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NUCLEAR TECHNIQUES
2019 Vol.48 Issue.10
Published 2019-10-25

Holography
Spectroscopy
Diffraction and Gratings
Materials
Detectors
Atmospheric and Oceanic Optics
Contents
Fiber Optics and Optical Communications
Image Processing
Thin Films
Special Issue on Optical Soliton
      
Contents
2019 Vol. 48 (10): 0-0 [Abstract] ( 21 ) PDF (298 KB)   ( 22 )
Special Issue on Optical Soliton
Propagation of Nonlocal Vector Solitons under Gauss Barrier or Trap
WENG Yuan-hang, WANG Hong, CHEN Pei-jun

The propagation of vector solitons in nonlocal nonlinear media with a Gauss barrier or a Gauss trap is described by the coupled nonlocal nonlinear Schrodinger equations with Gauss-type linear potential. These equations are numerically calculated by the square operator method, and the propagation of vector solitons is simulated by the step-step method. In nonlocal nonlinear bulk media, the components of out-of-phase vector solitons are always separated spontaneously, and the repulsion between them can be suppressed by a Gauss barrier. The components of in-phase vector solitons are always fused spontaneously, and the attraction between them can be suppressed by a Gauss trap. By quantitatively analyzing the relationship between the barrier heigh/depth or width and the distance between two components of vector solitons at the normalized transmission distance of 500, it is found that if the heigh/depth and width of barrier/trap are too large or too small, Gauss linear potential can not suppress this process, or even worsen it. For out-of-phase solitons, the Gauss barrier that can effectively suppress the separation should be set to 1.10 in height and 1.00 in width. For in-phase solitons, the Gauss potential well that can effectively suppress the fusion should be set to -1.50 in depth and 1.00 in width. Results in this paper may benefit the future researches about all-optical switch, optical logic-gate, optical computing and other optical control technologies.

2019 Vol. 48 (10): 1048001-1048001 [Abstract] ( 63 ) PDF (3711 KB)   ( 73 )
Bright Solitons in Liquid Crystals with Competing Nonlocal Nonlinearities
PU Shao-zhi, LI Ying-jia, CONG Wen-bo, ZHANG Liu-yang

A model which is proposed by JUNG P S et al. is employed to demonstrate analytically properties of individual bright solitons in liquid crystals with competing nonlinearities under the condition of unequal nonlocality of the thermal effect and the reorientational effect. The evolution of the parameters, such as amplitude, width, chirp and phase with transmission distance, are obtained by the variational method. The amplitude and width are closely related to the beam power. The beam width decreases monotonously with the increase of thermal nonlocality and increases monotonously with the increase of thermal nonlinearity. In this case, the equivalent potential which is relate the power of the beams is also obtained. It is predicted by the potential that the larger the incident beam power is, the smaller the bright soliton width is. It is obtained by the variational method that the beam width oscillates periodically with the transmission distance when the incident power is 4 or 8. There are obvious differences between the two oscillation trends. When the power is 4, the width of the beam is always greater than or equal to the initial width. When the power is 8, the width of the beam is always less than or equal to the initial width. The variation of beam width with transmission distance is consistent with the numerical simulation results.

2019 Vol. 48 (10): 1048002-1048002 [Abstract] ( 26 ) PDF (1836 KB)   ( 23 )
Generation of High Repetition Rate Broadband Flat Coherent Optical Frequency Comb Based on Tantalum Pentoxide Integrated Nonlinear Optical Waveguide
WU Chun-jiang, FENG Su-chun

Through the waveguide structure design and dispersion engineering, based on the soliton pulse compression, self-phase modulation, and optical wave breaking, a 0.22 m anomalous dispersion tantalum pentoxide waveguide cascaded with a 0.9 m normal dispersion tantalum pentoxide waveguide was used to produce a flat optical frequency comb with a 4 dB flatness and 60 nm bandwidth in the 1 520 nm to 1 580 nm. The spectrogram evolution during the pulse transmission process was analyzed through the X-Frog technique, and the coherence of the optical frequency comb were also studied. The analysis indicates that the self-phase modulation and optical wave breaking effects make the comb spectrum envelop broadened and flattened. The first-order mutual coherence function calculation indicates that the optical frequency comb has good spectral coherence. The simulation results show that the tantalum pentoxide integrated nonlinear optical waveguide has a good prospect in the generation of high repetition rate flat coherent broadband optical frequency comb.

