Journals >Acta Photonica Sinica
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2016
Volume: 45 Issue 11
26 Article(s)
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Research Article
Broadband Terahertz Absorber Based on Three-layer Gratings
GUO Jian-qin, XU De-gang, LIU Peng-xiang, WANG Yu-ye, ZHONG Kai, and YAO Jian-quan
A terahertz absorber composed of three-layer micro-structure gratings was designed based on the effective medium theory and the theory of multi-layer antireflection coating. The absorber was designed on the heavily boron doped silicon. By using the finite-difference time-domain method, the influence of the grating periA terahertz absorber composed of three-layer micro-structure gratings was designed based on the effective medium theory and the theory of multi-layer antireflection coating. The absorber was designed on the heavily boron doped silicon. By using the finite-difference time-domain method, the influence of the grating period, width and depth on the reflection coefficient was analyzed. The numerical simulation results show that, in the range of 0~3 THz, more than 98% terahertz absorption can be achieved with a bandwidth of 1.3 THz and over 95% terahertz absorption can be obtained with a bandwidth of 2.1 THz. The high performance of the absorber was explained by the rigorous coupled-wave theory, which suggests that the interaction among the different grating diffraction modes reduces the reflection of the incident wave and increases the absorption rate of the absorber. By structural parameter optimization, the absorber can achieve more than 95% broadband terahertz absorption in the range of 0.6~6 THz. The absorber may be a valuable candidate for use in Terahertz imaging and detecting..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1105001 (2016)
Improved Chin-Shifrin Algorithm in the Measurement of Particle Sizing Used by Fraunhofer Diffraction Method
CHEN Quan, LIU Wei, YANG Lin, WANG Ya-jing, and SHEN Jin
In the measurement of particle size by Fraunhofer diffraction method based on a linear CCD, the Chin-Shifrin inversion algorithm can lead to false peaks in the inversion of Particle Size Distribution (PSD). To overcome this phenomenon of the algorithm, a rectangular window function was proposed and introduced in this aIn the measurement of particle size by Fraunhofer diffraction method based on a linear CCD, the Chin-Shifrin inversion algorithm can lead to false peaks in the inversion of Particle Size Distribution (PSD). To overcome this phenomenon of the algorithm, a rectangular window function was proposed and introduced in this algorithm. The midpoint and boundary of the window function were determined by analyzing the relationship between particle size and its minimum value of derivative of the diffraction light intensity. The inverted PSD was truncated by superposing the window function to remove the false peaks and enhance the accuracy of the inverted PSD. The results of the inverted PSDs obtained by using different algorithms were compared by measuring two types of standard materials respectively. Experimental results show that, the improved Chin-Shifrin algorithm can effectively eliminate the false peak distributions in the inverted PSD. The relative error of the measuring results is less than 3%, and the repeatability is no more than 4%..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1105002 (2016)
Flow/Pressure/Temperature Simultaneous Measurement Technology in Hydraulic System Based on FBG
LIU Chun-tong, ZHANG Zheng-yi, LI Hong-cai, HE Zhen-xin, ZHAO Xiao-feng, and WU Rong-jing
In view of the sensor problems, such as insufficient function, large size, low measurement accuracy, existing in the conventional detection methods for the hydraulic system, a compound sensor based on fiber Bragg grating was designed. On the basis of the integration of target-type flow sensor, the sensor combines with In view of the sensor problems, such as insufficient function, large size, low measurement accuracy, existing in the conventional detection methods for the hydraulic system, a compound sensor based on fiber Bragg grating was designed. On the basis of the integration of target-type flow sensor, the sensor combines with fiber Bragg grating temperature and pressure sensor simultaneously, so the flow, pressure and temperature of hydraulic system can be measured simultaneausly. Based on theoretical analysis of each parameter sensing model, the sensor structure was designed, and the sensor was produced in practice. The equipments such as hydraulic pressure colligation test system were used for the sensor performance testing and calibration. The results show that, the flow measurement sensitivity of the sensor is 0.049 L/s, the pressure sensor measurement sensitivity is 28.4 pm/Mpa, the temperature sensor measurement sensitivity is 14.9 pm/℃, and the sensor design reasonableness is verified. Meanwhile, the temperature measuring function of the sensor can be used as a reference fiber Bragg grating, when the fiber Bragg grating flow and pressure sensor are used in measurement, which can overcome the crossed sensitivity with temperature, and improve the sensor adaptability..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106001 (2016)
Influence of Non-Kolmogorov Turbulence on the Rayleigh Range and Turbulence Distance of the Radial Partially Coherent Array Beams
KE Xi-zheng, ZHANG Ya, and CHEN Wei
