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Non-Gaussian statistics of partially coherent light in atmospheric turbulence

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Chinese Physics B 2020年第6期29卷 54-59页

作者： Hao Ni Chunhao Liang Fei Wang Yahong Chen Sergey APonomarenko Yangjian Cai School of Physical Science and Technology&Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow UniversitySuzhou 215006China Shandong Provincial Engineering and Technical Center of Light Manipulation&Shandong Provincial Key Laboratory of Optics and Photonic Device School of Physics and ElectronicsShandong Normal UniversityJinan 250014China Department of Electrical and Computer Engineering Dalhousie UniversityHalifaxNova ScotiaB3J 2X4Canada Department of Physics and atmospheric Science Dalhousie UniversityHalifaxNova ScotiaB3H 4R2Canada

We derive theoretically and verify experimentally a concise general expression for the normalized intensity correlations(IC)of partially coherent light in a weak atmospheric turbulence in the fast detector measurement *** derived relation reveals that the medium turbulence acts,in general,as an additional noise source enhancing the IC of partially coherent *** maximum of the beam IC is,in general,enhanced,causing the fields to exhibit super-Gaussian *** the other hand,the relation indicates that turbulence-induced noise is negligible for sufficiently low coherence light,which reveals the condition for the turbulence-free correlation imaging.

关键词： partially coherent beam atmospheric turbulence intensity correlation

Partially coherent Gaussian–Schell model pulse beam propagation in slant atmospheric turbulence

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Chinese Physics B 2014年第6期23卷 295-303页

作者：李亚清吴振森张元元王明军 School of Physics and Optoelectronic Engineering Xidian University School of Physics and Electronic Engineering Xianyang Normal College

Based on the extended Huygens-Fresnel principle, a two-frequency, two-point cross-spectral density function of partially coherent Gaussian-Schell model pulse （GSMP） beam propagation in slant atmospheric turbulence is derived. Using the Markov approximation method and on the assumption that （w1 - w2）/（w1 ＋ w2） ≤ 1, the theory obtained is valid for turbulence of any strength and can be applied to narrow-band signals. The expressions for average beam intensity, the beam size, and the two-frequency complex degree of coherence of a GSMP beam are obtained. The numerical results are presented, and the effects of the frequency, initial pulse width, initial beam radius, zenith angle, and outer scales on the complex degree of coherence are discussed. This study provides a better understanding of the second-order statistics of a GSMP beam propagating through atmospheric turbulence in the space-frequency domain.

关键词： atmospheric propagation partial coherence atmospheric turbulence

Propagation of the off-axis superposition of partially coherent beams through atmospheric turbulence

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Chinese Physics B 2009年第2期18卷 571-580页

作者：张恩涛季小玲吕百达 Institute of Laser Physics and Chemistry Sichuan University School of Sciences of Southwest Petroleum University College of Electronic Engineering Sichuan Normal University

The propagation properties of the off-axis superposition of partially coherent beams through atmospheric turbulence and their beam quality in terms of the mean-squared beam width w（z） and the power in the bucket （PIB） are studied in detail, where the effects of partial coherence, off-axis beam superposition and atmospheric turbulence are considered. The analytical expressions for the intensity, the beam width and the PIB are derived, and illustrative examples are given numerically. It is shown that the maximum intensity/max and the PIB decrease and w（z） increases as the refraction index structure constant Cn^2 increases. Therefore, the turbulence results in a degradation of the beam quality. However, the resulting partially coherent beam with a smaller value of spatial correlation parameter γ and larger values of separate distance Xd and beam number M is less affected by the turbulence than that with a larger value of y and smaller values of Xd and M. The main results obtained in this paper are explained physically.

关键词： off-axis superposition of partially coherent beams atmospheric turbulence propagation property beam quality

Scintillation of partially coherent Gaussian–Schell model beam propagation in slant atmospheric turbulence considering inner- and outer-scale effects

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Chinese Physics B 2014年第7期23卷 409-416页

作者：李亚清吴振森张元元王明军 School of Physics and Optoelectronic Engineering Xidian University School of Physics and Electronic Engineering Xianyang Normal College

Based on the modified Rytov theory and the international telecommunication union-radio （ITU-R） slant atmospheric structure constant model, the uniform scintillation index of partially coherent Gaussian-Schell model （GSM） beam propa- gation in the slant path is derived from weak- to strong-turbulence regions considering inner- and outer-scale effects. The effects of wavelength of beams and inner- and outer-scale of turbulence on scintillation are analyzed numerically. Compar- ison between the scintillation of GSM beams under the von Karman spectrum and that of beams under the modified Hill spectrum is made. The results obtained show that the scintillation index obtained under the von Karman spectrum is smaller than that under the modified Hill spectrum. This study can find theory bases for the experiments of the partially coherent GSM beam propagation through atmospheric turbulence.

