Research On Wide-angle Oblique Incidence Metalens Based On Pancharatnam-berry Phase

Optical metasurface is an array on a two-dimensional plane in the micro nano field.It can regulate the wavefront,change the phase distribution of the wavefront,and realize the micro regulation of light wave in the sub wavelength range.To a great extent,the metasurface can realize the complex planar optical system designed by electron beam exposure and micro design.Therefore,with the development of micro nano processing,the metalens realized by metasurface has gradually entered people’s vision.This super surface process has great advantages over the phase change of traditional optics in function and preparation,and miniaturization and integration give more unique advantages,reducing the defects of large volume and high weight of traditional optical devices.In many practical applications,isotropic metalenses made of nano materials in the sub wavelength field have been widely used.However,the aberration caused by off-axis illumination is an important problem of single-layer optical metasurface in regulating the wave front of light.In this paper,a double-layer metasurface structure is proposed,which can realize a metalens with wide-angle incidence and eliminate aberration.The metalens can effectively realize wide-angle 80 degree aberration free focusing.Based on this idea,the single angle aberration free focusing and interval range angle aberration free focusing are designed,and the main design wavelength is 632.8nm.For single angle aberration free focusing and interval range angle aberration free focusing,continuous phase design and gradient discrete phase design are realized,which can effectively eliminate the influence of aberration.The metalens can be composed of two layers of silicon nitride nano column materials,two layers of nanocrystalline silicon nano column materials or two layers of monocrystalline silicon nano column materials according to certain arrangement rules and calculation rules.This paper mainly studies the wide-angle aberration free focusing based on changing the incident angle of the incident light.The theoretical calculation and simulation data show that after the left-handed circularly polarized incident light with different incident angles passes through the first layer of metasurface,the polarization state becomes right-handed circularly polarized light,and with the increase of geometric phase,then the right-handed circularly polarized light will be vertically incident into the silica transparent substrate,and then transmitted to the second layer of metasurface.The second layer of metasurface is a focused metasurface.The main function is to focus the RCP light from the substrate,turn it into LCP light after passing through the second layer of metasurface,and increase the required Pancharatnam-Berry phase to realize aberration free focusing at the required position.This scheme provides a broad idea for designing aberration free focusing in a wider angle range Other integrated metalenses have great application prospects.