Based on the generalized Huygens-Fresnel principle and the non-Kolmogorov spectral model, the expressions for the Rayleigh range zR and the turbulence distance zT of radial partially coherent Gaussian-Schell model array beams of the free space optics system propagating through non- Kolmogorov turbulence were derived. ABased on the generalized Huygens-Fresnel principle and the non-Kolmogorov spectral model, the expressions for the Rayleigh range zR and the turbulence distance zT of radial partially coherent Gaussian-Schell model array beams of the free space optics system propagating through non- Kolmogorov turbulence were derived. And the expressions were used to analyze numerically the changes of the Rayleigh range and the turbulence distance with turbulence parameters and beams parameters. The results show that for both coherent and incoherent combinations, the dependence of zR and zT of the radial partially coherent Gaussian-Schell model array beams on generalized parameter α is not monotonic. When α=3.11, zR and zT reach their minima, and this means that the beams spreading is largest. For the coherent combination of beams spreading is smaller than that for the coherent combination, but it is larger affected by turbulence; For coherent combinations, the larger the radial distribution radius r0, the larger the Rayleigh range zR and turbulence distance zT of the combined beam, but incoherent combinations is not affected; for both coherent and incoherent combinations, the number of sub-beams has no influence on the Rayleigh range and the turbulent distance of the combined beam; When beams coherent parameter β is small enough and wavelength λ is large enough, the influence of turbulence on zR can be ignored..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106002 (2016)
Liquid Crystal Infiltrated Tellurite Photonic Crystal Fiber Polarization Rotator
LIU Zhao-lun, AN Jing, HANG Ying, and BI Wei-hong
By employing the liquid crystal refractive index changes induced by an applied electric field, a polarization rotator was proposed based on liquid crystal infiltrated tellurite photonic crystal fiber. The mode field distribution of the fiber fundamental mode and the influence on polarization rotation of some parametersBy employing the liquid crystal refractive index changes induced by an applied electric field, a polarization rotator was proposed based on liquid crystal infiltrated tellurite photonic crystal fiber. The mode field distribution of the fiber fundamental mode and the influence on polarization rotation of some parameters were simulated by using full vector finite element method. The results show that, this polarization rotator has a high work efficiency, low crosstalk and short conversion length. With the wavelength of 1.55 μm and the polarization angle of 45°, the values are 99.95%, －32.84 dB and 197 μm, respectively. The conversion length of the fiber becomes longer, when the thin wall thickness of grapefruit photonic crystal fiber is increasing or the temperature is decreasing. While the working wavelength is increasing, the conversion length of the fiber becomes shorter. The liquid crystal infiltrated tellurite photonic crystal fiber has a good polarization rotation performance, offering a reference for the design of polarization rotator, which is useful for making compact and diverse polarization rotation devices..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106003 (2016)
Temperature Sensing System Based on Brillouin Optical Time Domain Reflectometer with Broad-band Laser and Self-heterodyne Detection
LI Xiao-juan, LI Yong-qian, HE Yu-jun, and ZHANG Li-xin
To simplify the system structure and reduce the effect of coherent Rayleigh noise on system performance, a temperature sensing system based on Brillouin optical time domain reflectometry by employing broad-band laser and self-heterodyne detection of Rayleigh and Brillouin scattering was proposed. The principle of self-To simplify the system structure and reduce the effect of coherent Rayleigh noise on system performance, a temperature sensing system based on Brillouin optical time domain reflectometry by employing broad-band laser and self-heterodyne detection of Rayleigh and Brillouin scattering was proposed. The principle of self-heterodyne detection of Rayleigh and Brillouin scattering was analyzed, and the relationships of Brillouin frequency shift and self-heterodyne detection signal power with temperature and strain were studied. A temperature sensing system based on Brillouin optical time domain reflectometry by employing broad-band laser and self-heterodyne detection was designed and constructed, the power spectrum of self-heterodyne detection signal along the sensing fiber at room temperature and the power spectra of the heated fiber at different temperature were obtained. The linear increase relationships of Brillouin frequency shift and change in relative self-heterodyne detection signal power with temperature were demonstrated. The temperature coefficients of Brillouin frequency shift and change in relative power were experimentally obtained to be 1.07±0.01 MHz/℃ and (0.37±0.09)% /℃. The results of this study can provide a theoretical and experimental basis for the simultaneous measurement of temperature and strain of Brillouin optical time domain reflectometer sensing system based on self-heterodyne detection of Rayleigh and Brillouin scattering..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106004 (2016)
Optical-spectrum Characteristics of a Biconical Fiber Bragg Grating
ZHAO Hong-xia, CHENG Pei-hong, DING Zhi-qun, BAO Ji-long, JIANG Peng, and LI Yin-jie
