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    Locking of the Fringe Position and Period in Large-size Holographic Grating Exposure
    ZHANG Dong, ZHAO Cheng-qiang, XU Wen-dong, ZHANG Yi-bin, YAN Yu-qi
    Acta Photonica Sinica    2018, 47 (2): 205001-0205001.   DOI: 10.3788/gzxb20184702.0205001
    Abstract620)      PDF (4057KB)(2793)       Save

    The position and period of grating fringes will vary against the substrate during double beam interference exposure due to temperature variation, air flow, vibration and other factors in the fabrication of large-size holographic gratings. It will result in the decrease of grating contrast. The dynamic change of fringes was analyzed during large-size grating exposure. The Root-Mean-Square (RMS) errors of fringe translation and period in 3 hours are 1.87 and 1.20 period respectively. The corresponding simulative grating contrasts are 12.83% and 67.37% respectively. A fringe locking system composed of three monitoring subsystems, a computation and control subsystem and two piezo nanopositioners was set up. The translation and period of fringes can be locked at the same time. The groove shape and contrast of gratings are improved significantly after locking. The precision of this fringe locking system:the 3σ value of fringe translation and corresponding contrast are 0.009 period and 99.99% respectively; the RMS error of period change and corresponding contrast are 0.017 period and 99.77% respectively. This locking system satisfies the requirements of fringe stability for the exposure of large-size gratings.

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    Response and Electrical Characteristics of In0.53Ga0.47As/InP Avalanche Photodiode
    YUAN Zheng-bing, XIAO Qing-quan, YANG Wen-xian, XIAO Meng, WU Yuan-yuan, TAN Ming, DAI Pan, LI Xue-fei, XIE Quan, LU Shu-long
    Acta Photonica Sinica    2018, 47 (3): 304002-0304002.   DOI: 10.3788/gzxb20184703.0304002
    Abstract387)      PDF (5664KB)(1532)       Save

    In0.53Ga0.47As/InP Avalanche Photodiode (APD) with low dark current, wide-range response is prepared by molecular beam epitaxy and open-tube zinc diffusion method. The dark current is less than 10 nA at 0.95Vb (Vb is the avalanche breakdown voltage), and the capacitance density is as low as 1.43×10-8 F/cm2 when the bias voltage is -5 V. The response range of APD is 50 nW~20 mW and the responsibility is up to 1.13 A/W under 1 310 nm infrared laser at 30 V reverse bias voltage. The breakdown voltage and punch-through voltage are investigated by changing concentration of the charge layer and thickness of the multiplication layer. The result shows that the punch-through voltage increases linearly, conversely, the breakdown voltage decreases linearly with increasing concentration of the charge layer. Further, the punch-through voltage increases linearly and breakdown voltage also increases with increasing thickness of the multiplication layer, while the surface density of charge layer is 4.8×1012 cm-2. Through optimizing SAGCM-APD device structure, the APD device achieves a 25 V punch-through voltage and a 57 V breakdown voltage, with low dark current, and wide-range response characteristics.

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    Design and Fabrication of Rigid Fresnel Prisms for Complex Treatment of Strabismus in Children
    FU Ming-lei, HU Wei-jie, LE Zi-chun, Manko D. Y., Antonov E. E., Kryuchyn A. A., Petrov V. V.
    Acta Photonica Sinica    2017, 46 (11): 1123003-1123003.   DOI: 10.3788/gzxb20174611.1123003
    Abstract341)      PDF (4712KB)(1375)       Save

    In this paper, we present our design of a rigid Fresnel prism and derive the calculations of its transmittance and distortion. The transmittance of prisms made of different kinds of polymers and their distortion were numerically simulated. Simulation results showed that polymethyl methacrylate (PMMA) had a larger Abbe coefficient and a lower material absorption rate than polyvinyl chloride (PVC). Then, on the basis of the simulation, stamps for the prisms were machined using the diamond-cutting method; the surface roughness of the stamps reached class 14. We verified that low-cost prisms can be fabricated from PMMA using the thermopressing method under the conditions of 180℃ and 130 kg/cm2. A system was constructed to test the prism diopter (PD) values of the samples. Experimental results showed that the deviations between the calculated and actual PD values for 10Δ (low PD), 20Δ (medium PD), and 30Δ (high PD) prisms were 0.01Δ, 0.04Δ, and 0.02Δ, respectively. The PD deviations of the sample prisms all agreed with the Chinese tolerance standard for a medical prism. Hence, we verified that the rigid prisms fabricated in this study are sufficiently precise to reflect light and are a high-quality, low-cost solution for the treatment of strabismus in children.