2019 Vol. 48 (10): 1048003-1048003 [Abstract] ( 45 ) PDF (6293 KB)   ( 57 )
Propagation Properties of Airy-Gaussian Beams in a Biased Photovoltaic-photorefractive Crystal
ZHANG Tuo, CHEN Wei-jun, MU Yi-ning, LIU Chun-yang, PENG Jun-qi

Propagation properties of Airy-Gaussian beams in a biased photovoltaic-photorefractive crystal are numerically investigated by using split-step Fourier method. The results show that breathing solitons that propagate stablely along a straight line can be generated when the initial amplitude of the input Airy-Gaussian beams and the external bias field of the crystal are in certain ranges. The peak intensity and the breathing period of the soliton can be controlled by adjusting the initial amplitude and the external bias field. With the increase of the initial light field distribution factor, the mean peak intensity of the soliton firstly increases and then decreases, whereas the breathing period firstly decreases and then increases. With the increase of the beam decay coefficient, the mean peak intensity of the soliton firstly increases, then decreases, and increases again. In addition, the propagation direction of the soliton can tilt to the left with a negative launch angle and to the right with a positive launch angle. The launch angle only affects the output position of the soliton and has no influence on the intensity, width and breathing period of the soliton.

2019 Vol. 48 (10): 1048004-1048004 [Abstract] ( 36 ) PDF (3916 KB)   ( 63 )
Manipulation of Gaussian Beam Based on Fractional Schrödinger Equation
WANG Dong-dong, ZANG Feng, LI Lu

The influences of Lévy index, chirp parameter and potential depth on the propagation dynamics of chirped Gaussian beam are investigated numerically based on the fractional Schrödinger equation with a harmonic potential. It is found that, for fixed chirp parameter and potential depth, the propagation period decreases and the deviation distance increases with increasing of Lévy index. For fixed Lévy index and potential depth, the propagation period and the deviation distance increase as the chirp parameter increases. The period and the deviation distance are inversely proportional to the potential coefficient regardless of the values of Lévy index and chirp parameter. The results indicate that the beam propagation can be effectively controlled by adjusting Lévy index, chirp parameter and potential depth, which can inspire new ideas in the manufacture of optical switches.

2019 Vol. 48 (10): 1048005-1048005 [Abstract] ( 30 ) PDF (2735 KB)   ( 73 )
Properties of Multipolar Bright Solitons in Non-local Nonlinear Coupling Medium
FANG Ping-ping, JIN Xin-wei, LIN Ji

The existence conditions and stable propagation of multipole bright solitons in the one dimensional nonlocal nonlinear couple are reported. By means of Newton iterative method, the dipolar and tripolar bright solitons are obtained. Because the attraction of solitons is larger than their repellant due to the strong nonlocal response, the propagation of the dipolar soliton is unstable, and two solitons attract each other and then merge into one soliton. With the decrease of the nonlocal parameters, the propagations of the dipolar solitons are stable when the balance of the nonlinear effect and diffraction effect is achieving. On the other hand, with the decrease of the propagation constant, the amplitude of solitons increases and the beamwidth is changed to be narrow, the propagation of solitons is stable. For tripolar bright solitons, the coupled tripole solitons can not propagate steadily when the nonlocal parameters are small. After a distance of propagation, the tripole solitons collide and merge into dipolar solitons, finally the dipolar solitons merge into an oscillatory beam. With the nonlocal parameters increasing, the propagation of the tripolar bright solitons come to be more stable. Taking the propagation constant negative and decreasing its absolute value, the amplitudes of solitons increase, the beamwidths decrease, and the propagation stability of the tripole solitons is increasing. Finally, the propagation stability of these bright solitons is further verified by adding white noise.

2019 Vol. 48 (10): 1048006-1048006 [Abstract] ( 26 ) PDF (5403 KB)   ( 28 )
Thin Films
Preparation and Electrochromic Properties of WO3/Ag Composite Film
MIAO Zhuang, YANG Xue, YANG Ji-kai, HOU Zhi-peng, ZHANG Yu-fei, WANG Xin, WANG Guo-zheng

WO3 nanoblocks were prepared by hydrothermal method on FTO glass, and WO3/Ag composite film was prepared by electrodepositing different content (20 s, 50 s, 80 s) of Ag nanoparticles onto WO3 nanoblocks. Characterization of WO3/Ag composite films was confirmed by X-ray diffraction analysis, scanning electron microscopy and energy spectroscopy. The parameters of electrochromic reversibility, response time, coloration efficiency and spectral transmittance were obtained by electrochomical measurement technologies and spectral tests. Then, the electrochromic properties were analyzed. The WO3/Ag composite films show the higher electrochromic properties compared with the WO3 nanoblock film. The effects of different Ag nanoparticle content on the electrochromic properties of WO3/Ag composite films were also studied. The results show that the WO3/Ag composite film deposited for 50 s has the best electrochromic properties.