Using transfer matrix method and finite element method, the influences of fabrication and structure factors, such as grating period, modulation depth, diameter of waist and length ratio in different regions, on the spectral characteristics of the biconical fiber Bragg grating were analyzed. The simulation results demonUsing transfer matrix method and finite element method, the influences of fabrication and structure factors, such as grating period, modulation depth, diameter of waist and length ratio in different regions, on the spectral characteristics of the biconical fiber Bragg grating were analyzed. The simulation results demonstrate that when other grating factors remain unchanged, the reflection spectrum of the biconical fiber Bragg grating red-shifts with the increasing of grating period. This change trend is in accord with that of the uniform fiber Bragg grating. However, when the modulation depth is enhanced, the two main peaks does not shift, but the number of secondary peaks between the two main peaks increases and intensity is enhanced. Moreover, with the decrease of the cone waist diameter, more cladding modes are excited, and more interference peaks with enhanced intensity are observed. When the grating length is kept at 1 cm, the length ratios between waist region, standard grating region and gradient grating region will impact the number and the amplitude of the secondary peaks directly. With the increase of the gradient grating region length, the number of secondary peak decreases but the amplitude increases. In a word, by properly designing the grating factors, the biconical fiber Bragg grating can be widely used in multi-parameter sensors, multi-channel filters, multi-channel semiconductor laser, dispersion compensation and OADM..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106005 (2016)
Temperature-insensitive Curvature Sensor Based on a Peanut-shape Structure and a FBG
WANG Zhao-wei, LU Shi-li, SUN Ming-ming, and JIN Yong-xing
A temperature-independent curvature sensor was presented for solving the high cost of wavelength demodulation and cross sensitive problem. The sensor consists of a fiber Bragg grating spliced after a peanut-shaped fiber, and it is reflected light intensity demodulation. With the broadband light entering the peanut-shapA temperature-independent curvature sensor was presented for solving the high cost of wavelength demodulation and cross sensitive problem. The sensor consists of a fiber Bragg grating spliced after a peanut-shaped fiber, and it is reflected light intensity demodulation. With the broadband light entering the peanut-shaped structure, the cladding mode is excited, being reflected by the FBG, the reflected core mode is excited by the peanut-shape structure again making several ranking cladding modes, which interference with the core mode. The reflected spectrums not only consist of the FBG peak but also consist of several resonant peaks, the shorter the wavelength is, the higher ranking of the cladding mode is. The experiment results show that the intensity of the reflected resonant peaks decreases from 2.260×10－7 mW to 1.501×10－7 mW with the curvature increases from 0.669 0 m－1 to 1.250 0 m－1. The average curvature sensitivity is －1.306×10－7 mW/ m－1. Temperature test on the structure shows that the power of the reflected cladding modes made little change with temperature increases from 25℃ to 75℃. The proposed curvature sensors is less expensive and the peanut-shaped structure has the feature of easy making and high mechanical strength etc..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106006 (2016)
Study of High-precision Dynamic Optical Fiber Strain Sensing
LIU Chong-chong, ZOU Xiang, and ZHOU Zheng-xian
Traditional fiber strain sensing technologies can not meet the properties of high precision, good environment adaptability and realize dynamic strain sensing stably at the same time. In order to solve this problem, an optical interference principle was adopted to realize optical fiber strain sensing in this paper, a kiTraditional fiber strain sensing technologies can not meet the properties of high precision, good environment adaptability and realize dynamic strain sensing stably at the same time. In order to solve this problem, an optical interference principle was adopted to realize optical fiber strain sensing in this paper, a kind of high-precision dynamic optical fiber strain sensing system with a good environment adaptability based on an interference structure was designed. The system can be used to detect strain stably based on cross correlation coefficient of swept interferometer signal. This paper also proposes the dynamic detecting method that significantly increases practical detection range to overcome the drawback that the system can only detect small strain and realize strain sensing dynamicly. The cubic spline interpolation algorithm was used to improve the accuracy of detection of small strain. Theoretical analysis and simulation experiments show that, the precision of measurements after interpolation is 2.3 times which is higher than that before interpolation, and the maximum measurement error of strain is only 9 nε when the signal to noise ratio is 15 dB..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1106007 (2016)
Out-of-plane Displacement Measurement Using Optical Vortex Phase Shifting
SUN Hai-bin, and SUN Ping
