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NUCLEAR TECHNIQUES
2018 Vol.47 Issue.7
Published 2018-07-25

Contents
Diffraction and gratings
Image processing
Lasers and laser optics
Machine vision
Optical design and fabrication
Instrumentation, measurement and metrology
Microscopy
Geometric Optics
Optical devices
Scattering
Materials
Atmospheric and oceanic optics
      
Contents
2018 Vol. 47 (7): 0-0 [Abstract] ( 16 ) PDF (276 KB)   ( 21 )
Diffraction and Gratings
Influence of Ag Nanowires on Optical Absorption of Different Grating Structures under Fixed Volume Ratio
CHEN Ke, FANG Xu, ZHENG Hong-mei, WU Rui, WANG Yuan-yuan

In order to study the influence of Ag nanowires on the light absorption efficiency of crystalline silicon thin film solar cells, a kind of crystalline silicon thin film solar cell structure with triangular grating and rectangular grating at fixed volume ratio was designed. At the Ag-Si junction of the two structures, a circular and rectangular Ag nanowire array were added respectively. The absorption spectra of these two structures and the control group were simulated by finite difference time-domain method. The optimal height, nanowire cross-sectional area, and distribution density of the two grating structures were obtained by sweeps function of finite difference time-domain method software, and the light absorption efficiency of wavelength region of 300~1 100 nm was calculated under the optimal conditions. The absorption enhancement mechanism of the nanowire model in the long wavelength band was obtained by analyzing the light absorption enhancement spectra and the electromagnetic field intensity distribution. The results showed that the two structures with Ag nanowires had better light capture and absorption than the two control groups. Moreover, the absorption efficiency of Ag nanowires in the rectangular grating model is improved more significantly than the triangular grating model, which can provide reference for the design of structural parameters of new solar cells.

2018 Vol. 47 (7): 705001-0705001 [Abstract] ( 121 ) PDF (7018 KB)   ( 130 )
Influence of UV-exposure on the Diffraction Characteristics of Volume Bragg Grating
XIONG Bao-xing, ZHANG Gui-ju, ZOU Kuai-sheng

Volume Bragg grating with the grating period 2.1 μm was recorded in the photo-thermo-refractive glass with laser amplitude-split interference and "two-step" heat treatment process. The diffraction efficiency and angular selectivity of Bragg grating are very much affected by the laser dosage. The He-Cd laser with UV wavelength 325 nm is used. With the increase of UV dosage, the diffraction efficiency increases constantly. When the UV dosage increases to 0.6 J/m2, the diffraction efficiency of the grating reaches the maximum value of 80.02%., The efficiency will decrease as the UV dosage increases more than 0.6 J/m2 and remain a stable value as the dosage reaches at 1.5 J/m2, while the grating absorption change is less than 5%. The grating angle selectivity remains stable as the dosage changes. The experiment results show that the increase of UV dosage enhances the silver containing particles absorption at work wavelength 532 nm. The transmitted diffraction light was attenuated and the diffraction efficiency decreased.

2018 Vol. 47 (7): 705002-0705002 [Abstract] ( 74 ) PDF (2633 KB)   ( 101 )
Image processing
Non-casual Real-time RXD Detection for Hyperspectral Imagery Based on Sliding Array
ZHAO Liao-ying, LIN Wei-jun, WANG Yu-lei, LI Xiao-run

To reduce the storage and transmission burden of massive hyperspectral data as well as keep detecting the anomaly targets accurately and rapidly, a novel non-causal real-time anomaly detection algorithm based on sliding array window is proposed. During receiving the data pixel-by-pixel, the array window slides and determines the local background pixels; and according to the Woodbury lemma, the computation of the matrix inverse of local background can be replaced by the vector multiplication and matrix additions equivalently, then the anomaly pixel in the center of the sliding array window would be detected when receiving the data pixel-by-pixel. The experiments on synthetic and real-world hyperspectral images demonstrate that, compared with several existing real-time detection methods, the proposed method can improve the performance of detection accuracy or computational efficiency. Compared with the non-real-time sliding array RXD anomaly detector, the proposed algorithm has a lower time complexity, and the speedup ratio is nearly 26 times when processing an image with 200×200 pixels and 189 bands. Experimental results verified that the proposed algorithm could maintain the detection accuracy as well as meet the real-time requirements of low computational complexity and low storage space.