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    Propagation of Near-infrared Light in Skin Tissue and the Design of Optical Fiber Detection Structure
    GAO Jing, HAN Guang, LU Qi-peng
    Acta Photonica Sinica    2018, 47 (1): 129002-0129002.   DOI: 10.3788/gzxb20184701.0129002
    Abstract955)      PDF (7209KB)(1246)       Save

    In order to study the propagation of near infrared light in the skin tissue, the human skin tissue model was established, including absorption coefficient, scattering coefficient, refractive index and anisotropy factor of epidermis, dermis and subcutaneous tissue in different incident wavelengths. Combining with the optical properties of skin tissue, the near infrared light propagation and distribution characteristics in skin tissue when subjected to different light source-detection distances from 1 000 nm to 1 900 nm were analyzed using Monte Carlo method. The results showed that photon path length and penetration depth increased with the increase of the source-detection distance, while normalized energy of diffuse light decreased with the increase of the source-detection distance. The source-detection distance was selected to be 0.45 mm. When the incident wavelength was 1 550 nm, the photon path length was 1.806 mm, the penetration depth was 0.467 mm, and normalized energy of diffuse light was 0.001 85. A kind of optical fiber detection structure was analyzed and designed according to Monte Carlo simulation results. The bifurcated fiber bundle was composed of 18 source fibers and 4 detection fibers, the distance of each fiber was 0.45 mm and just compactly adjacent. Finally, the diffuse light energy and illumination distribution collected by this optical fiber were simulated. Assuming that the incident light power was 1 W, the diffuse light power received by the detector was 0.598 mW. The results could provide a reference for the design of the portable detection spectra instrument.

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    Analysis the Influence of Temperature on the Wavelength Blue Shift of InP Laser
    XUE Zheng-qun, WANG Ling-hua, SU Hui
    Acta Photonica Sinica    2018, 47 (1): 125002-0125002.   DOI: 10.3788/gzxb20184701.0125002
    Abstract913)      PDF (1463KB)(1218)       Save

    The wavelength/temperature coefficient of AlGaInAs MQWs FP laser devices are measured by analyzing the wavelength changed with ambient temperature at the same heating power. Also, the wavelength of device changed with heating power under RT are measured, and the thermal resistance of device is calculated to be 183K/W. Then, the temperature stress storage experiment are carried out on the device, the results showed:a slowly increased of wavelength happened as the ambient temperature increased from 120℃ to 220℃; and, a obviously blue shifted of wavelength happened while the temperature arrived at 225℃, the wavelength of device shifted to 1 265 nm from 1 297 nm before experiment; as the temperature reached to 235℃, the wavelength of device shifted to 1 258 nm, and the mode spacing decreased from 0.92 nm before experiment to 0.84 nm, that the effective refractive index of optical mode increased from 3.66 to 3.77; finally, the device became failure as the temperature arrived at 240℃. The possible reasons were mainly due to the Al, Ga and In atoms in the waveguide, quantum well and barrier layers of epi-wafer migration and the composition of these layers changing under the high temperature stress. The results will more provide the foundation for failure mechanism analysis and performances improvement of device under high temperature.

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    Integrated Linear Variable Filter/InGaAs Focal Plane Array Spectral Micro-module and Its Wavelength Calibration
    WANG Xu-quan, HUANG Song-lei, YU Yue-hua, YE Jie-min, SHAO Xiu-mei, FANG Jia-xiong
    Acta Photonica Sinica    2018, 47 (5): 530001-0530001.   DOI: 10.3788/gzxb20184705.0530001
    Abstract671)      PDF (3138KB)(1184)       Save

    An integrated spectral micro-module with a linear variable filter and an InGaAs focal plane array was proposed. As the core light dispersing element, the linear variable filter was coupled with an InGaAs detector array. Compared with the grating spectrometer, the micro-module has compact structure and stable optical properties. The wavelength calibration method and its accuracy were proposed and validated experimentally. The spectral range of the module is from about 900 nm to 1 700 nm. The calibration accuracy is better than 1.3 nm and the spectral resolution is no larger than 1.25% of peak wavelength. Experimental results demonstrate that the method of wavelength calibration is feasible and accurate. The spectral micro-module can be widely used in field or on-line applications.