In order to realize the digital control of phase shifting in Electronic Speckle Pattern Interferometry (ESPI), a method for out-of-plane displacement measurement by applying phase shifting based on optical vortex was proposed. In the experiment, vortex beam is generated by a Reflective Liquid Crystal Spatial Light ModuIn order to realize the digital control of phase shifting in Electronic Speckle Pattern Interferometry (ESPI), a method for out-of-plane displacement measurement by applying phase shifting based on optical vortex was proposed. In the experiment, vortex beam is generated by a Reflective Liquid Crystal Spatial Light Modulator (LC–SLM), and the phase shifts are obtained by rotating the vortex beam around its axes. Vortex beam which is used as reference light interferes with object light, and the out optical field is captured by a CCD camera. Four speckle patterns with phase-step π/2 are captured by the CCD before and after the deformation, respectively. The phase difference of the deformed object is obtained by unwrapping. Experimental results demonstrate the efficacy of the proposed method for out-of-plane displacement measurement..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1112001 (2016)
Integrated Measurement System with Galileo Telescope Combined with Cylindrical Lens
LIU Ai-min, GAO Li-min, XIAO Mao-sen, LU Wei-guo, and WANG Hai-xia
To achieve azimuth and height measurement of a slowly moving point in a certain distance and wide field of view, a combined long-focal-length cylindrical lens measurement system was built. A point shape reticle, a long-focal-length optical system formed by a Galileo telescope combined with cylindrical lens and two orthTo achieve azimuth and height measurement of a slowly moving point in a certain distance and wide field of view, a combined long-focal-length cylindrical lens measurement system was built. A point shape reticle, a long-focal-length optical system formed by a Galileo telescope combined with cylindrical lens and two orthogonal linear array CCD were utilized. There isn’t a real middle image plane in the combined long-focal-length optical system with a relatively short optical length. The front part of the system is a Galileo telescope, and its focal power is approximate to 0. Within a measurement range, some parameters, such as the value of the angular magnification and diameter of the front part, should be properly selected, making the linear image from different field orthogonal to the two linear CCD. Through targeted lens system design optimization, proper selection of merit function, and tolerance analysis of the alignment and measurement principle, the acurracy of azimuth measurement of this system is less than ±2.5″, within field of view of 1.5°×1.5° , at the measurement distance of 10 m, additionally with relatiely small system length, and relatively loose tolerance. The proposed system can solve the problem of the limited size of light source cooperation target, making a low cost and large size photo-electronic detector..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1112002 (2016)
Development of an Astronomical Modularized CCD Universal Controller
ZHANG Yu-heng, WEI Ming-zhi, SONG Qian, and YAN Yi-hua
To meet the increasing demands of large mosaic CCD cameras from astronomical observation, an modularized CCD universal controller was developed. The modularization design is based on the principle that the system can be extended easily to drive multiple CCDs. Great efforts are exerted to reduce the system noise of the To meet the increasing demands of large mosaic CCD cameras from astronomical observation, an modularized CCD universal controller was developed. The modularization design is based on the principle that the system can be extended easily to drive multiple CCDs. Great efforts are exerted to reduce the system noise of the controller. A fully digital structure is chosen therefore the clocking and biasing can be tuned to control different kinds of CCDs and all the controlling data can be monitored remotely. With efforts, the system's readout noise reaches 2.61e-, dynamic range 16 bit, nonlinearity less than 1%, and these parameters meetthe criteria required for most of the astronomical observations for the-time-being. With this controller, a CCD camera is constructed to test a spectrogaph which is designed to work from 102 nm to 320 nm for space astronomical observation and the spectrums of helium and deuterium lines of the 121.5, 164, 193, 205, 218.6, 273.3 and 294.5 nm are acquired..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1112003 (2016)
Comparison between the Regularization Algorithm and the Chahine Algorithm in Inversions of Scattering Measurement Data of the Noisy Dynamic Light
XIU Wen-zheng, SHEN Jin, XIAO Ying-ying, XU Min, WANG Ya-jing, and YIN Li-ju
In this paper, two kinds of commonly used particle size inversion methods, regularization algorithm and Chahine algorithm, were used to inverse the simulated dynamic light scattering data of the unimodal distribution of 90nm and 250nm, the bimodal distribution of 50nm and 200 nm, and the bimodal distribution of 100 nm In this paper, two kinds of commonly used particle size inversion methods, regularization algorithm and Chahine algorithm, were used to inverse the simulated dynamic light scattering data of the unimodal distribution of 90nm and 250nm, the bimodal distribution of 50nm and 200 nm, and the bimodal distribution of 100 nm and 300 nm of the particles in submicron region, and measured the dynamic light scattering data of 105nm and 300nm particles, for comparing the noise effects of the two algorithms. The inversion results show that, the noise level is one of the key factor can restrict the