2018 Vol. 47 (7): 710001-0710001 [Abstract] ( 42 ) PDF (4327 KB)   ( 20 )
Nonuniformity Correction Method Based on Statistical Consistency of Adjacent Pixels
LIU Ya-mei

To correct the nonuniformity of long-wave infrareddetectors, a nonuniformity correction method based on statistical consistency of adjacent pixels is proposed. First, the model of radiance nonuniformity is introduced. Then, the ratio between adjacent pixels is estimated with a mean operator, and the correction coefficients are calculated iteratively. Finally, a principle prototype is set up to grab different scenes. Experimental results demonstrate that the proposed method can decrease the roughness of the corrected images from 1.27×10-2 to 1.13×10-2, and the local standard deviation from 10.5 to 3.5, compared with the calibration-based method. The proposed method can reduce nonuniformity noise of infrared detectors effectively.

2018 Vol. 47 (7): 710002-0710002 [Abstract] ( 28 ) PDF (3316 KB)   ( 39 )
Lasers and laser optics
Effects of Ambient Air Pressure on Femtosecond Laser Induced Periodic Ripple Structure on Chromium Films
LIU Qi, ZHANG Nan, YANG Jian-jun

The formation of one dimensional periodic subwavelength (~250 nm) ripple structures on the surface of Si-based Cr film was investigated by irradiation of blue femtosecond laser pulses (1 kHz, 50 fs, 400 nm) under different ambient air pressures of 105 Pa (or 1atm) and 10-3 Pa. The effects of the experimental parameters such as the incident laser energy fluence, the sample scanning speed and the film thickness, on the development of the surface ripple structures were compared. The results demonstrate that the quality of the surface structures can be effectively improved either by the low air pressure of 10-3 Pa or by reducing the thickness of Cr film (100~25 nm), however, the uneven ablation may be appeared when the Cr film is too thin (≤ 25 nm). Moreover, with decreasing the laser energy fluence or increasing the scanning speed, the spatial period of the ripple structures tends to become smaller, accompanied by the nanowires growth inside the grooves of the ripple structures.

2018 Vol. 47 (7): 714001-0714001 [Abstract] ( 38 ) PDF (4591 KB)   ( 63 )
Experimental Investigation on Nonlinear Dynamics of a Multi-transverse Mode 1 550 nm Vertical-cavity Surface-emitting Laser Subject to Parallel Optical Injection
YANG Wen-yan, XIA Guang-qiong, HOU Yu-shuang, JIANG Zai-fu, DENG Tao, WU Zheng-mao

The nonlinear dynamics of a multi-transverse mode 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL) under parallel optical injection is experimentally investigated. For a free-running 1550 nm-VCSEL biased at a suitable current, the fundamental and high-order modes can oscillate simultaneously and dominantly operate at the Y Linear Polarizations (Y-LPs). After introducing a Continuous Wave (CW) injection with the polarized direction along Y-LP of the free-running 1 550 nm-VCSEL (named as parallel optical injection), two different scenarios have been investigated experimentally, namely the frequency of injected CW (νinj) is close to the fundamental transverse mode frequency (νfy) (the frequency detuning is defined as Δνf=νinj-νfy) or the high-order transverse mode frequency (νfy) (the frequency detuning is defined as Δνh=νinj-νhy). For the first case, the results show that, during the process of continuously increasing injection power (Pinj), the fundamental mode undergoes diverse dynamical states, but less dynamical states are observed for the high-order mode. With the increase of Pinj, the output power of the high-order mode is decreased gradually. For a strong enough Pinj, the high-order mode can be totally suppressed and therefore the laser operates at single transverse mode, i. e. the mode selection for the fundamental mode achieves. With the increase of Δνf, the minimal injection power required for achieving the fundamental transverse mode selection (Pinj,min) decreases firstly, after reaches a minimum, and then increases. The larger the biased current, the larger the value of Pinj,min. For the second case, during the process of increasing Pinj, both high-order mode and fundamental transverse mode undergo multiple dynamical states. However, the phenomena that the fundamental transverse mode is suppressed has not been observed, i. e. the mode selection for high-order mode cannot be realized.

2018 Vol. 47 (7): 714002-0714002 [Abstract] ( 64 ) PDF (4058 KB)   ( 79 )
Machine Vision
Infrared Ultra-wide Angle Image Distortion Centre Calibration Method Based on High Odd-order Polynomial Model
LIU Bing-qi, CHEN Yi-chao, HUANG Fu-yu

Due to the image distortion of the infrared ultra-wide angle system is large, the diffraction is obvious and the precision of traditional calibration method is not high, this article puts forward a kind of infrared ultra-wide angle image distortion centre calibration method based on the high odd-order polynomial model. The calibration method is designed by analyzing the radial and the tangential magnification of the small circular target. The ellipse equation is used to fit the target image, then two dimensional Gauss surface fitting is based on the ratio of the elliptical long and short axis as the objective function. Finally, the center of Gauss surface is regarded as the centre of distortion. The experimental results show that the calibration accuracy of the proposed method are 0.77 pixels and 1.02 pixels respectively. The distorted image is corrected by this calibration result. In the corrected image, the maximum root-mean-square-error of the line is 1.56 pixels. The experiment verifies the accuracy of the proposed infrared ultra-wide angle image center calibration method, which meets the requirements of the infrared ultra-wide angle image distortion center calibration.