关键词： atmospheric turbulence partially coherent beam scintillation atmospheric propagation

Far-field sonic boom prediction considering atmospheric turbulence effects: An improved approach

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Chinese Journal of Aeronautics 2022年第9期35卷 208-225页

作者： Jianling QIAO Zhonghua HAN Liwen ZHANG Wenping SONG Bifeng SONG Institute of Aerodynamic and Multidisciplinary Design Optimization School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710071China National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of AeronauticsNorthwestern Polytechnical UniversityXi'an710071China

Accurate prediction of sonic boom is one of key challenges for the design of a low-boom supersonic aircraft. For most of available far-field prediction methods, the effect of atmospheric turbulence appearing in the planetary boundary layer cannot be considered, which results in remarkable inaccuracy of predicting ground-level sonic boom waveform. Although some efforts have been made to overcome the shortcoming, the turbulence effects are not yet well described so far. This article proposes an improved method by extending the two-dimensional Heterogeneous One-Way Approximation for the Resolution of Diffraction(HOWARD) equation to account for the axial and transverse convections of wind fluctuation as well as the effect of temperature fluctuation. The proposed method is validated by comparing the predictions with the flight-test data of JAXA D-SEND#1 LBM, which shows that the result of the proposed method is in better agreement with the flight-test data than that of the method without considering atmospheric turbulence ***, distortion mechanism of sonic boom waveforms caused by atmospheric turbulence is analyzed by using the proposed method. It is indicated that the effect of turbulent convection makes uniform sonic-boom wavefronts irregular, which creates the condition of diffraction effect to perturb waveforms. Finally, the proposed method is applied to investigate the behavior of two types of waveforms given by the sonic boom minimization theory. Results show that a far-field waveform with a weaker initial shock is more beneficial for low-boom design of a supersonic aircraft.

关键词： atmospheric turbulence Augmented Burgers equation HOWARD equation Sonic boom Supersonic transport

Orbital angular momentum multiplexing communication system over atmospheric turbulence with K-best detection

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Science China(Information Sciences) 2021年第9期64卷 175-186页

作者： Yingmeng GE Liang WU Chuan ZHANG Zaichen ZHANG Laboratory of Efficient Architectures for Digital-communication and Signal-processing (LEADS) Southeast University National Mobile Communications Research Laboratory Southeast University Purple Mountain Laboratories

As the optical communication technology advances, vortex beam with orbital angular momentum(OAM) has gained wide attention due to its potential to significantly increase the channel capacity. Under the influence of atmospheric turbulence, there are still challenging problems in the OAM multiplexing system. To the best of our knowledge, in this paper one multiple-input-multiple-output(MIMO) detection technology named K-best detection, is first applied to the OAM multiplexing system. Numerical simulation results indicate the proposed solution enhances the performance of the optical communication system compared with data-aided least mean square(DA-LMS) and minimum mean squared error(MMSE) detection. Furthermore,with MMSE sorted QR decomposition(MMSE-SQRD) preprocessing, the performance of K-best detection can be further improved. When Cn~2= 1×10.14, about 4.4 dB signal-to-noise ratio(SNR) gain can be obtained by preprocessing at k = 2 while the complexity is not significantly increased. Computational complexity is also analyzed in this paper, results show that K-best detection with winner path extension(WPE) algorithm can achieve 43% system complexity reduction, achieving a compromise between performance and complexity in K-best detection.

关键词： orbital angular momentum atmospheric turbulence K-best detection MMSE-SQRD preprocessing WPE algorithm

Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path

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Chinese Physics B 2010年第9期19卷 647-654页

作者：李晋红张洪润吕百达 Institute of Laser Physics and Chemistry Sichuan University Department of Applied Physics Sichuan University

This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model （GSM） beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope ｜p｜ and the smaller the off-axis distance ｜d｜ are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The CSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.

关键词： partially coherent beams with edge dislocation atmospheric turbulence slant path

Generation and Application of Spatial atmospheric turbulence Field in Flight Simulation

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Chinese Journal of Aeronautics 2009年第1期22卷 9-17页

作者：高振兴顾宏斌南京航空航天大学民航学院

This article deals with generation and application of three-dimensional (3D) atmospheric turbulence field in large aircraft real-time flight simulation. The modeling requirements for the turbulence field of large aircraft flight simulation are analyzed here. The spatial turbulence field is generated in the frequency domain by using the Monte Carlo method,and then transformed back to the time domain with the 3D inverse Fourier transform. The von Karman model is adopted for an accurate description of the turb...

关键词： flight simulation atmospheric turbulence Monte Carlo method 3D Fourier transform wind gradients extension of turbulence field

Experimental Study on Influence of atmospheric turbulence on Coherence of Dual-Frequency Laser

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Chinese Physics Letters 2010年第8期27卷 88-91页

作者：王升杨苏辉吴霞赵长明朱启海 Department of Optoelectronics Beijing Institute of Technology Beijing 100081

The influence of atmospheric turbulence on the coherence of a dual-frequency laser beam is studied experimentally. An atmospheric turbulence simulator is inserted in one arm of a Mach-Zehnder interferometer. A single frequency laser beam and a dual-frequency laser beam with a frequency difference of 100 MHz travel through the interferometer, respectively. The visibilities of the interference fringes of the single and dual-frequency laser beams under different turbulent forces are compared. When the turbulence becomes stronger, the visibilities of the interference pattern of the single frequency interferometer decrease more rapidly. This shows that the atmospheric turbulence has less influence on the coherence of the dual-frequency laser beam. The linewidths broadened by the turbulence are calculated with the Wiener-Khintchine theory.

关键词： atmospheric turbulence Interference patterns Visibility Lasers