2019 Vol. 48 (10): 1031001-1031001 [Abstract] ( 29 ) PDF (4270 KB)   ( 24 )
Epitaxial InAs Films on GaSb Substrate and Study on Optical Properties
ZHANG Jian, TANG Ji-long, KANG Yu-bin, FANG Xuan, FANG Dan, WANG Deng-kui, LIN Feng-yuan, WEI Zhi-peng

The ternary alloy InAsSb of the low Sb component as the buffer layer, which reduces the mismatch of the film, was grown on the GaSb (100) substrate by using the molecular beam epitaxy, and then regrown the InAs film. Real-time in situ monitoring by reflection high energy electron diffraction throughout the growth process. Following the growth of the InAs film, the electron diffraction pattern showed a clear reconstitution line, with the surface of the film having atomic flatness. Atomic Force Microscopy is used to characterize InAs films, and the results show that the roughness of epitaxial InAs film on the InAsSb buffer with lower Sb components is reduced by about 2.5 times than the roughness of epitaxial InAs film on the InAsSb buffer with higher Sb components. X-ray diffraction and simulation were performed for epitaxial InAs films on ternary alloy InAsSb buffer with different Sb composition. The results show that the full width half maximun of the diffraction peak of the epitaxial InAs film on the lower Sb composition of InAsSb buffer layer is smaller. It is indicated that the InAsSb with a low Sb component acting as a buffer layer can reduce the internal stress of the InAs film and can improve the crystal quality of the InAs film. The luminescence properties of InAs films with high crystal quality were studied by photoluminescence spectroscopy. The luminescence peak of InAs is about 0.418 eV at 10 K, which is free exciton luminescence.

2019 Vol. 48 (10): 1031002-1031002 [Abstract] ( 54 ) PDF (3387 KB)   ( 38 )
Materials
Hydrothermal Synthesis and the Study of Fluorescence Properties of Quaternary Ag-In-Zn-S Quantum Dots
CHEN Ting, HU Xiao-bo, XU Yan-qiao, JIANG Wei-hui, JIANG Wan, XIE Zhi-xiang

Ag-In-Zn-S quantum dots (AIZS QDs) were prepared by hydrothermal method using inorganic metal salts as raw materials, Glutathione (GSH) and Sodium Citrate (SC) as ligands. The effects of pH values, Ag/In and Ag/Zn ratios on phase, morphology, and fluorescence properties were systematically investigated, and the phase, morphology and fluorescence properties of AIZS QDs were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Ultraviolet and visible absorption spectra, photoluminescence spectra, respectively. The results showed that the AIZS QDs with excellent fluorescence properties could be prepared via green and facile hydrothermal method. The surface defects of AIZS QDs could be effectively passivated by ligands with the increase of pH values (pH=7~9), resulting in the enhanced emission intensity. Moreover, the emission wavelength of AIZS QDs located the range of 632.1 nm~588.9 nm with the Ag/In ratios of 1:1~1:11, and their Quantum Yields (QYs) could reach up to 27.3% with the Ag/In ratio of 1:7. Furthermore, the emission peak showed a systematic blue-shift from 592.5 nm to 570.3 nm by varying the Ag/Zn ratio from 1:0.5 to 1:3.0 due to the increased alloying effect. AIZS QDs exhibited the strongest emission and the maximum QYs of could be further increased to 35.3% with the Ag/Zn ratio of 1:1.5, indicating that the incorporation of Zn2+ could effectively improve the fluorescence properties of AIZS QDs by stabilizing the lattice and suppressing the non-radiative recombination. Under the forward bias current of 200 mA, the AIZS QDs-based white light-emitting diode (WLED) exhibited a high Color Rendering Index (CRI) of 80.1, Luminous Efficiency (LE) of 60.8 lm/W with the Commission Internationale de I'Eclairage (CIE) color coordinate of (0.29, 0.35), demonstrating the prospective application of obtained QDs in solid-state lighting devices.