2018 Vol. 47 (7): 715001-0715001 [Abstract] ( 36 ) PDF (2527 KB)   ( 86 )
Defocus Camera Calibration Based on Sinusoidal Phase Coding
YANG Hao, CAI Ning, LIN Bin, CAO Xiang-qun

The influence of the defocus state of the optical system on the phase of structured light based on sine grating, abbreviated as sinusoidal structured light, was analyzed. Based on the property that the sinusoidal structured light phase is independent of the camera's focusing state, a method of calibrating the camera in the defocus state using a phase-shifted sinusoidal-structured-light-encoded display panel is proposed. The Floyd-Steinberg Dithering algorithm is used to eliminate the structured light phase calculation errors caused by the gamma conversion of the display panel. This method makes the accurate extraction of the feature points of the calibration object under the defocus state come true. The calibration result has a reprojection error of 0.17 pixels. The calibration error of the camera focal length is within 0.39%. The calibration accuracy was improved compared to traditional methods. A solution for the calibration of cameras with a special imaging range was provided.

2018 Vol. 47 (7): 715002-0715002 [Abstract] ( 21 ) PDF (4275 KB)   ( 43 )
Optical Design and Fabrication
Design of a Single Lens Laser Triangulation Probe Based on PSD
ZHANG Xin-ting, KANG Lei, AN Zhi-yong, WANG Run-zhi

Based on the traditional direct laser triangulation method, a single lens laser triangulation probe based on position sensitive detector was designed. A beam splitter is introduced, and the focus lens and the imaging lens are merged into one. In the spatial layout, making the beam splitter, detector and condensing lens are coaxial. The structure of the system is more compact, and the Scheimpflug condition satisfying the structure is derived. The optical system is simulated by Zemax optical design software, the focal length of the system is 20 mm, the diameter of the pupil is 4 mm, and the total length is 20.5 mm, so that the miniaturization of the measurement system can be realized. At the same time, the nonlinear correction of the position sensitive detector and the related signal processing are carried out to ensure a greater working range on the premise of higher measurement accuracy, and make the system and improve the adaptability of the system to the measurement environment. It can be widely applied to industrial real-time online detection and other fields.

2018 Vol. 47 (7): 722001-0722001 [Abstract] ( 40 ) PDF (3435 KB)   ( 40 )
Gravity and Support Error Separation of 1.2 m Lightweight Space Mirror
ZHANG Long, YE Lu, ZHANG Jin-ping, ZHENG Lie-hua

The test result of space mirror figure in the ground environment is mainly composed of the surface processing residual and the distortion caused by gravity and support. In order to realize the gravity-support distortion separation of the 1.2 m lightweight space reflector, by testing mirror with equal gradient support forces, the relationship between mirror figure distortion and the change of support forces is obtained from the mirror mechanical response, which can be used as a basis for judging the result of finite element simulation and optimizing finite element model. After removing the mirror figure distortion calculated with the corrected model from the mirror test result, the surface processing residual is obtained. The research shows that the differece of mirror distortion change caused by 100 N supporting force change between the result calculated with the corrected model and the test result is ≤ 0.001λ, without the effects of gravity and support, the surface processing residual of space mirror with test result rms 1/30λ is better than 1/40λ. This result can not only guide the high precision surface polishing, but also improving the alignment precision of final system.

2018 Vol. 47 (7): 722002-0722002 [Abstract] ( 29 ) PDF (1917 KB)   ( 32 )
Optimum Design and Experiment Verification of Space Coaxial Reflective Secondary Mirror Support Structure
SUN Yi, LI Fu, YANG Jian-feng, QIAN Chong-sen

A sub-mirror support optimization model based on the outer envelope of the traditional secondary mirror support structure was established, according to the characteristics of the traditional coaxial reflective secondary mirror support structure. The variable density topology optimization method was used to optimize the model. According to the topology optimization results, a coaxial reflective secondary mirror support structure with an occlusion ratio of 0.085 was designed. The finite element simulation results show that the basic frequency and structural stiffness of the coaxial reflective secondary mirror support structure are significantly improved compared with the traditional three-wing and four-wing structures in the case of the same structure shielding ratio and mass. The optimized secondary mirror support structure was processed and a random vibration test was conducted. The test results show that the optimized basic frequency of the secondary mirror support structure is 470 Hz, the finite element simulation result is 477 Hz, and the relative error is within 2%, which verifies the reliability and authenticity of the finite element calculation model. The secondary mirror support structure is suitable for use in a coaxial reflective optical system that requires a lower mask ratio and higher stiffness.

