal surface is higher than that of the V-trap. The topography of multicrystalline silicon surface in different models textured with alkaline solution are observed by scanning electron microscope. It is found that \[100\], \[111\] and \[110\] planes is covered with canyon-structures, distorted U-trap and hybrid structures, respectively. The reflectances of different crystallographic planes are measured, showing that the U-trap′s reflectance is the smallest. And it proves the proposed model..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 324001 (2012)
Quantum Optics
Optical Quantum Random Number Generator Based on the Time Randomness of Single-Photon Pulse
Yan Qiurong, Zhao Baosheng, Liu Yongan, and Sheng Lizhi
An optical quantum random number generator based on the time randomness of single-photon pulse is proposed. A constant-intensity light source attenuating into single-photon state and a single photon detector are used to generate single-photon random pulses. The random bits are extracted by continuously comparing the tiAn optical quantum random number generator based on the time randomness of single-photon pulse is proposed. A constant-intensity light source attenuating into single-photon state and a single photon detector are used to generate single-photon random pulses. The random bits are extracted by continuously comparing the time intervals between two adjacent pulses in the single-photon random pulses sequence. A random number generation rate of more than 10 M bit/s is obtained by designing high-speed single-photon detector based on micro-channel plate and field programmable gate arry (FPGA) based random bit extraction circuit. In order to reduce the correlation coefficient of random bit sequence, measurement accuracy of the time interval is improved by using a constant fraction discriminator and a frequency-multiplied counting clock. Correlation coefficient of the random bit sequence is less than 0.001, when the random bit generation rate is less than 10 k bit/s. The random bit sequences are tested by random number test program ENT and DIEHARD. The test results show that random bit sequences have good randomness, do not require post-processing and fully meet the standards of true random numbers..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 327001 (2012)
Control of the Entanglement Between the Two Atoms Interacting with a Fock State Field
Liao Qinghong, and Liu Ye
The dynamics of entanglement of two two-level atoms initially in excited state interacting with a Fock state field is examined by means of concurrence. The effects of photon number, atom-cavity detuning and manipulation of the atom on the time evolution of concurrence are investigated. The results show that the phenomeThe dynamics of entanglement of two two-level atoms initially in excited state interacting with a Fock state field is examined by means of concurrence. The effects of photon number, atom-cavity detuning and manipulation of the atom on the time evolution of concurrence are investigated. The results show that the phenomenon of sudden birth of entanglement between two atoms occurs in the absence of the manipulation of the atom. Moreover, the threshold time for the creation of entanglement and the maximum of the entanglement can be controlled by the photon number and the atom-cavity detuning. The entanglement between two atoms can be created immediately as time develops in the presence of manipulation of the atom. The atom-atom entanglement can be manipulated by the application of the classical field..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 327002 (2012)
Spectroscopy
Optimization of Frequency Modulation Spectral Lineshape Influenced by the Residual Amplitude Modulation Based on the Low Frequency Control of Electro-Optic Modulator
Zhang Yongzhi, Li Zhixin, Yan Xiaojuan, Wang Le, Hu Zhiyu, Ma Weiguang, Zhang Lei, Yin Wangbao, and Jia Suotang
The residual amplitude modulation (RAM) induced by the polarized state changes of laser light in frequency modulation (FM) spectroscopy limits its application in the field of trace gas detection. The process is analyzed theoretically. The expression of the FM spectroscopic lineshape which contains the RAM is obtained. The residual amplitude modulation (RAM) induced by the polarized state changes of laser light in frequency modulation (FM) spectroscopy limits its application in the field of trace gas detection. The process is analyzed theoretically. The expression of the FM spectroscopic lineshape which contains the RAM is obtained. The expression of FM spectral lineshape is given when the RAM is restrained by N.C.Wong and J.L.Hall (W-H) method. The spectrum profile which contains the RAM is got by the measurement of the acetylene gases in the experiment. Then the W-H method is used to restrain the RAM and the optimized spectral lineshape is obtained. Finally, the results of the measured lineshape are fitted based on the theoretical method and the value difference between the two signals is less than 4% compared with the signal peak value..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 330001 (2012)
Experimental Verification for Line by Line Prediction Model of Gas Absorption
Mei Fei, Jiang Yong, Chen Shiguo, and Fang Haobai
A high resolution line-by-line model to calculate the molecular gas spectra is developed. With the model, the absorption coefficients can be calculated using molecular data from the up-to-date spectroscopic databanks (HITRAN2008/HITEMP2010). The model can choose the proper databank according to the temperature conditioA high resolution line-by-line model to calculate the molecular gas spectra is developed. With the model, the absorption coefficients can be calculated using molecular data from the up-to-date spectroscopic databanks (HITRAN2008/HITEMP2010). The model can choose the proper databank according to the temperature condition. Thus, it can calculate the absorption coefficient on high temperature and room temperature. The sampling interval is set constant. The choice of interval depends on the factor that the resolution must be high enough to resolve the typical gas line fully. The model uses equal line wing cutoff to take account of contribution of the most important spectra lines. The total internal partition function for the spectra lines is calculated using the tertiary polynomial expression which is fitted by Gamache. The spectra line profile is determined according to the gas temperature and pressure. Finally, the model is employed to calculate the spectral transmissivity of CO2 at various temperatures, concentrations, and path lengths for the 4.3 μm and 2.7 μm bands. Then the line-by-line calculated data is used to calculate narrow band transmissivity at the measured resolution, accounting for instrument broadening by the FTIR. A comparison between the narrow band and measured transmissivity showed a good agreement among a wide temperature area..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 330002 (2012)
Hyper-Spectrum Classification Based on Sparse Representation Model and Auto-Regressive Model
Song Lin, Cheng Yongmei, and Zhao Yongqiang
A novel classification approach based on sparse representation model and auto-regressive model is presented to deal with spectral and spatial information underutilization effectively for hyper-spectrum classification. The combination dictionary is designed using sparse representation model and auto-regressive model. SpA novel classification approach based on sparse representation model and auto-regressive model is presented to deal with spectral and spatial information underutilization effectively for hyper-spectrum classification. The combination dictionary is designed using sparse representation model and auto-regressive model. Sparse representation model is used to represent every spectral vector as sparse linear combination of the training samples on spectral dimension; auto-regressive model is added to constrain every spectral vector by its eight neighborhoods on spatial dimension. A new dictionary is constructed for every class to reduce the computation and reconstruction error. At last, the sparse problem is recovered by solving a constrained optimization of minimum reconstruction error and neighboring relativity. The classification of hyper-spectral image is determined by computing the minimum reconstruction error of testing samples and training samples. Simulation results show that the method improves the classification accuracy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 3, 330003 (2012)
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