accurate inversion for particle size measurement. The accuracy of inversion results decreases with the increase of the noise level, and when the noise level increase to a certain threshold value, the meaningful inversion results will not be obtained. Different inversion methods have different anti-noise ability, but there is no significant difference of the inversion results when noise level is very low. With the increase of the noise level, the retrieval results show a substantial difference: regularization method can effectively restrain the noise influence by the appropriate choice of the regularization parameter, which shows a better anti noise capability than Chahine algorithm. Compared with the Chahine algorithm, the regularization method, despite the need for regularization parameter setting, it does not need to assume the initial distribution. Therefore, it is recommended to use in noisy environment..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1112004 (2016)
Extraction Efficiency and Polarization Induced by Photonic Crystal Structure on GaN-based Blue LED
LU Li-feng, and YE Zhi-cheng
In order to improve the extraction efficiency, photonic crystal was generated on the ITO current spreading layer of GaN-based blue LED. By using the finite difference time domain method, the relationship between the structural parameters of photonic crystal and extraction efficiency was simulated. The optimization enheIn order to improve the extraction efficiency, photonic crystal was generated on the ITO current spreading layer of GaN-based blue LED. By using the finite difference time domain method, the relationship between the structural parameters of photonic crystal and extraction efficiency was simulated. The optimization enhencement results of 27.93% were obtained on the photonic crystal with cycle of 300nm, duty of 60% and etching depth of 200nm. Point source location varied in a photonic crystal lattice cycle was investigated in the finite difference time domain method simulation to get the correction extraction efficiency by fitting the simulations. Using the effective medium theory to get the effective refractive indexes, extraction efficiencies of both TE and TM mode polarization were calculated according to Fabry-Perot thin-film interference model. The maximum difference between the TE and TM light out-coupling was 1.442, and the light source with high polarization contrast was obtained. The proposed device can be applied in the LED back-light to improve the energy consumption of the liquid crystal display..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1113001 (2016)
Characteristics of All-optical Wavelength Conversion Based on Quantum-dot Semiconductor Optical Amplifier
GUAN Lei, WANG Zhuo-ran, YUAN Guo-hui, LIN Zhi-yuan, and YANG Meng
From the Optoelectronic Integrated Circuits (OEIC), according to the rate equations of carriers transition and the equations of optical field propagation in Quantum Dot Semiconductor Optical Amplifiers(QD-SOA), an equivalent circuit model of QD-SOA was established. Based on the circuit simulation method, the gain spectFrom the Optoelectronic Integrated Circuits (OEIC), according to the rate equations of carriers transition and the equations of optical field propagation in Quantum Dot Semiconductor Optical Amplifiers(QD-SOA), an equivalent circuit model of QD-SOA was established. Based on the circuit simulation method, the gain spectrum and saturated gain characteristics of QD-SOA were simulated and analyzed. The characteristics of wavelength conversions at the rates of 40 Gbps, 100 Gbps and 160 Gbps were studied based on the Cross Gain Modulation (XGM) of QD-SOA respectively. Meanwhile, the effect of signal light and probe light with different bias current and power on the properties of the output signal, including the extinction ratio and Q factor, was analyzed. The rate of wavelength conversions can reach 100 Gbps, Extinction Ratio(ER) is about 10 dB and Q factor is about 2.2. This study is quite important for improving the performances of wavelength conversion based on XGM of QD-SOA..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1113002 (2016)
Phenomenon of Multiple Fano Resonances Based on Coupled T-type Cavity
AN Hou-lin, ZHANG Guan-mao, HU Nan, SHI Yue, and WANG Zhi-shuang
Two Metal-Insulator-Metal (MIM) waveguide structures that consists of T-type cavity and baffle were proposed, and they are the positive T-type cavity structure and the inverted T-type cavity structure respectively. The transmission characteristics of this structure were calculated by using the Finite-Element Method(FEMTwo Metal-Insulator-Metal (MIM) waveguide structures that consists of T-type cavity and baffle were proposed, and they are the positive T-type cavity structure and the inverted T-type cavity structure respectively. The transmission characteristics of this structure were calculated by using the Finite-Element Method(FEM). The simulation results show the double Fano resonances for the positive T-type cavity structure, and the resonant wavelength can be easily tuned by changing the length and the height of the T-type cavity.The structure would be helpful for designing the nano-sensor with a sensitivity of 1620 nm/RIU and the figure of merit of 5.4×104.By inverting the T-type cavity, multiple Fano resonances are observed in the waveguide with a sensitivity of 1560 nm/RIU and the figure of merit of 9.37×104. The waveguide structure may have wide applications in highly integrated optical circuits , especially for nano-sensor and spectral splitter..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1113003 (2016)