2018 Vol. 47 (7): 722003-0722003 [Abstract] ( 44 ) PDF (4239 KB)   ( 37 )
Instrumentation, measurement and metrology
Photocatalytical Poison Gas Filter Based on Nano-TiO2 Mesoporous Silica Composite
MIAO Jing, ZENG Fan-zhe, GUAN Lei, WU Chun-xiao, HAN Sha-sha, HE Zheng-quan, KONG De-peng, WANG Li-li

A composite method of mesoporous silicon and nano-TiO2 were reported, then a nano-TiO2-mesoporous-silica composite were fabricated, which is of high adsorption and high photocatalytic activity. On this basis, a new type of photocatalytic gas filter was constructed,by using UV LED with 365 nm wavelength as light source, custom made semi-leakage optical polymer fiber as light guide medium. Experimental results show that it has a capacity of adsorbing formaldehyde of more than 3 mg on the filter with 350 g composite photocatalyst loading, and LED light power of 540 mW. After the filter is adsorption saturated, the formaldehyde gas flow rate is 2 L/min, the inlet concentration is 0.7 mg/m3, the rate of real-time decomposition of formaldehyde reaches 72 μg/h and the formaldehyde concentration in the output gas drops to 0.09 mg/m3, which is lower than the safety threshold of indoor formaldehyde concentration in national sanitary standards. Adsorption characteristics of the composite photocatalyst provides sufficient reaction time for photocatalytic decomposition, which helps improve the photocatalytic decomposition efficiency, long-term cycle work, and it is expected to be used for home air purification, or even replace the existing activated carbon gas filter, and be used as a long-term gas masks and other devices.

2018 Vol. 47 (7): 712001-0712001 [Abstract] ( 52 ) PDF (2055 KB)   ( 57 )
Estimation of Zernike Coefficients for Any Wavelength Transmitted Wavefront at Defocus Position
ZHANG Qi-yuan, HAN Sen, TANG Shou-hong, WANG Quan-zhao, JIANG Zhi-hua

Based on Zernike polynomials fitting wavefront, an algorithm of calculating Zernike coefficients for any wavelength transmitted wavefront at defocus position was put foward. The method compensates the change of Zernike coefficients of defocus distance based on Zernike coefficients at focus position. Using an achromatic system, the working position was optimized according to the wavelengths and weights, and the defocusing amount between focus position and working position was calculated, and the any wavelength wavefront Zernike coefficients at working position was verified by the algorithm. The result showed that the proposed algorithm is effective for calculating Zernike coefficients related to position, compared with using Conrady-Zernike formula in working position, the absolute error of Z1 decreased from 6.78 to 1.41, and the absolute error of Z4 decreased from 6.83 to 1.45.

2018 Vol. 47 (7): 712002-0712002 [Abstract] ( 45 ) PDF (2609 KB)   ( 80 )
Random Error Compensation Technology of MEMS Gyroscope Based on Time-varying ARMA Model
SONG Jin-long, SHI Zhi-yong, WANG Lü-hua, WANG Hai-liang

In order to improve the measurement accuracy of Micro Electro Mechanical System (MEMS) gyroscope, a time varying Auto-Regressive and Moving Average (ARMA) Model compensation method based on forgetting factor recursive least squares estimation was proposed. According to the measured MEMS gyro random drift signal without trend item, the stability was analyzed by the subsection test and the time varying ARMA was built with the suitable basis function and subspace dimension. The model parameters were estimated with the Forgetting Factor Recursive Least Square (FFRLS) method by setting forgetting factor to make it possible that the model parameters can reflect the dynamic change of the signal. For the time varying parameters with slight fluctuation, the 5 order polynomial was used to fit the parameters of the time-varying model, and an analytical method was proposed to optimize the parameters, so as to establish the optimal random drift model. And the modeling results were applied to Kalman filter for random drift compensation. The compensation results of the proposed method were compared with the compensation results of the time invariant ARMA modeling compensation method. The comparison results indicated that the variance of the signal with the proposed method compensation is nearly 40% reduced by the variance of the signal with the time invariant ARMA model compensation. So the compensation precision of MEMS gyro random drift was improved effectively.