2019 Vol. 48 (10): 1016001-1016001 [Abstract] ( 30 ) PDF (6242 KB)   ( 36 )
Effect of Purified Solvents on the Performance of Quantum Dots Synthesized at Room Temperature
LI Yue, XIE Qi-fei, WANG Xin-zhong, MA Yan-hong

CsPbBr3 quantum dots were prepared by room temperature recrystallization. The quantum dot crude solution was purified by high-speed centrifugation using six common polar solvents. The photoluminescence spectrum after each step in the purification process was monitored and the absorption spectrum was used. Fluorescence lifetime, X-ray diffraction analysis and transmission electron microscopy were used to characterize the CsPbBr3 quantum dots purified by six polar solvents. The results show that cubic phase CsPbBr3 quantum dots with good crystallinity can be obtained by purification of six polar solvents. The supernatant obtained by the second centrifugation during purification process using six different polar solvents has the most uniform half-width and peak wavelength; except for ethyl acetate, the supernatant obtained by the second centrifugation has the highest quantum yield; in contrast, the CsPbBr3 quantum dots obtained by isobutanol purification have higher Luminescence performance.

2019 Vol. 48 (10): 1016002-1016002 [Abstract] ( 20 ) PDF (3500 KB)   ( 35 )
Holography
Super-resolution Experimental Study of Digital Holographic Microscopy Based on POCS
FENG Dan-qing, TIAN Ai-ling, LIU Bing-cai, FENG Fang, WANG Da-sen, LIU Wei-guo

In order to improve the reconstruction effect of digital holographic microscopy system, the Project Onto Convex Set (POCS) algorithm is applied to digital holography to achieve super-resolution reconstruction of hologram. Firstly, based on the theory of digital holography and POCS algorithm, the optical path of transmissive off-axis digital holography is established. Then, the resolution board is used to verify the effectiveness of the POCS algorithm in hologram super-resolution restoration. Finally, the feasibility of the method in 3D reconstruction is verified by microlens array. The residual estimation results of the low-resolution hologram and the super-resolution restored hologram are respectively estimated by the three-dimensional reconstruction result of the reference hologram. The PV and RMS of the latter residuals are reduced by 36.88% and 70.66%, respectively, which proves that the method can achieve super-resolution reconstruction of digital holography.

2019 Vol. 48 (10): 1009001-1009001 [Abstract] ( 37 ) PDF (3565 KB)   ( 42 )
Phase Measurement Based on Nonlinearity Correction and Filter of System
QIAO Nao-sheng, LONG Yong-fu, YAN Bo, CAO Bin-fang, LI Xiao-qin

The nonlinearity between projector output and CCD input deformed fringe intensity in phase measurement system results in spectrum aliasing and affects measurement accuracy. In order to eliminate the nonlinearity relationgship between them and improve phase measurement accuracy, the basic causes of system nonlinearity are analyzed, and a new phase measurement method based on system nonlinearity correction and filtering is proposed. Firstly, the system nonlinearity caused by the gamma distortion in the projector is corrected. Then, the output spectrum is filtered by low-pass filter, only the fundamental frequency component of the spectrum is retained. Finally, the phase measurement of deformed fringes is carried out by four-step phase-shift method. The results of MATLAB simulation and practical experiment show that the proposed method has better effect of system nonlinearity correction and filtering, and is helpful to improve the phase measurement accuracy.

2019 Vol. 48 (10): 1009002-1009002 [Abstract] ( 23 ) PDF (4221 KB)   ( 66 )
Atmospheric and Oceanic Optics
Parameter Design and Performance Analysis of Bistatic Helium Lidar System
PAN Ting-yu, SUN Dong-song, ZHAO Ruo-can, LAN Jia-xin, HAN Yu-li, CHEN Ting-di, XUE Xiang-hui, TANG Lei

According to the atmospheric continuous laser beam imaging technology, the corresponding resolution range for the distance between separated transmitter and receiver on bistatic helium lidar system is obtained, as well as the relationship between the single-row CCD pixels and the altitude, and the variation curve of resolution range with different altitudes. Moreover, the corresponding relation between the number of photons received by the system's single-row pixels and the altitude under different metastable helium densities is analyzed, and the signal to noise ratio and relative error varied with altitude are obtained. The simulation results indicate that the signal to noise ratio can be improved by increasing the integration time. In the range of altitude from 400 km to 1 000 km, when the integration time is 2 h and the range resolution is 50 km, the signal to noise ratio is in the range from 10 to 65 and the relative error is less than 10%. These results prove that adopting the bistatic helium resonance fluorescence lidar system can detect the metastable helium density of the 200~1 000 km thermosphere, which provides a reference for further perfecting and optimizing the scheme of the bistatic helium resonance fluorescence lidar system.

