Huiyun Wu

Study on power coupling of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere

As a new attractive application of the vortex beams, power coupling of annular vortex beam propagating through a two- Cassegrain-telescope optical system in turbulent atmosphere has been investigated. A typical model of annular vortex beam propagating through a two-Cassegrain-telescope optical system is established, the general analytical expression of vortex beams with limited apertures and the analytical formulas for the average intensity distribution at the receiver plane are derived. Under the H-V 5/7 turbulence model, the average intensity distribution at the receiver plane and power coupling efficiency of the optical system are numerically calculated, and the influences of the optical topological charge, the laser wavelength, the propagation path and the receiver apertures on the power coupling efficiency are analyzed. These studies reveal that the average intensity distribution at the receiver plane presents a central dark hollow profile, which is suitable for power coupling by the Cassegrain telescope receiver. In the optical system with optimized parameters, power coupling efficiency can keep in high values with the increase of the propagation distance. Under the atmospheric turbulent conditions, great advantages of vortex beam in power coupling of the two-Cassegrain-telescope optical system are shown in comparison with beam without vortex.

Beam shaping for uplink transmission of a relay mirror system

We establish the model of a two-Cassegrain-telescope system that is commonly used in a relay mirror system. With this model, uplink transmission of the relay mirror system is theoretically analyzed. We determined that uplink transmission with turbulence completely corrected is not an optimal mode. We improve power coupling efficiency of the two-Cassegrain-telescope system by optimizing the optical phase at the launching telescope by use of the stochastic parallel gradient descent algorithm. For a 10 km vertical uplink transmission, power coupling efficiencies of the system are 63.10%, 87.82%, and 97.80% corresponding to an open-loop mode, a closed-loop mode, and a closed-loop with optimization mode, respectively. For a 30 km vertical uplink transmission, power coupling efficiencies of the system are 22.35%, 82.66%, and 91.91%, corresponding to an open-loop mode, a closed-loop mode, and a closed-loop with optimization mode, respectively. The results show that power coupling efficiency of the two-Cassegrain-telescope system is significantly improved.

Properties of the flattened-vortex beam with aperture propagating through the turbulent atmosphere in a slant path

Abstract. A typical model of the flattened-vortex beam propagating through the turbulent atmosphere in a slant path is established, and the analytical formulas of the average intensity distribution at the observation plane are derived based on the extended Huygens-Fresnel principle. Under the H-V 5/7 turbulence model, the characteristics of the average intensity distribution at the observation plane are investigated, and the influences of the optical topological charge, the propagation distance, and the zenith angle of the propagation path are numerically analyzed.

Study on the SERS substrate composed of Au@Ag core-shell nanoparticles linked to SiO2 spheres

ABSTRACT We have developed a sensitive surface-enhanced Raman scattering (SERS) substrate composed of 60-nm Au@Ag core-shell nanoparticles linked to 360-nm SiO2 sphere base, which experimentally demonstrated that the detection limits for p-aminothiophenol (PATP), Rhodamine 6G (R6G) and 5,5-dithiobis(2-dinitrobenzoic acid) (DTNB) could be 10−13, 10−13 and 10−12 M, respectively. The fabrication method of the SERS substrate and the experimental investigation on the enhancement performance of the substrate are presented in detail in this article. The results show that the 360 nm SiO2-60 nm Au@Ag nanocomposites could be used as an excellent substrate for SERS detection of small organic molecules.

Study on the annular vortex beams with limited apertures and their propagation characteristics in the turbulent atmosphere

Considerable interest has been exhibited in characteristics of vortex beams due to their importance in basic science and some attractive applications. The general expression of vortex beams with limited aperture is developed, and the analytical formulas for the average intensity distribution of annular vortex beam with limited aperture in the turbulent atmosphere are derived based on the extended Huygens-Fresnel principle. Under the H-V 5/7 turbulence model, the characteristics of the annular vortex beams with limited apertures propagation through the turbulent atmosphere in a slant path are analyzed in the present paper.

Simulation of the solid state laser relay mirror system

The laser relay mirror technique has been under extensive research in recent years. The concept and the working process of the relay mirror system are analyzed in this paper. The model of the relay mirror system is established, the effect on 1km-altitude target with 500 m/s flying speed of the relay mirror system and the conventional ground-based laser system are calculated respectively. Obtains that the maximum coverage range of the ground-based laser system is 2.0 km and the maximum coverage range of the relay mirror system is 23.2 km. The relay mirror can largely open up the coverage range of the laser system and strengthen the attacking ability of the ground-based laser.