Chengyu Fan

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.

Influence of oceanic turbulence on propagation of a radial Gaussian beam array

The analytical expression for the root-mean-square (Rms) beam width of the radial Gaussian beam array propagating in oceanic turbulence is derived, where the coherent combination is considered. Meanwhile, the analytical expression for effect of the turbulence on the beam F is also obtained. Giving a comparison of results of F calculated by the analytical expression and the previously integrating one, it can be seen that the two results are in agreement with each other exactly. Further, the influences of the rate of dissipation of mean-squared temperatureχ(T), the rate of dissipation of kinetic energy per unit mass of seawater εand the ratio of temperature to salinity contribution to the refractive index spectrum w are investigated. The results indicate that the Rms beam width increases as χ(T) increases, εdecreases and the salinity-induced turbulence dominates. Moreover, the changings of effective radius of curvature with mentioned above parameters are studied. The strength of turbulence determines the value of effective radius of curvature, and which decreases asχ(T) and w increases, and εdecreases.

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.

Decoherence of orbital angular momentum tangled photons in non-Kolmogorov turbulence.

Orbital angular momentum (OAM) entangled photons propagating through non-Kolmogorov turbulence are studied by numerical simulations. Here, the paper uses the multiphase screen model, especially focusing on the influences of the azimuthal mode and the turbulence parameters (i.e., the generalized exponent, the outer scale of turbulence, and the inner scale of turbulence) on entanglement evolution in the weak scintillation regime. The results indicate that the azimuthal mode, the generalized exponent, and the outer scale of turbulence have obvious influences on OAM entanglement. However, the influence of the turbulence inner scale on OAM entanglement can be ignored.

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.