2019 Vol. 48 (10): 1001001-1001001 [Abstract] ( 41 ) PDF (3179 KB)   ( 25 )
Numerical Simulation of Propagation Performance of Super-continuum Laser in Turbulent Atmosphere
LI Ya-qian, ZHU Wen-yue, QIAN Xian-mei

Considering the atmospheric extinction and turbulent effects, beam spreading, beam wandering and intensity scintillation of super-continuum laser propagating in atmospheric turbulence are studied by using multi-phase screen simulation method. And the difference of propagation properties between super-continuum laser and monochrome laser is analyzed. The simulation results show that, to super-continuum source, with the increase of turbulence strength or the increase of source coherence, relative beam spreading becomes more serious. As turbulence strength increases, beam wandering becomes more pronounced. And the RMS of beam wandering is insensitive to the variation of source coherent degree. Scintillation index and the dependence of scintillation index on off-axis distance may decline by reducing source coherence. Compared with the monochromatic laser, the relative beam spreading and intensity scintillation of super-continuum laser are less affected by turbulence, while the difference of beam wandering is not obvious. The agreement between results of numerical simulations and the theoretical analysis results of monochromatic laser propagating in atmospheric turbulence illustrated the reliability of the numerical simulation process. This study not only proposes an effective simulation method to obtain the atmospheric propagation characteristics of super-continuum laser, but also provides meaningful reference for the application of super-continuum laser.

2019 Vol. 48 (10): 1001002-1001002 [Abstract] ( 29 ) PDF (3006 KB)   ( 15 )
Influence of Pressure of Jet on Hypersonic Flow Field Modulation Transfer Function
ZHAO Xin-hai, YI Shi-he, DING Hao-lin, OU-YANG Tian-ci, SHI Yang

An aero-optical ground test platform based on the hypersonic (Ma=6.0) gun tunnel was built. The test object was an optical dome model with cooling jet structure. Combined with background oriented schlieren technology, a high-speed camera was used to obtain the light deflection information of the flow field with five different pressure of jet value:0, 04, 1.0, 1.16 and 1.8. And the corresponding modulation transfer function was calculated with the geometric optics theory. The experimental results show that the increase of pressure ratio of jet value can reduce the envelope area of the modulation transfer function of the flow direction and span direction. The flow direction modulation transfer function fluctuates between 2~4 lp/mm under larger pressure ratio of jet value.

2019 Vol. 48 (10): 1001003-1001003 [Abstract] ( 18 ) PDF (3912 KB)   ( 11 )
Detectors
Achieving High-detection Organic Photodetectors Covering the Visible Range by Using a Ternary Active Layer
AN Tao, WANG Yong-qiang, ZHANG Jun

A high detectivity organic photodetector with active layer P3HT:PBDT-TT-C:PC61BM covering the visible wavelength range was prepared by solution spin coating and high vacuum evaporation. The effects of PBDT-TT-C doping P3HT:PC61BM on the optical properties of the active layer films were investigated by atomic force microscopy, UV-visible absorption spectroscopy and fluorescence spectroscopy. It was found that when the mass ratio of P3HT:PBDT-TT-C:PC61BM in the active layer was 8:2:10, the response spectrum of the active layer was broadened to 350~780 nm. The optical responsiveness and external quantum efficiency of the red, green and blue primary colors of the detector under the bias of -1 V reached 422 mA/W, 464 mA/W, 286 mA/W and 83%, 108%, 77%, respectively, and the specific detectivity reached above 1012 Jones. The results show that the organic material with an organic material complementary is doped. On the basis of ensuring the microscopic morphology of the film, By adjusting the mass ratio of the ternary mixed material, not only the carrier generation and transport can be optimized, the photocurrent of the device is improved, but also the crystallization of the thin film can be promoted by the incorporation of the third component, and the dark current of the device can be reduced.