2018 Vol. 47 (7): 712003-0712003 [Abstract] ( 12 ) PDF (2759 KB)   ( 21 )
Static Analysis and Modal Analysis of Planar Solar Concentrator
LIU Xin-ran, ZHANG Ning, XU Xi-ping, YIN Peng

In order to solve the problem of the drop of the condenser efficiency caused by the non-uniform force of the flat panel solar concentrator, an assembly method using nine array lenses as the condenser module was proposed. The air gap between the condenser module array and the optical waveguide board was set to 2 mm. Linear static analysis and modal analysis of flat solar concentrators were performed using ANSYS software. The set wind speed was 18 m/s, which was higher than the index level of 14 m/s, and the modal analysis fundamental frequency of the concentrator was 0.038 s. It is not necessary to take into account the dynamic influence conditions for the structural rigidity. The displacement of the concentrator and the optical waveguide plate structure under the condition of extreme static wind load and the modal coefficients of the first six orders in the corresponding case were discussed. The results show that the maximum displacement of the air gap between the concentrator and the optical waveguide plate structure is 0.049 mm, meeting the accuracy requirement. In the five kinds of the angle condition, the difference between the front 6 modes modal shape prestressed and processing mode shape is within 1%, and the corresponding shape patterns are similar. It is proved that the wind load has no effect on the mode shape.

2018 Vol. 47 (7): 712004-0712004 [Abstract] ( 21 ) PDF (5527 KB)   ( 59 )
Microscopy
Experimental Study on Micro Quantitative Phase Imaging by Quadriwave Shearing Interferometry
CUI Bo-chuan, WANG Jian-li, YAO Kai-nan, CHEN Tao

A micro quantitative phase imaging method based on quadriwave shearing interferometry is proposed. A chessboard phase grating is used to get the interferogram of biological samples, and the phase information is obtained by the fast Fourier transform method. A pack of wavefront produced by the micro-electromechanical systems is measured, and the ZYGO interferometer is used for comparision. The error of phase measurement is not more than 3%, which verifies phase detection accuracy of the quadriwave shearing interferometer. A quantitative phase imaging system based on the quadriwave shearing interferometry is established, and a clear quantitative phase image is obtained from murine hepatoma cell. The experimental results show that the system based on the quadriwave shearing interferometry can achieve high-precision quantitative phase imaging, and is suitable for phase imaging of biological living cells.

2018 Vol. 47 (7): 718001-0718001 [Abstract] ( 18 ) PDF (2563 KB)   ( 43 )
3D Trap Stiffness Measurement of Holographic Tweezers Based on Vision Theory and Hydrodynamic Method
HE Wei, LI Jing

In order to test the capture ability of holographic optical tweezers, an optical measurement system based on vision theory was used to measure the 3D trap stiffness of holographic optical tweezers. In the optical system, two symmetrically distributed light sources irradiated the sample cell to form two images. The 3D positions of the microspheres captured by the holographic optical tweezers were obtained by tracking the displacements of their images. Combined with hydrodynamic method, the trap stiffness of the single and double optical traps was measured. The experimental results show that in a single optical trap, there is little difference between X and Y horizontal trap stiffness, and the axial trap stiffness falls in the range of 1/3 to 1/4 of the horizontal direction; in double optical traps, the three-dimensional stiffness of the optical trap near the optical axis is larger than that an a far distance, which demonstrates that the closer to the diffraction center, the higher the diffraction efficiency of light, and the stronger the capture ability of the optical trap.

2018 Vol. 47 (7): 718002-0718002 [Abstract] ( 57 ) PDF (1840 KB)   ( 89 )
Geometric Optics
Propagation and Polarization Characteristics of the Radially Polarized High-order Bessel-Gaussian Vortex Beams
LIU Yong-xin, ZHANG Kai-ning, PU Ji-xiong

The intensity distribution and polarization characteristics of the radially polarized high-order Bessel-Gaussian vortex beams propagating in free space were studied theoretically and experimentally. Through numerical calculation, with transmission distance increasing, the intensity distribution remains unchanged in the diffraction free area. For a zero order beam, the polarization state remains the same. But for a higher order light beam, the polarization state changes, and the initial radial polarization gradually changes into the hybrid polarization state including elliptical polarization and linear polarization. In the experiment, a radially polarized high-order Bessel -Gaussian vortex beam is produced by using the radial polarization converter, vortex phase plate and axicon element. The light intensity distributions of the beams passing through different polarizers are detected. By comparing the experimental results with the theoretical results, it is found that they are basically consistent. The study also provides a method to produce the hybrid polarized vector beams.

2018 Vol. 47 (7): 708001-0708001 [Abstract] ( 75 ) PDF (3849 KB)   ( 132 )
Construction and Optimization of the Complementary Beam of Bessel Beam
JIA Hao, YU Xiang-hua, YANG Yan-long, ZHOU Xing, YAN Shao-hui, LIU Chao, LEI Ming, YAO Bao-li

The idea of propagation-invariant Complementary Beam (CB) to Bessel beam was proposed. Based on the Huygens-Fresnel principle and the superposition of coherent light field, the general form of CB's spectrum is suggested. The phase distribution of complex amplitude spectrum is optimized with the aid of genetic algorithm, in doing so the scanning complementary beam light-sheet enables to approximate the side lobes of Bessel light-sheet to the utmost. Thus, the substraction of two scans can eliminate the influence of the side lobes to produce a large FOV, homogeneous and thin light-sheet. The employment of the complementary beam into light-sheet fluorescence microscopy is a promising method to reduce the background signal as well as enhance the imaging quality.

