Jinghui Zhang

Average intensity of M × N Gaussian array beams in oceanic turbulence.

Based on the power spectrum of oceanic turbulence proposed by Nikishov, the analytical expressions for average intensity of M×N Gaussian array beams propagating in oceanic turbulence are derived, where the coherent and incoherent combinations are considered. Using the focused beam, the intensity can be received at the same point. The changes of the average intensity versus three oceanic parameters are investigated.

Two-wavelength ghost imaging through atmospheric turbulence

Recent work has indicated that ghost imaging might find useful application in standoff sensing where atmospheric turbulence is a serious problem. There has been theoretical study of ghost imaging in the presence of turbulence. However, most work has addressed signal-wavelength ghost imaging. Two-wavelength ghost imaging through atmospheric turbulence is theoretically studied in this paper. Based on the extended Huygens-Fresnel integral, the analytical expressions describing atmospheric turbulence effects on the point spread function (PSF) and field of view (FOV) are derived. The computational case is also reported.

Adaptive optical ghost imaging through atmospheric turbulence

We demonstrate for the first time (to our knowledge) that a high-quality image can still be obtained in atmospheric turbulence by applying adaptive optical ghost imaging (AOGI) system even when conventional ghost imaging system fails to produce an image. The performance of AOGI under different strength of atmospheric turbulence is investigated by simulation. The influence of adaptive optics system with different numbers of adaptive mirror elements on obtained image quality is also studied.

Light filaments with higher-order Kerr effect

The influence mechanism of higher-order Kerr effect on the propagation of laser beam is investigated by a modified model, which indicates that a collapsing wave will transform into a universe blowup profile. The analysis of higher-order terms of the nonlinear refractive index shows that the filamentation process can be induced by Kerr self-focusing without the occurrence of the ionization effect. The determining role of the combination of self-focusing and spontaneous defocusing and the energy reservoir in formation of lengthy filament is confirmed visually.

Phase structure function and AOA fluctuations of plane and spherical waves propagating through oceanic turbulence

Based on the characteristics of a hypergeometric function, the analytical expressions for the phase structure function and angle-of-arrival (AOA) fluctuations of plane and spherical waves propagating through oceanic turbulence are derived. The results are verified by comparing them with the numerical calculations of the definitions using four important parameters (i.e., the rate of dissipation of mean-squared temperature the rate of dissipation of kinetic energy per unit mass of fluid the ratio of temperature to salinity contribution to the refractive index spectrum and the Kolmogorov microscale The relation between AOA fluctuations and the spatial coherence radius is also investigated.

Effect of atmospheric turbulence on entangled orbital angular momentum three-qubit state

The entangled orbital angular momentum (OAM) three photons propagating in Kolmogorov weak turbulence are investigated. Here, the single phase screen model is used to study the entanglement evolution of OAM photons. The results indicate that the entangled OAM three-qubit state with higher OAM modes will be more robust against turbulence. Furthermore, it is found that the entangled OAM three-qubit state has a higher overall transmission for small OAM values.

Quantum polarization fluctuations of partially coherent dark hollow beams in non-Kolmogorov turbulence atmosphere*

Non-classical polarization properties of dark hollow beams propagating through non-Kolmogorov turbulence are studied. The analytic equation for the polarization degree of the quantization partially coherent dark hollow beams is obtained. It is found that the polarization fluctuations of the quantization partially coherent dark hollow beams are dependent on the turbulence factors and beam parameters with the detection photon numbers. Furthermore, an investigation of the changes in the on-axis propagation point and off-axis propagation point shows that the polarization degree of the quantization partially coherent dark hollow beams presents oscillation for a short propagation distance and gradually returns to zero for a sufficiently long distance.

Influence of the platform jitter on intensity fluctuation for laser launch system

The jitter of the transmitting system can cause the light intensity fluctuation at the target position of the laser transmission, which affects the performance of the laser communication, imaging and the adaptive optical system. In this paper, the platform jitter is modeled by Gaussian random fluctuation phase and the analytic expression of the system jitter effect on the fluctuation of light intensity is obtained under the vacuum condition based on extended Huygens-Fresnel principle. The numerical simulation is compared with the theoretical expression and the consistency is obtained. At the same time, the influence of the jitter of the launch system on the intensity fluctuation of the target system under different turbulence conditions is analyzed by numerical simulation. The result show that normalized intensity fluctuation variance induced by platform jitter seems to be unrestricted. The jitter of the transmitting system has a more important influence on the fluctuation of the target position caused by the atmospheric turbulence, as the jitter increase. This result provides a reference for the application of the actual laser transmission system.

Research on temperature characteristics of laser energy meter absorber irradiated by ms magnitude long pulse laser

The research on temperature characteristics for large-energy laser energy meter absorber is about continuous wave (CW) laser before. For the measuring requirements of millisecond magnitude long pulse laser energy, the temperature characteristics for absorber are numerically calculated and analyzed. In calculation, the temperature field distributions are described by heat conduction equations, and the metal cylinder cavity is used for absorber model. The results show that, the temperature of absorber inwall appears periodic oscillation with pulse structure, the oscillation period and amplitude respectively relate to the pulse repetition frequency and single pulse energy. With the wall deep increasing, the oscillation amplitude decreases rapidly. The temperature of absorber outerwall is without periodism, and rises gradually with time. The factors to affect the temperature rise of absorber are single pulse energy, pulse width and repetition frequency. When the laser irradiation stops, the temperature between absorber inwall and outerwall will reach agreement rapidly. After special technology processing to enhance the capacity of resisting laser damage for absorber inwall, the ms magnitude long pulse laser energy can be obtained with the method of measuring the temperature of absorber outerwall. Meanwhile, by optimization design of absorber structure, when the repetition frequency of ms magnitude pulse laser is less than 10Hz, the energy of every pulse for low repetition frequency pulse sequence can be measured. The work offers valuable references for the design of ms magnitude large-energy pulse laser energy meter.

Tip-tilt adaptive correction based on stochastic parallel gradient descent optimization algorithm

Adaptive optics correcting technique based on stochastic parallel gradient descent (SPGD) control algorithm is an alternative approach which is independent of wavefront sensor and optimizes the performance metric directly. In this paper we establish a simulation model of tip-tilt adaptive optics system, where SPGD optimization algorithm is used to correct the tip-tilt aberration induced by dynamic turbulence. The distance between the measured centroid of a blurring image and the demarcated centroid of the ideal image is considered as the system performance metric, and signals applied to compensation of the drifting atmosphere are generated for tip-tilt mirror. The sensitivity of the performance metrics is investigated, and the convergence rate and the stability are analyzed. By means of this optimization algorithm, the centroid of the image is modified in real time, which results in the improvement of the long exposure image.