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    Optics/Digital Processing Co-design Method Based on Aberration Optional-correcting
    TAN Zheng, XIANG-LI Bin, LV Qun-bo, FANG Yu, SUN Jian-ying, ZHAO Na
    Acta Photonica Sinica    2018, 47 (5): 511001-0511001.   DOI: 10.3788/gzxb20184705.0511001
    Abstract853)      PDF (4277KB)(1151)       Save

    This paper is aiming at jointly optimizing the design and analysis of the optics and digital image processing for imaging systems. The influence of each aberration on the imaging sharpness is analyzed according to the Zernike polynomial model. A digital image processing algorithm is proposed for aberration correction, which is based on the variational bayesian framework and weighted bi-direction difference prior. Then the aberrations are divided into two categories:easy to digital correct and hard to digital correct, so an optics-digital processing co-design method can be established based aberration optional-correction. At last, a three-lens large aberration optical system is designed by the co-design method, its MTF value at the nyquist frequency is about 0.50; in contrast, a six-lens system is designed by traditional method, and its MTF value is about 0.53. These results show that the imaging quality of two system is similar, therefore, the proposed method would be capable of reducing the complexity of the optical system.

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    Study on Fabrication Technology and Properties of High Quality Perovskite Quantum Dots Film
    YU Bin-hai, YAN Cai-man, RAO Long-shi, TANG Yong, LI Zong-tao, CHEN Song-mao, LU Han-guang
    Acta Photonica Sinica    2018, 47 (2): 231001-0231001.   DOI: 10.3788/gzxb20184702.0231001
    Abstract900)      PDF (13085KB)(1142)       Save

    Perovskite quantum dots have attracted great attention due to their narrow emission spectrum, tunable spectrum and high quantum yield, however, their poor stability because of the sensitivity of water and oxygen molecules limits their application. Polymethyl methacrylate (PMMA) and polystyrene-polyethylene-polybutene-polystyrene block copolymer (SEBS) were selected as two kinds of polymer materials to study their perovskite quantum dots film performances. The high-quality perovskite quantum dots films were fabricated by one-step package method. The decay rate of PMMA perovskite films was about 4 times and 6 times that of SEBS films under continuous 365 nm UV excitation and LED remote package, which indicated SEBS perovskite films had better stability than PMMA. Furthermore, the stability of SEBS perovskite films in air and water was studied. Compared with the 18% recession after about 4 h of the perovskite quantum dots solution, it was found that SEBS perovskite films in the air and water about 18% degradation extended to 55 h and 240 h, indicating that SEBS package enhanced the stability of the perovskite quantum dots, which has great significance to the application of perovskite quantum dot package in the future.

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    Development of Wavelength Separation Coating in 1 064 nm Laser and Far-infrared Common-window Imaging System
    FU Xiu-hua, SUN Bing, ZHANG Jing, XIONG Shi-fu, GUO Kai, JIANG Hong-yan
    Acta Photonica Sinica    2017, 46 (12): 1231001-1231001.   DOI: 10.3788/gzxb20174612.1231001
    Abstract895)      PDF (2628KB)(1079)       Save

    According to the technical requirements of the laser and far infrared common-window imaging system, a wavelength separation coating was developed, which aimed to separate the laser and far infrared light through a common window, that is, 1 064 nm laser reflected, 8~14 μm far infrared light transmitted. By analyzing the microstructure of the films, the refractive index changes of the films before and after moisture absorption were studied. The structure of the films was optimized by combining the optical film theory. On the basis of studying the stress of the film, the film thickness was optimized and the film firmness was improved. The average transmittance of the wavelength separation coating in the bands of 8~12 μm、12~14 μm are 97.1%, 90.1% and the reflectivity of 1 064 nm is 99.71%. The separation coating can meet the technical requirements of the imaging system for a long time in various military outdoor environments.

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    Dispersion Adjustment Effect of the Chirped Fiber Gratings in Chirped Pulse Amplification System by Continuous Linear Temperature Gradient Field
    TANG Shu-kui, YANG Zhi, LI Feng, LI Qiang-long, WEI Yu-feng, YANG Xiao-jun, WANG Yi-shan
    Acta Photonica Sinica    2018, 47 (5): 514005-0514005.   DOI: 10.3788/gzxb20184705.0514005
    Abstract630)      PDF (2985KB)(1036)       Save