2018 Vol. 47 (7): 708002-0708002 [Abstract] ( 36 ) PDF (2573 KB)   ( 48 )
Generation Theory and Experimental Study of Two Stage Non-diffracting Beam
YANG Gui-yang, MA Guo-lu, ZENG Guo-ying

In order to complete the transmission and transformation theory of multilevel non-diffracting beam and to expend the application range of two stage non-diffracting beam, the light field distribution of two stage non-diffracting beam was analyzed in detail on the basis of the axicon method and Fresnel diffraction theory. Based on the axicon method, an experimental platform for generating two stage non-diffraction beams is constructed. The cross section spots and their light intensity distributions transmitted along the optical axis at different distances are obtained. The influence of different incidence angles of parallel beams on the propagation and transformation of non-diffracting beams is investigated. Experimental results show that the two stage non-diffracting diffraction light field is composed of four regions, in the interference overlap region, the light intensity is the superposition coupling of the diffraction fields of the first and second axicons, the rest of the region remain the propagation characteristics of the single stage non-diffracting beam. The light intensity is influenced by the incident aperture and the bottom angle of the axicon lens. The rupture degree of the spot is positively correlated with the inclination of parallel beam. In this paper, the spatial propagation characteristics, the intensity distribution characteristics and the influence factors of the light intensity are analyzed in detail, which has an important directive significance to extend the application field of multilevel non-diffracting beams.

2018 Vol. 47 (7): 708003-0708003 [Abstract] ( 29 ) PDF (5193 KB)   ( 36 )
Generation of Partially Coherent Caustic Beam and Its Spatial Correlation Properties
YANG Yan-fei, WU Feng-tie, HU Han-qing, HU Run, ZHU Qing-zhi

A new method is introduced by using the cross-spectral density function to describe the caustics beam, which is extended from fully coherent cases to the field of partially coherent cases for the first time. And the propagation formula of caustics beam is derived in the free space combined with the Fresnel Kirchhoff diffraction integral theroy. The influence of astigmatism introduced by tilted axicon at various inclination angles on partially coherent caustic beam with respect to the propagation axis was studied theoretically and experimentally. Furthermore, the partially coherent caustics beam is invested that is effected by the field coherence on the partially coherent caustic beam. Results show that the intensity contrast ratio between light focus and the surrounding dark regions can be reduced with the decrease of the spatial coherent lengths.

2018 Vol. 47 (7): 708004-0708004 [Abstract] ( 32 ) PDF (3192 KB)   ( 77 )
Optical Devices
Micro Current High Efficiency 650 nm Resonant Cavity Light Emitting Diode
WANG Yuan-cheng, LI Jian-jun, WANG Hai-kuo, WANG Meng-huan, YUAN Ze-xu, ZOU De-shu

Based on the micro cavity theory and the film optical transmission matrix model, the resonant cavity light emitting diodes with different aperturehave been designed and fabricated. Through the design of epitaxial structure as well as the preparation and testing of devices, in this paper, the effects of microcavity structure, cavity spectrum detuning and effective radiation area on the luminous efficiency, peak wavelength and full width of the half wave were investigated in detail. In the end, the bright current of the device is reduced and the external quantum efficiency of the device is improved. The device can produce visible light intensity at the 100 μA bias current. At 1mA current, the power is 0.16 mW and the external quantum efficiency is 7%. The peak wavelength of the device is 650 nm, which had not changed with the current in the range of 0.1~7 mA. The far-field distribution is circular spot with uniform symmetry, and the horizontal and vertical divergence angles are 46° and 48° respectively. Compared with ordinary light emitting diode, the device has higher luminous efficiency and better monochromaticity, directivity, wavelength stability. This research has provided devices for realizing high current luminescent driven by micro current, and provided references for the research of the photoelectric characteristics of resonant cavity light emitting diodes under micro current.

2018 Vol. 47 (7): 723001-0723001 [Abstract] ( 38 ) PDF (2515 KB)   ( 29 )
Tunable Pass-band Filter Based on One Dimensional Split Ring Resonant Structure
ZHANG Hao, TONG Yuan-wei

Based on equivalent LC resonant circuit, the response between the resonance frequency and the electric parameters of the equivalent circuit were analyzed. Different from the traditional transmission line loaded with split-ring resonator structure, two different split-ring resonator structures were designed as the transmission medium. In consequence, two passband filters are achieved in this paper which bandwidth are 300 MHz and 200 MHz with square and circular split-ring resonator respectively, by loading with varactor and bias circuit in the split-ring resonator structure, two continuous tunable passband filters are finished in the end. The difference in surface current density between the square and circular split-ring resonator is given in this paper, the transmission coefficient of the square split-ring resonator is 3dB higher than the circulal's within the passband, analysis shows the effective distance is one of important reason for the coupling efficiency.

