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Effect of laser pulse shape and duration on spectrum width of coherent LIDAR

Chinese Optics Letters 2014年第A1期12卷 165-168页

作者：步志超陈思颖张寅超陈和葛宪莹郭磐 Beijing Institute of Technology Beijing 100081 China

Doppler spectrum width, which relates to wind turbulence, is one of the essential parameters of coherent LIDAR. Using the Fourier transform theorem and the definition of correlation function, the power spectrum function in the stationary condition is deduced. The effects of pulse shape, pulse duration and the windowing are included. The spectrum width resulted from the turbulence is given under Kolmogorov turbulence model. Based on the power spectrum theory, the spectrum broadening by different pulse shapes and pulse durations are calculated. To validate the accuracy of the theory and usage in the retrieval of turbulence parameters, the numerical simulations of the echo signal are carried out in turbulence conditions. The statistics characteristics of the spectrum broadening from laser pulse shapes and durations are inverted aud compared. The results show that the spectrum broadening varies greatly due to the selection of pulse shapes and pulse durations, and the numerical simulation is in accordance with the theory results.

关键词： 280.3640 Lidar 070.4790 Spectrum analysis 010.1330 Atmospheric turbulence 170.3340 Laser Doppler velocimetry

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Influence of dynamic parameters on interacting efficiency between ground-based laser and air-based flying target

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Chinese Optics Letters 2014年第A2期12卷 1-7页

作者：邓少永张世强孙艳宏关小伟 Northwest Institute of Nuclear Technology Xian710024 China

We simulate the integrated effects of atmospheric aberration, atmospheric turbulence, thermal blooming, random jitter of laser＇s intensity and phase, speed of wind, direction of wind, absorption of air, kinetic cooling of CO2 and N2, speed of target, output power and beam quality of laser, wavelength, focus length, and the launch altitude of laser to accurately simulate the transmission loss of the laser＇s energy, concentration of laser＇s power and other beam quality parameters of the laser propagating to the dynamic target. And we evaluate the efficiency of laser＇s irradiation on the target more accurately for the optical link of ground-toairspace. We also investigate influences of characteristics of dynamic parameters （Strehl＇s ratio, RMS of wavefront, spatial distribution of intensity on the target, the real focus on the optical link and the peak intensity along the propagation path） including speed of wind, direction of wind, speed of target and the kinetic cooling effect of air, especially. We conclude that the higher speed of wind and target weakens the thermal blooming of atmosphere and improves the beam quality and efficiency of laser＇s irradiation on the target. The kinetic cooling effect of air is more remarkable to improve the beam quality irradiating on the target at the initial part of the propagation path of the laser. The changed direction of wind weakens the atmospheric aberration and directs to better beam quality and higher efficiency of laser＇s irradiation on the target.

关键词： 010.1290 Atmospheric optics 010.1300 Atmospheric propagation 010.1330 Atmospheric turbulence

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Numerical simulation and analysis of dynamic compensation for atmosphere turbulence based on stochastic parallel gradient descent optimization

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Chinese Optics Letters 2012年第B6期10卷 5-8页

作者：马慧敏张鹏飞张京会乔春红范承玉 Key Lab of Atmospheric Composition and Optical Radiation Anhui Institute of Optics and Fine Mechanics Chinese Academy of Sciences Hefei 230031 China

We present the numerical simulation and analysis of the bandwidth estimation for adaptive optics （AO） systems based on stochastic parallel gradient descent （SPGD） optimization. Time-varying atmosphere turbulence due to wind velocity and turbulence structure constant is considered in the dynamic simulation. The performance of SPGD system with different iteration frequencies is studied in detail. A formula given that estimates the Strehl ratio degradation after SPGD adaptive control due to the increasing proportion of the number of deformable mirror actuator times Greenwood frequency to iteration frequency based on numerical analyses, can be used to roughly predict the required iteration frequency under the condition of various Greenwood freauencies.

关键词： 010.0010 Atmospheric and oceanic optics 010.1080 Active or adoptive optics 010.1330 Atmospheric turbulence

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Performance of free-space optical communication systems using circle polarization shift keying with spatial diversity receivers

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Chinese Optics Letters 2013年第14期11卷 1-4页

作者：刘超姚勇杨彦甫袁易君赵宇峰于本双 Department of Electronic and Information Engineering Shenzhen Graduate School Harbin Institute of Technology Shenzhen 518055 China

A closed-form bit-error rate （BER） expression is derived for free-space optical （FSO） communication systems with circle polarization shift keying and spatial diversity receivers in the gamma-gamma （GG） distribution fading channel. This model can predict the performance without the need of lengthy simulation runs. The performance can be analyzed by some system parameters such as atmospheric conditions, link length, communication wavelength, receiver aperture size, and number of spatial diversity receivers. Numerical results demonstrate the influence of the above parameters on the FSO systems and show quantitatively the differences in behavior among various different parameters.

关键词： 010.1300 Atmospheric propagation 010.1330 Atmospheric turbulence 060.2605 Free-space optical communication 060.4080 Modulation

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