High Peak Power Mid-infrared 2.8 μm Pulsed Fiber Laser
SHEN Yan-long, WANG Yi-shan, CHEN Hong-wei, HUANG Ke, TAO Meng-meng, LUAN Kun-peng, YU Li, YI Ai-ping, and FENG Guo-bin
A high peak power actively Q-switched mid-infrared fiber laser at 2.8 μm was demonstrated with a repetition rate of 1~10 kHz by employing a 975 nm laser-diode to pump a piece of heavily Er3+-doped ZBLAN double-clad fiber and a mechanical chopper into the cavity as the Q-switch. Stable Q-switched laser pulse with a maxiA high peak power actively Q-switched mid-infrared fiber laser at 2.8 μm was demonstrated with a repetition rate of 1~10 kHz by employing a 975 nm laser-diode to pump a piece of heavily Er3+-doped ZBLAN double-clad fiber and a mechanical chopper into the cavity as the Q-switch. Stable Q-switched laser pulse with a maximum pulse energy of 134.5 μJ, pulse duration of 127.3 ns and peak power of 1.1 kW was obtained at a repetition rate of 10 kHz under a proper pump power..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1114002 (2016)
Optical Self-guiding Diffuse Optical Tomography towards Near-infrared Functional Brain Imaging
ZHAO Hui-juan, QI Cai-xia, LIU Ming, QIN Zhuan-ping, ZHANG Yao, ZHANG Li-min, LI Jiao, ZHOU Zhong-xing, and GAO Feng
The image reconstruction of diffuse optical tomography (DOT) for near-infrared brain functional imaging is a severely ill-posed inverse problem. Different from the widely adopted multi-mode imaging method for providing anatomical-prior to DOT, this paper proposed an optical self-guiding scheme, called OT-DOT, and the cThe image reconstruction of diffuse optical tomography (DOT) for near-infrared brain functional imaging is a severely ill-posed inverse problem. Different from the widely adopted multi-mode imaging method for providing anatomical-prior to DOT, this paper proposed an optical self-guiding scheme, called OT-DOT, and the corresponding image reconstruciton algorithm is developed. The numerical and phantom validations are performed for the proposed method. Numerical reconstruction results indicate that quantitativeness ratio (QR) reconstructed with OT-DOT for the target is about 4.2 times bigger than that with traditional DOT for the known top layer thickness(TLT). QR from OT-DOT can be more 92% when the estimation error of TLT is less than ±10%. The noise-robustness testing indicates the reconstruction ability of OT-DOT and traditional DOT are roughly the same. Phantom experiments performed using a continuous-wave DOT system show that the reconstructed results with the proposed method is better than those with traditional DOT..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1117001 (2016)
Pressurization Actuation Based Variable Curvature Mirror Having Variable Thickness
ZHAO Hui, XIE Xiao-peng, XU Liang, DING Jiao-teng, LIU Mei-ying, and FAN Xue-wu
Based on the model of annular force based actuation, the reasons why it is hard for annular force based variable curvature mirror to obtain a large saggitus variation and maintain a high-accuracy surface figure simultaneously were analyzed. From the elasticity theory of thin plate, a physical model of variable curvaturBased on the model of annular force based actuation, the reasons why it is hard for annular force based variable curvature mirror to obtain a large saggitus variation and maintain a high-accuracy surface figure simultaneously were analyzed. From the elasticity theory of thin plate, a physical model of variable curvature mirror in which pressurization actuation and variable thickness design are combined together was proposed. The theoretical analysis results show that, by making the mirror thickness be variable from the center to the periphery portion and adopting the pressurization actuation, the large saggitus variation can be obtained while the surface figure accuracy can be maintained and higher than the annular line load variable curvature mirror. A duralumin prototype mirror was designed, fabricated and tested. The surface figure accuracy of the mirror before curvature variation is superior to λ/50 (632.8 nm). When a pressure of about 0.032 MPa is imposed, the mirror can provide a saggitus variation exceeding 22 μm and at the same the corresponding surface figure accuracy is still superior to λ/20 (632.8 nm), which verifies the theoretical analysis about variable thickness mirror and proves that the design combination integrating pressurization actuation and variable mirror thickness is a promising technical way to construct an applicable variable curvature mirror..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1122001 (2016)
Calculation of Field-dependent Aberrations of Fisheye Lens with the Transfer Equations of Field Ray
CAO Yi-qing, L Li-jun, and DENG Zhi-yong