    According to the temperature tunability of chirped fiber grating, a new kind of dispersion compensation method was proposed, which make chirp fiber grating in a continuous linear temperature gradient field. The dispersion of chirped fiber Bragg grating is fine-tuned by adjusting temperature difference between the ends of the fiber Bragg grating. The dispersion mismatch in chirped pulse amplification system, which is based on the chirped fiber Bragg grating as pulse stretcher and chirped volume Bragg grating as pulse compressor, can be continuously compensated, and the feasibility of this method is verified by experiment. The experimental results show that the application fields, when the temperature difference of the continuous temperature gradient along the chirped fiber Bragg grating continuously changes from 0℃ to 50℃, the dispersion mismatch between the stretcher and compressor can be continuously adjusted, thereby eliminating the tedious pulse width optimization steps. The gradient of the continuous linear temperature field is reported for the first time to fine-tune the dispersion mismatch in chirped pulse amplification system that uses the chirped fiber Bragg grating as pulse stretcher and chirped volume Bragg grating as pulse compressor.

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    Generation of Hybridly Polarized Vector Beams by Manipulating Pancharatnam-Berry Phase
    XU Zhao-xin, HUANG Xiu-zhang, HUANG Pan-li, AI Yu-qian, ZHANG Chen, CHEN Huan, YI Xu-nong
    Acta Photonica Sinica    2018, 47 (1): 126002-0126002.   DOI: 10.3788/gzxb20184701.0126002
    Abstract514)      PDF (4834KB)(1012)       Save

    A method for generating hybridly polarized vector beams by manipulating Pancharatnam-Berry (PB) phase is proposed. According to the law of optical axis varying with the spatial coordinates, a PB phase element is used to manipulate the PB phase and generate vector beams with local linear polarization. When the vector beam is incident to a quarter-wave plate, a hybridly polarized vector beam is obtained. By measuring the Stokes parameter, the polarization distribution of the output light field is reconstructed. The experimental results show that the output hybridly polarized field contains all polarization states on the longitude of Poincaré sphere perpendicular to S3 axis when input wave is linearly polarized light with polarization angle θ0=0. The output hybridly polarized field contains all polarization states on the longitude of Poincaré sphere perpendicular to S3 axis when input wave is linearly polarized light with polarization angle θ0=0. When the polarization angle θ0=π/2, the output hybridly polarized field includes all polarization states on the longitude of Poincaré sphere perpendicular to S1 axis.

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    Fail-safe Optimal Design of Uniform Illumination for UV-LED Array
    CAI Wen-tao, YIN Shao-yun, SUN Xiu-hui, XIANG Yang, DU Chun-lei, YANG Ruo-fu
    Acta Photonica Sinica    2018, 47 (4): 422002-0422002.   DOI: 10.3788/gzxb20184704.0422002
    Abstract502)      PDF (3302KB)(959)       Save

    For weakening or eliminating the effect on uniformity, the method of uniform light accumulation based on fly-eye lens was presented. At first, illumination uniformity is designed for one LED. Then the same uniform light spot can be generated on the target surface from every LED,according to the study of LED position error. Next, An exposure light source is designed by a simulation optimization software. The maximum illuminance is 18.2 mW/cm2 while the uniformity is 86.9%, which meeting the exposure requirements fully. At last, an experiment is made to test the illumination uniformity with the method of blocking LEDs. The result shows that a few invalid LEDs cause less than 1% decease of uniformity. Even half of invalid LEDs lead to a result that uniformity declines by less than 5%. Thus, this method better suits actual manufacture than others by maintaining illumination uniformity for a long period.

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    Design Method for the Near-field Diffractive Optical Elements with Large Diffraction Angle Based on the Rayleigh-Sommerfeld Diffraction Theory
    LI Jing, WU Peng, YANG Zheng, ZHENG Qian-ying, LI Tao-jie, XIANG Yang, DU Chun-lei, YIN Shao-yun
    Acta Photonica Sinica    2017, 46 (11): 1122003-1122003.   DOI: 10.3788/gzxb20174611.1122003
    Abstract590)      PDF (3802KB)(952)       Save

    A novel method is presented for designing the near-field diffraction optical element (DOE) with large diffraction angle based on the Rayleigh-Sommerfeld diffraction theory. The relation of space position of sampling points between the DOE surface and the receiving surface is studied. The forward and inverse diffraction calculation methods without far-field and paraxial approximation are used. The design method of near-field DOE with large diffraction is obtained by modifying the traditional Gerchberg-Saxton algorithm. Compared with the traditional design method and the existing large diffraction angle design method, the proposed method shows significant advantages on designing the same "田" Shape target pattern. The simulation results show that the target pattern in the near field with large diffraction angle is accurately reconstructed by using the proposed method, while the reconstructed light fields with the other two methods shows dramatical distortion or fuzziness.

