Diffraction of laser radiation by a binary zone plate with fractional order

Abstract

Hybridly polarized beams have attracted increasing attention in recent years. Due to the features of spatial polarization and phase singularity, they can be used in STED microscopy, as optical tweezers, in nanoprocessing, to excite surface plasmon polaritons, in nonlinear optics, in quantum optics, and in telecommunication technologies. In this work, using the FDTD method, we simulated the passage of laser radiation through a binary spiral zone plate with a fractional order m=0.5 and a focal length of 0.532 μm. Quartz glass n=1.5 was assumed as the material for the relief of the zone plate. The zone plate radius was 4 μm. A TE polarized Gaussian beam with a wavelength of 0.532 μm was fed to the input. In this work, the intensity distribution and the Poynting vector in focus were studied. The possibility of forming an optical vortex with a fractional order was demonstrated.