Any a field ray, using its transfer equations, is traced reversely from the aperture stop of a fisheye lens to determine its initial position, i.e., the pupil spherical aberration. Then tracing the field ray in its forward direction, a relation curve between the field angle of object and image space can be obtained; a Any a field ray, using its transfer equations, is traced reversely from the aperture stop of a fisheye lens to determine its initial position, i.e., the pupil spherical aberration. Then tracing the field ray in its forward direction, a relation curve between the field angle of object and image space can be obtained; a polynomial expression is used to fit the relation curve. By the inversion operation to the polynomial expression, the distribution of object without distortion can be rectified from the distorted image to realize the purpose of eliminating the distortion of fisheye lens. Finally, we make numerical calculations of the pupil spherical aberration and image distortion to a 160°-fisheye lens, and rectify the distortion of object. The calculation results show that, the relative error of the pupil spherical aberration from the exact value is less than 1%, and the relative error of radial height of the rectified object distribution is less than 0.25%. The research shows that the method is feasible for the calculation of the field-dependent aberrations of fisheye lens..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1122002 (2016)
Orthogonal Optimization Design and Analysis of the LED Car Headlights
LIAO Xuan, GUO Zhen-ning, PAN Shi-fa, LI Jian-peng, and ZHANG Jia-ning
A type of LED automobile headlamp radiating structure was put forward, which was mainly composed of a ventilation pipe and a non-leaf fan. The corresponding model was generated in SolidWorks and the thermal condition was calculated with FloEFD thermal simulations. Results showed that the LED junction temperature was 14A type of LED automobile headlamp radiating structure was put forward, which was mainly composed of a ventilation pipe and a non-leaf fan. The corresponding model was generated in SolidWorks and the thermal condition was calculated with FloEFD thermal simulations. Results showed that the LED junction temperature was 148℃. Adopting two improved schemes, which rectangular fins and the honeycomb structure were filled into ventilation pipe respectively, the junction temperature of LED headlamps decreased to 102.01℃ and 86.20℃ respectively. With the orthogonal experiment, the scheme of filling honeycomb structure indicated that the factors affecting the system heat dissipation performance were as follows: the cellular equivalent diameter, honeycomb type, filling length, wall thickness and ventilation tube length. Therefore, the optimal heat dissipation structure was obtained by the parameter value of this order. Simulation results showed that, after orthogonal optimization, the temperature of LED headlamps was reduced to 75.17℃, which further improved the heat dissipation performance of the whole structure. Finally, the relationship between the wind speed and the thermal structure’s substrate temperature was discussed. The result demonstrated that when the wind speed was lower than 5m/s, the temperature decreased sharply with the increase of wind speed, and when the wind speed was higher than 5m/s, the temperature descend trend was relatively slow..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1122003 (2016)
Squeezing Propagation through Double Electromagnetically Induced Transparency in a Tripod-Type Atomic System
LI Yuan, XU Xue-yuan, ZHANG Wei, GAO Wei-qing, ZHANG Jun-xiang, and XU Jin-zhang
The squeezed probe light transmission characteristic through a double electromagnetically induced transparency in tripod-type atomic system was investigated by using the Heisenberg-Langevin approach. The results show that, the squeezing can survive in two electromagnetically induced transparency windows independently. The squeezed probe light transmission characteristic through a double electromagnetically induced transparency in tripod-type atomic system was investigated by using the Heisenberg-Langevin approach. The results show that, the squeezing can survive in two electromagnetically induced transparency windows independently. The output squeezing in tripod-type atoms can be better preserved when the frequency detunings of two coupled fields are equal. It is found that the output squeezing is also determined by the Rabi frequency of coupling fields, optical depth and dephasing rate of atoms, and detection frequency. This study has a potential application in multi-channel quantum memory for quantum network..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1127001 (2016)
Quantum Properties of the State via Operation of Superposition of Photon Subtraction n Times and Addition n Times on Chaotic Field
LU Dao-ming
Superposition of photon subtraction and addition n times excited chaotic field was constructed. Using numerical methods, the squeezing, antibunching effect and statistical property of the quantum state were analyzed. The influences of the average photon number of chaotic field, superposition coefficient of operators anSuperposition of photon subtraction and addition n times excited chaotic field was constructed. Using numerical methods, the squeezing, antibunching effect and statistical property of the quantum state were analyzed. The influences of the average photon number of chaotic field, superposition coefficient of operators and times of operators operation on its quantum properties were discussed. Numerical results show that the squeezing is not displayed, while the antibunching effect and sub-poissonian statistical property are displayed. Further, its antibunching effect and sub-poissonian statistical property are weakened with increase of average photon number of chaotic field. Its antibunching effect and sub-poissonian statistical property are strengthened as the ratio of photon operator addition in superposition operation increases. On the other hand, its sub-poissonian distribution property is strengthened with increase of times of operators operation..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1127002 (2016)