2019 Vol. 48 (10): 1004001-1004001 [Abstract] ( 24 ) PDF (5555 KB)   ( 21 )
Photoelectronics Multiplication Organic Photodetecors with Controllable Operating Voltage
AN Tao, LIU Xin-ying

The adjustable working voltage of device is realized by changing the ratio of donor-acceptor in the active layer of the organic detector. The influence mechanism of different PC61BM concentration on the hole tunneling injection voltage in PBDT-TT-F:PC61BM:C60 photoelectronics multiplication device was studied. Under the adjacent 600% external quantum efficiency value, by adjusting the concentration of PC61BM, we can obtain a low device operating voltage of -3 V and a high device operating voltage of -6 V. The results show that the hole transport ability and exciton dissociation efficiency of the active layers are changed by adjusting PC61BM concentration, which causes the change of the collection efficiency of hole injection current for anode. Finally, the regulation of device operating voltage is achieved. This paper provides an universal method for obtaining photoelectronics multiplication organic photodetectors with facile fabrication, low and controllable operating voltage.

2019 Vol. 48 (10): 1004002-1004002 [Abstract] ( 30 ) PDF (2727 KB)   ( 27 )
Angular Momentum Detector Based on Surface Plasmons
QIU Peng, HU Zheng-da, KONG Yan, JIANG Zhi-long, LIU Cheng, WANG Shou-yu

In order to accurately detect the angular momentum of light, an angular momentum detector based on surface plasmons was designed. The detector is small and simple, which can detect the incident light only by etching the designed nanoslit array on a gold film. When incident light illuminates the detector, the polarization of incident light can be distinguished according to the coupling direction of surface plasmons. Moreover, by measuring the light intensity of the outgoing port compared with the total intensity of the coupling direction port, the accurate topological charge of orbital angular momentum between -1 and +1 can be quantitatively calculated. The nano-structure detector can accurately identify the angular momentum of incident light, providing a new idea for the design and development of on-chip optical system.

2019 Vol. 48 (10): 1004003-1004003 [Abstract] ( 46 ) PDF (4053 KB)   ( 81 )
Application of Wavelet Threshold Denoising Algorithm in Photodetector Signal Processing
WU Yan, ZHANG Rong-zhu

To overcome the shortcomings of the traditional noise reduction processing in photodetectors, a novel wavelet threshold denoising algorithm is presented. A threshold function with parameters and layer-by-layer threshold are combined in the algorithm. By adjusting the parameters, a threshold function can be generated, which value is between soft and hard threshold functions, and can realize the smooth transition at the critical threshold. During the application, the threshold can be changed with the change of decomposition layers. The individual decomposition layer has adaptive characteristics. So it can reduce the fixed deviation in the wavelet threshold processing, and then the unnecessary noise can be restrained while the original signal is remained. The results of simulation and experiment show that the SNR of signal processed by the wavelet threshold denoising algorithm are relatively high and the mean square error is small. Furthermore, the algorithm can effectively suppress the interference of noise on the output signal of photodetector.

2019 Vol. 48 (10): 1004004-1004004 [Abstract] ( 20 ) PDF (3889 KB)   ( 29 )
Spectroscopy
Data Denoising Method for Rock Identification Based on LIBS Technology
WANG Chong, ZHANG Xiao-mo, ZHU Xiang-ping, LUO Wen-feng, SHAN Juan

There have been confront with a low identification accuracy problem due to the poor repeatability and high data residual value of laser-induced breakdown spectrum. In order to solve such problems, an distinguishing method of abnormal value based on Grubbs criterion (3δ-Grubbs) was proposed. The method can effectively replace the data of large residual values to reduce the probability of over-fitting in the classification recognition algorithm. Finally, by using three classification recognition algorithms:linear discriminant analysis, random forest classification and support vector machine, we identified the LIBS spectrum of rocks. Before the data noise reduces, the recognition accuracy of the three methods were:linear discriminant analysis 79.6%, random forest classification 75.2%, support vector machine 94.5%.After data noise is reduced,the recognition accuracy of the three methods is as follows:linear discriminant analysis 92%, random forest classification 97%, support vector machine 99.4%.

2019 Vol. 48 (10): 1030001-1030001 [Abstract] ( 27 ) PDF (3949 KB)   ( 36 )
Mineral Element Abundance Identification Based on LIBS Emission Line Selection by Loading Space Distance of Principal Component Analysis
GUO Kai-chen, WU Zhong-chen, ZHU Xiang-ping, LING Zong-cheng, ZHANG Jiang, LI Yun, QIAN Mao-cheng

The concentration and laser-induced breakdown spectroscopy data of 64 pre-flight calibration samples, published by the ChemCam team, were used as objects of research. Principal component analysis loading space distance method was used to analyze the target element, the most sensitive laser-induced breakdown spectral line of the target element was selected, and the mineral element species and abundance were identified with the identification accuracy up to 92.8% based on this method. The result shows that principal component analysis loading space distance can be used as a criterion to obtain the critical element information of minerals element abundance before, if aim to serve for, quantitative analysis. This study reduces the difficulty in rock/mineral classification and is beneficial to unknown minerals analysis, which offers an effective identification strategy for the Martian surface rock type analysis.