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    Mode Multiplexer and Demultiplexer Utilizing Tapered Couplers
    YANG Tian-jun, LI Shi-qi, WANG Peng-jun, CHEN Wei-wei
    Acta Photonica Sinica    2017, 46 (11): 1123002-1123002.   DOI: 10.3788/gzxb20174611.1123002
    Abstract428)      PDF (2440KB)(922)       Save

    In this paper, we design and demonstrate a mode (de)multiplexer using tapered couplers on a silicon-on-insulator substrate by commercial 0.18 μm complementary metal-oxide-semiconductor compatible processes. By controlling the width of a tapered waveguide, the mutual conversion between the fundamental mode in the tapered waveguide and the high-order mode in the multimode straight waveguide can be realized due to the matching of modal effective indexes. For the multiplexing and demultiplexing of the TE0, TE1 and TE2 modes, the fabricated device, which is composed of a mode multiplexer, a multimode straight waveguide, and a mode demultiplexer, exhibits crosstalk lower than -8.05 dB within a bandwidth from 1 530 nm to 1 570 nm. The crosstalk is less than -16.43 dB for the multiplexing and demultiplexing of the TE0 and TE2 modes.

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    Characterizing the Absorption of Terahertz Wave by Graphene under the Excitation of Different Luminous Power
    ZHANG Wen-tao, LI Gan, ZHAN Ping-ping, LI Yue-wen, ZHANG Yu-ting
    Acta Photonica Sinica    2018, 47 (5): 516005-0516005.   DOI: 10.3788/gzxb20184705.0516005
    Abstract398)      PDF (5047KB)(906)       Save

    The transmissivity and conductivity of the few-layer graphene with 600 nm CW laser and two substrates are measured and analyzed, based on terahertz time-domain spectroscopy and the Drude model. In this study, the absorption of terahertz signal is obviously enhanced through the graphene on high-resistivity silicon or the absorption of terahertz signal is slightly decreased through the graphene on PET (Polyethylene terephthalate) with the excitation of external laser. At 0.5 THz, the conductivity of the graphene on high-resistivity silicon is increased by 7 times or the conductivity of the graphene on PET is felled to 77%, compared to that without external laser. Meanwhile the experiments verify that the conductance in the few-layer graphene appears as the linear superposition of per layer among the THz waveband.

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    Photoelectric Controllable Frequency Selective Surface
    WANG Jun, SUN Yan-jun, JI Xue-song, WANG Li, WANG Yue, LENG Yan-bing
    Acta Photonica Sinica    2018, 47 (3): 324002-0324002.   DOI: 10.3788/gzxb20184703.0324002
    Abstract458)      PDF (2996KB)(897)       Save

    To achieve the photoelectric controllable characteristics of Frequency Selective Surface (FSS) resonant frequency, a photoelectric controllable FSS is put forward in this paper. The photoconductive thin film is used to control the change of the structure size of FSS, so as to realize the controllability of FSS. This thesis starts from the theory of the photoconductive thin film and the principle of the characteristics that FSS can select frequency. The CST software was used to simulate three kinds of FSS:"tripole" slot-element, "circular" slot-element, "tripole" patch-element, and get the selecting frequency characteristics of different structure sizes. The simulation result shows that, with the changing structure size, the center resonant frequency of the FSS changes from 18 GHz, 25 GHz, and 20.5 GHz to 20.5 GHz, 29 GHz, and 16.5 GHz respectively. Finally, the metallic FSS with the unchanged structure size, and the FSS of the metal and the photoconductive thin film combined, were fabricated by coating, etching, electron beam evaporation and so on. Test the samples and the result shows that the center resonant frequency changes from 18 GHz, 24 GHz, 20 GHz into 20 GHz, 28 GHz, 17 GHz. Compared with the simulation results, the trend is about the same. Ultimately, we can draw the conclusion:in this way, not only can we realize the characteristic of controlling the center resonant frequency, but also we can achieve the conversion of slot-element or patch-element in the structure of FSS.