2018 Vol. 47 (7): 723002-0723002 [Abstract] ( 26 ) PDF (2142 KB)   ( 36 )
Broadband Tunable Filter Based on Square Loop Metamaterial
ZHAO Ya-juan, ZHOU Bi-cheng, ZHANG Han, ZHANG Ting, LI Bao-yi, WANG Dong-hong

The loading technology of microcontroller circuit was used to change the spatial distribution of relative permittivity and relative permeability in different time, the metamaterials spatial filter can be tuned in frequency. A square loop metamaterial filter was designed with unit structure size of 18.5 mm×18.5 mm, which can be continuously tunable in the X band by loading varactor diode on the unit structure. When the varactor diode increases from 0.15 pF to 0.70 pF, the simulation results show that the center frequency of the filter is decreased from 11.8 GHz to 10.5 GHz, the bandwidth is 16.3% (10.2~12.0 GHz), and the return loss minimum is 22 dB, the insertion loss maximum is 0.6 dB. The measured results show that the center frequency of the filter is decreased from 11.7 GHz to 10.3 GHz, the bandwidth is 17.2% (10.1~12.0 GHz), and the return loss minimum is 25 dB, the insertion loss maximum is 0.5 dB.

2018 Vol. 47 (7): 723003-0723003 [Abstract] ( 52 ) PDF (2441 KB)   ( 62 )
Scattering
Truncated Singular Value Decomposition Inversion Based on Extended Nuclear Matrix in Dynamic Light Scattering
HUANG Yu, SHEN Jin, XU Min, SUN Cheng, LIU Wei, SUN Xian-ming, WANG Ya-jing

In order to solve the problem of particle size information loss in dynamic light scattering inversion by truncated singular value decomposition method, on the base of analyzing the difference of particle size information distribution in autocorrelation function at different delay time, extended truncated singular value decomposition method was proposed which uses nuclear matrix and particle size information distribution in autocorrelation function at different delay time in the same angle to build the extended nuclear matrix. The method adjusts the contribution of the original nucleus matrix datas to the SNR at the same time using the particle size information at each delay time in the autocorrelation function, thereby preserves more effective singular values and reduces information loss due to singular value truncation. On the basis of ensuring noise reduction, the information utilization for the autocorrelation function is improved. At noise level 1×10-3, the datas a set of single peak width distribution (260 nm) and three sets of bimodal particle distributions (250/750 nm), (270/800 nm) and (306/974 nm) simulated in dynamic light scattering in single angle, 3 angles and 6 angles was inverted. The results show that, compared with truncated singular value decomposition method, the peak size errors and distribution errors obtained by extended truncated singular value decomposition method are obviously reduced. The inversion of the measured datas for 306/974 nm particle system in 6-angles shows that the peak particle size error obtained by the extended truncated singular value decomposition method is reduced from 0.032/0.016 by the truncated singular value decomposition method to 0.029/0.006, and peak ratio is closer to actual value.

2018 Vol. 47 (7): 729001-0729001 [Abstract] ( 64 ) PDF (3610 KB)   ( 64 )
Materials
Optical Properties Simulating Calculation of the F or F+ Center in LuPO4 Crystal
LI Jin, LIU Ting-yu, FU Ming-xue, LU Xiao-xiao

The defect formation energy of LuPO4 crystal is calculated by generalized gradient approximation combined with plane wave pseudo-potential based on density functional theory. The periodic arrangement of the defect introduces artifical interactions is corrected. The oxygen vacancy defect formation energy in different charged states is obtained accurately, and band gap is modified through Hybrid functional. The optical line shapes are described by the defect formation energy and electron-phonon coupling. The comparison of LuPO4:Nd experimental and calculated results shows the absorption peak of F center are superimposed on Nd3+ 5d-4f emission (located at 189 nm). It is inferred that F center is found to be responsible for the limited light yield in LuPO4:Nd.

