Highly customized and miniaturized structured light is expected in many application fields.A kind of structured vortex generators is proposed based on a metasurface consisting of rectangular nanoholes etched in a silver film,and the generated vortices with the same or different topological charges are distributed along the radial direction.The geometric metasurface is completed with the help of optical holography technology,and the structured vortex generator possesses high working efficiency and large information capacity.The proposed vortex generators work under circularly polarized light illumination,and the reproduced vortices of multiplexing vortex generator depend on the handedness of the circularly polarized light.This work paves a way to generate new structured light fields.The radially distributed vortices may be utilized to simultaneously screen or separate microparticles.The compact design of the structured vortex generator and the convenient switch of different structured vortices will be a benefit to expand the applications of structured vortex fields.
ZHEN MOUCHANGDA ZHOUPEIYAO LUQINGYANG YUESHUYUN WANGSHUYUN TENG
Using the interference of speckle and the spherical reference wave, we extract the real and the imaginary parts of the complex amplitudes of the speckle in large angle scattering. By calculating the spatial correlation functions of intensity, we find that the speckle has a property of regional fractality, i.e. the fractal exponent equals 1 in a small spatial region and it becomes less than 1 in a bigger region. The empirical analytic expression of the intensity correlation function is gained. The probability density distributions of the intensities and the complex amplitudes show that the regional fractal speckle still obeys zero-mean circular complex Gaussian statistics.
Transmission of an anisotropic metasurface is analyzed in a polar base relying on the Jones calculus, and polarization conversion from the spatial uniform polarization to the spatial nonuniform polarization is explored.Simple and compact polarization converters based on rectangular holes or cross holes etched in silver film are designed, and polarization conversions from the linear and circular polarization to the radial and azimuthal polarization are realized. Numerical simulations of three designed polarization converters consisting of rectangular holes equivalent to polarizers and quarter-and half-wave plates, exhibit the perfect polarization conversion.The experiment results consistent with the simulations verify theoretic predictions. This study is helpful for designing metasurface polarization converters and expanding the application of a metasurface in polarization manipulations.
We report the experimental method of angle-resolved in-plane light scattering for random surface parameter extraction.In the measurement of the scattered intensity profile at a certain angle of incidence,the perpendicular component of wave vector remains constant,which is realized by controlling the movement of the detector along a specified circular arc segment.We use the central S-peak and the half-width of the diffused intensity profiles and their variations to obtain the roughness w,the lateral correlation lengthξand roughness exponent a of the rough surface sample.The measurement copes strictly with the theoretical analysis,and the inherent problem in previous in-plane light scattering experiment is overcome so that the changes of the perpendicular component of wave vector affect the half width a diffused intensity profile and the measurement accuracy.
LI Hai-XiaLIU Chun-XiangCHEN Xiao-YiZHANG Mei-NaCHENG Chuan-Fu
A practicable experimental method for measuring scattering on rough surfaces is reported. The scattered patterns are captured on a screen composed of two pieces of ground glass and then imaged using a charge- coupled device. The scattered intensity profiles are extracted by converting the patterns in real space into the wave vector space. Isotropic and anisotropic samples of the rough backsides of silicon wafer are investigated respectively, and their intensity profiles are measured. The profiles of the anisotropic sample are obtained by reading the pixels on the specific orientation curves. The parameters of the samples are extracted using angle-resolved light-scattering schemes and theories. The results well agree with measurements obtained using an atomic force microscope.