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    Cited: Baidu(1)
    Reduction of Graphene Oxide by Laser with Different Wavelengths
    XIE Lei, LEI Xiao-hua, TAN Xiao-gang, LIU Xian-ming, DENG Yi-jun, CHEN Wei-min
    Acta Photonica Sinica    2018, 47 (4): 431003-0431003.   DOI: 10.3788/gzxb20184704.0431003
    Abstract537)      PDF (3234KB)(894)       Save

    The 488 nm, 518 nm and 637 nm lasers in visible wavelength band were used to carry out the light reduction experiment on the graphene oxide samples. Meanwhile the transmittance and resistance of reduced graphene oxide were measured in real time to investigate effect of laser with different wavelengths on reduction of graphene oxide. The results show that the transmittance and resistivity of reduced graphene oxide appear different variation under different wavelengths laser irradiation. When 488 nm laser is used, the sample can be reduced though under the condition of low power density, and the reduction process is in accordance with the photochemical reaction. When using 518 nm and 637 nm laser, only when the laser power density is greater than a certain threshold, can the graphene oxide be reduced; longer the laser wavelength, higher the power threshold; and the reduction process conforms to photothermal reaction. The results can pave a way for the improvement of the patterning process of graphene film.

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    Effect of Two-color Laser Wavelength on Intense Terahertz Generation
    CHEN Ze-you, FAN Wen-hui, CHEN Xu, DING Ling, SONG Chao
    Acta Photonica Sinica    2017, 46 (12): 1214003-1214003.   DOI: 10.3788/gzxb20174612.1214003
    Abstract462)      PDF (3254KB)(889)       Save

    The effect of the two-color laser wavelength on intense terahertz generation was studied based on the transient photocurrent model. Theoretical calculation proves that the terahertz signal will increase with the increase of laser wavelength, and this trend will not vary with the variation of the pulse intensity, the pulse duration, the laser phase and the intensity ratio of the two-color laser. The distribution of terahertz spectrum will not change with the variation of the laser wavelength. Furthermore, the influence of laser wavelength on terahertz generation is analyzed, and the physical mechanism of this effect is explained by the free electron density and the drift current density.

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    Research on Ladder-type Compensation Filter Based on Solar Simulator
    FU Xiu-hua, YANG Jin-ye, LIU Dong-mei, ZHANG Jing, GUO Kai
    Acta Photonica Sinica    2017, 46 (11): 1123001-1123001.   DOI: 10.3788/gzxb20174611.1123001
    Abstract571)      PDF (1550KB)(886)       Save

    The solar simulator is a device that uses artificial light to simulate sunlight, as an important component of the solar simulator, the accuracy of the filter spectral requirements are getting higher and higher. In this paper, a step compensation filter with five different spectral requirements in the 0.4~1.1 μm band is designed by establishing a mathematical model and introducing a new evaluation function. In the process of film preparation, the least squares method was used to fit the experimental data, and the relationship between the residual deposition amount and the thickness of the film was found, which solves the spectral effect of the residual deposition on the film, and the film finally meets the requirements.

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    Denoising Lidar Signal Based on Ensemble Empirical Mode Decomposition and Singular Value Decomposition
    CHENG Zhi, HE Feng, JING Xu, ZHANG Si-long, HOU Zai-hong
    Acta Photonica Sinica    2017, 46 (12): 1201003-1201003.   DOI: 10.3788/gzxb20174612.1201003
    Abstract490)      PDF (4852KB)(876)       Save

    In order to enhance the Signal-to-Noise Ratio (SNR) of Differential Column Image Motion lidar (DCIM lidar) detetion, a hybid denoising method which combines Ensemble Empirical Mode Decomposition (EEMD) and singular value decomposition(SVD) is proposed.The multilayer mode components are obtained from EEMD firstly. The difference of cross-correlation coefficients among these mode components is then utilized to determine the main noises which should be removed. The residual noises contained in mode components are identified by SVD and then the useful signal is extracted. Both the EEMD-SVD and EEMD methods are used to denoise the simulation signals and measured DCIM lidar signals. When the standard deviation of simulated noises is between 0.05 and 0.2, the signal-to-noise ratio(SNR) of retrieved turbulence profile with EEMD-SVD denoising is increased by 2.718 7 dB to 6.921 5 dB and the SNR of corresponding EEMD method is increased by 0.168 4 dB to 3.555 4 dB compared with the retrieved profile without denoising. Turbulence profiles retrieved from the undenoised and denoised DCIM lidar measurements and radio-sounding balloons are also compared at two typical time periods. It is found that the maximum SNR of turbulence profiles can separately be increased by 2.526 5 dB and 2.155 6 dB for EEMD-SVD and EEMD method compared with undenoising retrieval profile. The results indicate that the noise reduction effect of EEMD-SVD is superior than EEMD,which it is able to identify and reduce the noises more effectively.The SNR of original signal is greatly improved through EEMD-SVD method, thereby the retrieved atmospheric turbulence profile is achieved more accurately.

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