Dynamics of Quantum Coherence in a Fiber-coupled Two-cavity System
CAO De-wei, ZHANG Yi-xin, and HU Zheng-da
In order to explore the dynamics and distribution properties of quantum coherence in cavity quantum electro dynamics system, a system was built by connecting two cavities through an optical fiber, where an atomic ensemble could be trapped in each cavity. By employing the quantum relative entropy measure of quantum coheIn order to explore the dynamics and distribution properties of quantum coherence in cavity quantum electro dynamics system, a system was built by connecting two cavities through an optical fiber, where an atomic ensemble could be trapped in each cavity. By employing the quantum relative entropy measure of quantum coherence and introducing the concept of quantum coherence imbalance, the coherence dynamics of the system and the influence of the fiber-cavity coupling strength on the coherence distribution were studied. It is found that the global coherence of the atoms in the two cavities preserves well in the strong coupling limit by increasing the fiber-cavity coupling strength, and perfect transfer of atomic coherence from one cavity to the other cavity can be realized under specific configurations for the fiber-cavity coupling strength, the atom-cavity coupling strength and the atom number. Considering the presence of dissipations for the cavities, fibers and atoms, the evolutions of coherence under different dissipation rates with that in the non-dissipation case were compared. It is shown that the coherence of the coupled two-cavity system and the atomic coherence in each cavity are both reduced by dissipations..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1127003 (2016)
Design and Verification of Space Adaptability for Ratioing Radiometer
LI Meng-fan, ZOU Peng, SUN Zhen, JIN Jie, CAO Xing-jia, HUANG Wen-xin, HONG Jin, SI Xiao-long, and QIAO Yan-li
According to the environment during launch and on orbit, special design was carried out to improve spatial environment adaptability for ratioing radiometer which consists of integrating sphere, diffuser shutter and electronic optic cut. Weak part of ratioing radiometer was strengthened after making mechanical simulatioAccording to the environment during launch and on orbit, special design was carried out to improve spatial environment adaptability for ratioing radiometer which consists of integrating sphere, diffuser shutter and electronic optic cut. Weak part of ratioing radiometer was strengthened after making mechanical simulation. The temperature stability under thermal vacuum environment was realized by limiting the power of components and surface heat treatment. The radiation-proof ability was guaranteed by employing space-grade optical coating and making structure shield. Spatial environment adaptability was verified by mechanical, thermal vacuum and space radiation experiments. Mechanical testing results show that the fundamental frequency of the ratioing radiometer is about 540 Hz. The variation of the ratio for sun view to diffuser view of ratioing radiometer after mechanical experiments is within 0.31%. The structural strength and rigidity of the ratioing radiometer could meet the design requirement that the fundamental frequency should be above 100 Hz. The electronic components of the ratioing radiometer maintain normal during thermal vacuum experiments. The degradation of directional/hemisphere reflectance for the ratioing radiometer at 485 nm after space radiation tests is within 2%, while the change of directional/hemisphere reflectance in longer wavelength is negligible. The above results show that the ratioing radiometer has good space adaptability and is able to work steadily and reliably in complex space environment, which meets the needs for aerospace application requirements..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1128001 (2016)
Mode Properties and Sensing Technology of Silica Capillary Ellips-microbubble
LIU Bin-bin, ZHANG Meng, and WU Gen-zhu
Mode and refractive index sensing properties of silica capillary microbubble were studied numerically using a finite element method. Mode characteristics such as quality factor, effective refractive index and percentage of light intensities inside the core were determined for different bubble diameters and shell thicknMode and refractive index sensing properties of silica capillary microbubble were studied numerically using a finite element method. Mode characteristics such as quality factor, effective refractive index and percentage of light intensities inside the core were determined for different bubble diameters and shell thicknesses, and the potential application of microbubble in the high sensitivity and high resolution refractive index sensing was discussed. The results show that, optimized shell thicknesses sizes for the best sensitivity and resolution can be obtained, which is about 1 μm for microbubble with a diameter of 350 μm. Around this thickness, the resolution does not vary too much with bubble size, the sensitivity of the second order mode with a high quality-factor is higher than that of the first order mode. Therefore, in a practical sensing application, the second order mode is recommended since it can reduce the level of control needed on the shell thickness during device fabrication. It has a certain theoretical reference value to guide the experimental production process..
Acta Photonica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 45, Issue 11, 1128002 (2016)
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