2019 Vol. 48 (10): 1030002-1030002 [Abstract] ( 28 ) PDF (3322 KB)   ( 25 )
Research on Laser Damage Induced by Laser Plasma Based on Finite Element Method
YU Hui-bo, JIANG Yue, SHEN Xiong, FENG Guo-ying, ZHENG Zhou, JIA Yao-feng, HAN Jing-hua

The surface and cross-section damage morphology of fused silica glass elements under the action of nanosecond laser plasma shock waves was investigated. We use the finite element method to simulate the propagation law of shock wave inside fused silica glass, and analyze the damage formation mechanism based on the stress distribution law of shock wave inside glass. It is found that under the action of shock wave, the fused silica glass will be subjected to compressive stress along the wave front direction and tensile stress along the wave front direction. These two stresses cause arc-like layered fracture and radial fracture at the center of the laser irradiation. The superposition of the reflection of the shock wave causes the local tensile stress to increase, which caused damage to the rear surface. Through the finite element method, we intuitively analyzed the effect of plasma shock wave on optical components, and analyzed the damage mechanism of optical components under plasma shock waves.

2019 Vol. 48 (10): 1030003-1030003 [Abstract] ( 18 ) PDF (2442 KB)   ( 29 )
Real-time Detection of SF6 Leakage in Large Area Based on Quantum Cascade Laser
TANG Feng, LIU Shun-gui, Lü Qi-shen, LI Xin-tian, HE Shu-kai, ZENG Xiao-zhe, XU Ge, YUE Yun-qi

A tunable diode laser absorption spectroscopy technique using quantum cascade lasers and a movable open optical path system are proposed to realize on-line detection of SF6 gas in the leakage region. The optical path system is located around the interval of high-voltage combined appliances, and through the non-contact combination with the sensing system. The emission frequency range of the mid-infrared laser with injection current of 680 mA can cover the selected wavelength of SF6 gas at work temperature of 10℃. The precise background absorption of the second harmonic absorption is obtained by extracting and separating the internal environment of the large area laboratory module for several times. The leaked SF6 gas after diffusion equilibrium is measured by using the tunable laser sensor system with 10.55 μm. After subtracting the background absorption, the second harmonic absorption spectrum of the leaked SF6 gas was obtained. Research results show that under the open light path of 14.3 m, gas chromatography-thermal conductivity detector traceability of calibration data with tunable diode laser absorption spectroscopy technology testing consistency is well, the maximum deviation is 2.26%. The second harmonic signal amplitude and largest measuring concentration have a high fitting degree with fitting coefficient of 0.998, and SF6 volume concentration of the detection limit is 1.8×10-6. The study can provide a new detection method for SF6 gas leakage, so as to realize real-time online monitoring of SF6 gas under large area environment of high voltage combined appliances.

2019 Vol. 48 (10): 1030004-1030004 [Abstract] ( 22 ) PDF (4925 KB)   ( 14 )
Image Processing
Stable Object Tracking Method for Complex Infrared Ground Environment
Lü Jian, DENG Bo, QUE Long-cheng

Aiming at the problem of tracking failure and less robustness caused by background clutter, occlusion and object deformation in infrared object tracking, an infrared object tracking method combining tracking-learning-detection method and correlation filtering theory was proposed. Based on the traditional correlation filtering framework, the proposed method combines the direction gradient histogram feature and the luminance histogram feature to improve the model drift caused by slight deformation of the target. Aiming at the multi-peak response problem caused by background clutter and occlusion, the response of the target background area was punished, and the multi-modal detection mechanism of target and background response was established to achieve the target from coarse to fine positioning, and the adaptive learning rate was used to optimize the drift problem of the tracking model; Aiming at the problem that the object was severely occluded or the object was out of view, the global re-detection of the target was implemented to achieve the target re-capture. The experimental results show that the proposed algorithm effectively solves the object loss caused by background clutter and occlusion in the complex infrared ground environment. Based on the benchmark OTB-2015 and infrared video sequence test, compared with the mainstream correlation filtering tracking algorithms, the proposed algorithm improves the tracking accuracy and success rate by 5.6% and 4.1% respectively compared with the Long-term Correlation Tracking (LCT) algorithm; In the occlusion index test, the proposed algorithm improves the tracking accuracy and success rate by 4.6% and 6.1% respectively compared with the LCT algorithm.