2018 Vol. 47 (7): 716001-0716001 [Abstract] ( 32 ) PDF (835 KB)   ( 55 )
Hydrothermal Synthesis and the Study of Fluorescence Properties of AgInS2 Quantum Dots
HU Xiao-bo, CHEN Ting, XU Yan-qiao, ZHANG Xiao-jun, JIANG Wei-hui, JIANG Wan

Water-soluble AgInS2 quantum dots were synthesized via hydrothermal method using L-glutathione and sodium citrate as ligands. The effects of cation concentration, addition amount of ligands and pH values on the phase, morphology and fluorescence properties of AgInS2 quantum dots were systematically studied by X-ray diffraction, transmission electron microscopy, UV-Vis absorption spectra and photoluminescence spectra, respectively. The results showed that the particle size of AgInS2 quantum dots increased with the increase of cation concentration, which caused a systematic red shift from 614.7 nm to 675.6 nm in the photoluminescence spectra. Meanwhile, the Ag+ content in quantum dots decreased slightly due to the substitution of Ag+ by In3+, and the resulted defect of InAg could be served as the radiation recombination channel of excitons in AgInS2 quantum dots, which was propitious to improve its fluorescence emission efficiency. The fluorescence intensity of AgInS2 quantum dots reached to the maximum with the cation concentration of 0.7 mmol/L. Moreover, the ligands can effectively passivate the surface states and improve fluorescence properties of quantum dots. The AgInS2 quantum dots showed the strongest emission with the glutathione/Ag+ ratio at 20, and the sodium citrate/In3+ ratio at 7. The maximum quantum yields of AgInS2 quantum dots reached 10.1% due to the pronounced passivating effect on surface defects by ligands when the pH value of the solution was adjusted to 9, however the high pH values interfered with the combination between ligands and quantum dots, which induced a large number of surface non-radiative recombination defects, leading to the decrease of quantum yields. The infrared spectrometry results showed that glutathione and sodium citrate were mainly coordinated with AgInS2 quantum dots by the -SH, -NHR and -COO- groups. In addition, the surface of quantum dots was negatively charged, which demonstrates that the AgInS2 quantum dots possess good dispersibility and excellent chemical stability, showing wide application prospects in the biological imaging fields.

2018 Vol. 47 (7): 716002-0716002 [Abstract] ( 20 ) PDF (5800 KB)   ( 24 )
Atmospheric and oceanic optics
Experimental Study on Wind Field Simulation of Asymmetric Spatial Heterodyne Spectrometer
JIANG Tong, SHI Hai-liang, SHEN Jing, DAI Hai-shan, XIONG Wei

In order to verify the accuracy level of the wind field in the middle and upper atmosphere, the simulation of the ground wind field is carried out by the asymmetrical spatial heterodyne spectrometer. The basic principle of wind field detection by asymmetric spatial heterodyne spectroscopy and the basic performance parameters of the developed spectrometer are introduced. The wind field simulation detection experiment is designed by the wind speed simulation device, and the inaccuracy of the motor speed, the installation mechanical angle, the measuring value of the radius of the turntable and the angle of the ray incident during the simulation of wind speed are also introduced. The theoretical wind speed error of the device is no more than 1.3%, which is able to meet the requirements of wind field simulation detection and verification. By using the wind speed simulation device and adjusting the speed experiment of different motor, the data of 24 sets of measured results of simulated wind speed in 34.19~78.63 m/s are obtained. The simulation covers the range of wind speed in middle and upper atmosphere, error correction and wind velocity inversion for the measured data, and the results of wind velocity measured by the asymmetric spatial heterodyne spectrometer and the results of wind velocity measurement. The accuracy of wind velocity detection by 3.28 m/s of standard deviation of wind speed error is obtained after theoretical simulation of wind velocity comparison. It is proved that asymmetric spatial heterodyne spectroscopy has the characteristics of high phase sensitivity and high precision.

2018 Vol. 47 (7): 701001-0701001 [Abstract] ( 66 ) PDF (2129 KB)   ( 82 )
Aerosol Extinction Retrieved with Optical Estimation Algorithm Based on Multi-axis Differential Optical Absorption Spectroscopy
MOU Fu-sheng, LUO Jing, LI Su-wen, WANG Jia-wei, SHI Rui-rui, WEI Min-hong

A method for retrieving aerosol extinction coefficient vertical profile based on multi-axis differential absorption spectroscopy was studied, which is based on nonlinear optimal estimation algorithm. The aerosol extinction profile and optical thickness are retrieved from the concentration of O4 gas differential diagonal column, combined with the atmospheric radiation transmission model, by the multi axis differential absorption spectrometer. Field observation experiments were carried out in Huaibei area in July and August, 2017. The difference between the simulated results of O4 differential column with low elevation angle (less than 15 degrees) is higher than 0.9, and the aerosol state of troposphere is well retrieved. The study shows that the overall aerosol content in Huaibei is low in summer, and the daily average optical thickness of the two day high value weather (July 24th and August 12th) is 0.65 and 0.59, respectively, 1.6 times and 1.4 times the seasonal average. Through the aerosol extinction profile time series, we can see that the high values of aerosol over two days are below 0.5 km, and the pollution is mainly caused by local accumulation.

2018 Vol. 47 (7): 701002-0701002 [Abstract] ( 24 ) PDF (2966 KB)   ( 31 )
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