Aerosol extinction coefficient profile is an essential parameter for atmospheric radiation model. But it is difficult to get the full aerosol extinction profile from the ground to the tropopause especially in near ground precisely using backscattering lidar. A combined measurement of side-scattering, backscattering and Raman-scattering lidar is proposed to retrieve the aerosol extinction coefficient profile from the surface to the tropopause which covered a dynamic range of 5 orders. The side-scattering technique solves the dead zone and the overlap problem caused by the traditional lidar in the near range. Using the Raman-scattering the aerosol lidar ratio (extinction to backscatter ratio) can be obtained. The cases studies in this paper show the proposed method is reasonable and feasible.
Multiple-slit diffraction properties of high-polarization-order cylindrical vector (HCV) beams were studied in detail. Flowerlike intensity distributions are obtained after HCV beams passing through a linear polarizer. The intensity distributions of single-slit, double-slit, triple-slit and four-slit diffraction of high-order radially polarized (HRP) beams and high-order azimuthally polarized (HAP) beams are obtained, and analyzed with different slit spacings. It was indicated that diffraction fringes of HCV beams were not continuous. Faultage appeared, and the faultage number was 2P+1, which was only related to the polarization order number P, but independent of slit number N. It was found that the obvious and clear diffraction phenomenon would be obtained in the conditions 2ω≈ (N+1)D, N≥2 in which ω<sub>0</sub> is the beam waist radius and D is the slit spacing. This study can be used to detect and analyze higher-order vector beams. Besides, it helps to design special diffractive optical elements.
Vortex beams with integral and fractional topological charges are generated by an experimental setup with one phase-only liquid crystal spatial light modulator which efficiently modulates the phase retardation distributions of input beam. The intensity distributions and double-slit interference of vortex beams with integral and fractional topological charges are investigated in detail. Tilt appears in double-slit interference fringes of vortex beams. The fringe tilt amounts in the intermediate region are proportional to the topological charge l of vortex beams. The double-slit interference method can be utilized to determine the topological charge of vortex beams.