Yongping Huang

Evolution behavior of Gaussian Schell-model vortex beams propagating through oceanic turbulence

The analytical expressions for the cross-spectral density and average intensity of Gaussian Schell-model (GSM) vortex beams propagating through oceanic turbulence are obtained by using the extended Huygens-Fresnel principle and the spatial power spectrum of the refractive index of ocean water. The evolution behavior of GSM vortex beams through oceanic turbulence is studied in detail by numerical simulation. It is shown that the evolution behavior of coherent vortices and average intensity depends on the oceanic turbulence including the rate of dissipation of turbulent kinetic energy per unit mass of fluid, rate of dissipation of mean-square temperature, relative strength of temperature salinity fluctuations, and beam parameters including the spatial correlation length and topological charge of the beams, as well as the propagation distance.

Spreading and M 2-factor of elegant Hermite–Gaussian beams through non-Kolmogorov turbulence

Using a non-Kolmogorov power spectrum, analytical expressions for the beam width, angular spread and M 2-factor of elegant Hermite–Gaussian (EHG) beams through non-Kolmogorov turbulence are derived. It is shown that the beam-width spreading, angular spread and M 2-factor of EHG beams through non-Kolmogorov turbulence depend on the non-Kolmogorov turbulence, i.e. on the generalised exponent parameter, , the inner scale, l 0, and the outer scale, L 0, at a sufficient propagation distance. They increase with increasing outer scale for 3.6< <4, and with decreasing inner scale. Only at a shorter propagation distance is the effect of turbulence on the beam-width spreading and M 2-factor negligible. The results are interpreted physically.

Propagation properties based on second-order moments for correlated combination partially coherent Hermite–Gaussian linear array beams in non-Kolmogorov turbulence

Based on the extended Huygens–Fresnel principle, the definition of second-order moments of the Wigner distribution function (WDF), and the non-Kolmogorov turbulence spectrum, analytical expressions for the M 2-factor and Rayleigh range of correlated combination partially coherent Hermite–Gaussian linear array (PCHGLA) beams propagating through non-Kolmogorov turbulence have been derived. The effect of non-Kolmogorov turbulence and array beam parameters on the M 2-factor and Rayleigh range is discussed in detail. The results show that the M 2-factor and Rayleigh range, as well as their corresponding relative quantities of the PCHGLA beams, vary non-monotonically with increasing generalized exponent parameter α of the turbulence, and M 2-factor exists a maximum whereas Rayleigh range exists a minimum at α = 3.11, respectively. The M 2-factor and Rayleigh range of PCHGLA beams increase with increasing beam number but oscillate with increasing relative beam separation distance for < 1 and then increase monotonically as increases for > 1. The PCHGLA beams are less affected than the GSM linear array beam under the same conditions.

Propagation properties of partially coherent electromagnetic hyperbolic-sine-Gaussian vortex beams through non-Kolmogorov turbulence

Propagation properties of partially coherent electromagnetic hyperbolic-sine-Gaussian (PCESHG) vortex beams through non-Kolmogorov atmospheric turbulence, including the spectral degree of polarization and evolution behavior of coherent vortices and average intensity are investigated in detail by using the extended Huygens-Fresnel principle and the spatial power spectrum of the refractive index of non-Kolmogorov turbulence. It is shown that the motion, creation and annihilation of the coherent vortices of PCESHG vortex beams in non-Kolmogorov turbulence may appear with the increasing propagation distance, and the distance for the conservation of the topological charge depends on the turbulence parameters and beam parameters. In additions, the evolution behavior of coherent vortices, average intensity and spectral degree of polarization vary significantly for different values of the generalized exponent parameter and the generalized refractive-index structure parameter of non-Kolmogorov turbulence, and the beam parameters as well as the propagation distance.

Beam wander of partially coherent array beams through non-Kolmogorov turbulence

Based on the theory of second moments and non-Kolmogorov spectrum, the beam wander theory is extend to non-Kolmogorov turbulence, the general analytical expression of beam wander in non-Kolmogorov turbulence is derived. Beam wander depends on the non-Kolmogorov turbulence parameters and the initial second moments of the laser beam at the input plane. Taking the Gaussian Schell model array beams as an example, the effects of the generalized exponent parameter, inner scale, and outer scale of non-Kolmogorov turbulence and the beam separation distance, beam number, and coherence degree on the beam wander are studied in detail. It has been shown that the beam wander varies non-monotonically with increasing generalized exponent parameter of the turbulence. Furthermore, it increases as the inner scale decreases or outer scale increases, and decreases as the beam separation distance and beam number increase and the coherence of the beam becomes weaker. Our results also indicate that the beam wander could be reduced by adjusting the beam parameters appropriately.

A comparative study of standard and elegant Hermite–Gaussian beams propagating through turbulent atmosphere

Based on the extended Huygens–Fresnel principle and the definition of the second-order moments of the Wigner distribution function (WDF), the analytical expressions for the root-mean-square (rms) beam width and far-field divergence angle, curvature radius and M 2-factor of standard Hermite–Gaussian (SHG) and elegant Hermite–Gaussian (EHG) beams passing through turbulent atmosphere are derived and compared. It is shown that in turbulent atmosphere the far-field divergence angle of SHG and EHG beams is equal under the same conditions, but the rms beam width, curvature radius and the M 2-factor of SHG and EHG beams are different except for beam orders m = 0 and m = 1. The relative rms beam width, relative curvature radius and relative M 2-factor of SHG beams are less than those of EHG beams. Therefore, the conclusion that SHG beams are less influenced by turbulence than EHG beams can be drawn if we examine one of the above three relative beam parameters.

Effective radius of curvature of partially coherent Hermite–Gaussian beams propagating through non-Kolmogorov turbulence

Based on the extended Huygens–Fresnel principle and non-Kolmogorov spectrum, the analytical expression for the effective radius of curvature of partially coherent Hermite–Gaussian (PCHG) beams propagating through non-Kolmogorov turbulence is derived, and the relative effective radius of curvature is used to describe the effect of turbulence on the effective radius of curvature. It is shown that the effective radius of curvature of PCHG beams depends on the beam and non-Kolmogorov turbulence parameters and on the propagation distance. The variation of relative effective radius of curvature with increasing generalized exponent parameter α of non-Kolmogorov turbulence is non-monotonic. The longer the propagation distance is, the larger the effect of turbulence on the effective radius of curvature of PCHG beams is. The effective radius of curvature of PCHG beams with shorter wavelength, smaller beam order, larger beam waist width or better spatial coherence is more affected by the non-Kolmogorov turbulence. The results are interpreted physically.