2019 Vol. 48 (10): 1010001-1010001 [Abstract] ( 31 ) PDF (6585 KB)   ( 35 )
L1-2 Spectral-spatial Total Variation Regularized Hyperspectral Image Denoising
ZENG Hai-jin, JIANG Jia-wei, ZHAO Jia-jia, WANG Yi-zhuo, XIE Xiao-zhen

A model for Hyperspectral Image (HSI) restoration was proposed, which combines the L1 norm minimization of local patches and L1-2 Spatial-Spectral Total Variation (L1-2 SSTV) of global image. Firstly, the HSI was divided into local overlapping 3D patches, to reduce information loss caused by minimization of nuclear norm while improving local low-rank property. Secondly, the L1-2 SSTV regularization term with stronger sparse expression ability was proposed, to explore both spectral and spatial sparse prior simultaneously. Finally, the advantages of both worlds are combined, and a new HSI restoration model is proposed. The local norm is used to penalize spectrum low-rank term, and the L1-2 SSTV is used globally to constrain the spatial and spectral sparsity term of HSI, The model can not only effectively remove Gaussian noise, impulse noise, deadline and its mixture noise, but also reduce the dependence on the noise independent and identical distribution hypothesis, and can partially suppress the structure-related noise. Through a large number of experiments of simulated and real HSIs, and compared with the classical low-rank and total-variation-based restoration methods, experimental results were conducted to illustrate the advantage of the proposed method in HSI restoring, from visual/quantitative evaluations.

2019 Vol. 48 (10): 1010002-1010002 [Abstract] ( 30 ) PDF (9097 KB)   ( 19 )
Diffraction and Gratings
Fabrication of X-ray Absorption Gratings by Free Settling of Bismuth Nanoparticles
LEI Yao-hu, XU Gui-wen, LI Qiao-fei, WALI Faiz, LIU Xin, LI Ji, HUANG Jian-heng

To fabricate X-ray absorption gratings, deep reactive ion etching and wet etching are used to fabricate grating structures on silicon wafers, and a liquid carrier, which is wet with the surface of grating structure, is used to bring the bismuth nanoparticles into grating structures in a dense arrangement. Then, a grating structure with the period of 42 μm and depth of 150 μm is filled. To show the performance of the fabricated absorption grating, a comparison with the bulk bismuth grating obtained by micro-casting method is provided. Moreover, the relationship between the grating period and the filling compactness through filling grating structures with periods of 24 μm and 6 μm is found. The scanning electron microscopy micrographs show the effectiveness of free settling method for the large-period grating structures. However, for the structures with 6 μm period, the filling compactness is not satisfied. The results illustrate that bismuth nanoparticles that their diameters are much less than the width of grating structures should be selected for the small-period absorption gratings. Furthermore, nanoparticles-based free settling method lowers grating cost and technique threshold, and allows the fabrication of large-area absorption gratings.

2019 Vol. 48 (10): 1005001-1005001 [Abstract] ( 30 ) PDF (3613 KB)   ( 34 )
Fiber Optics and Optical Communications
Double Channel Phase-coded Microwave Signal System with Frequency Tunability
HAN Yi-shi, XIE Sheng-chao, FU Chen-yuan, ZHAO Bei-si, LEI Ke-ke

A photonic approach to generating two arbitrary and precisely π phase-shifted phase-coded microwave signals simultaneously with large frequency tenability in a single input case is proposed and demonstrated. The scheme is mainly consists of one dual-parallel Mach-Zehnder modulator and one polarization-maintaining fiber Bragg grating. After the laser inputs dual-parallel Mach-Zehnder modulator, the polarization-maintaining fiber Bragg grating and polarization beam splitter are combined to obtain two polarization orthogonal sidebands. One pair of side bands is modulated by the phase modulator and then coupled to the other pair. Finally, input them into two photodetectors to obtain high-frequency, low-noise encoded microwave signals. The simulation result shows that, by adjusting the frequency of the driving signal, a series of quadruplicated frequency phase-coded microwave signals of 5~100 GHz can be obtained. The recovered phase information and pulse compression ratio agree well with theoretical values, proving the good pulse compression performance of the proposed method.

2019 Vol. 48 (10): 1006001-1006001 [Abstract] ( 29 ) PDF (5189 KB)   ( 38 )
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