Pancharatnam–Berry Phase Induced Spin-Selective Transmission in Herringbone Dielectric Metamaterials

Abstract

A new means of achieving a strong chiral response through a spin-selective interference between light of different Pancharatnam-Berry (PB) phases inside a birefringent metamaterial grating was developed. The numerical simulations were carried out by using the commercially available Matlab and CST Microwave Studio (CST MWS) softwares. Matlab was used for plotting the frequency response of the analytically derived transmission coefficients. CST MWS was used to perform time-domain solver calculations of the herringbone device, where periodic boundary conditions were chosen for each unit cell in the x and y directions, while the z direction was set as open. Linearly polarized light was used and the corresponding x and y response amplitudes and phases were utilized to calculate the circularly polarized response. Impressively, the herringbone metasurface not only provides an experimental cross-polarization transmittance of 0.62 for red, but also has a greater transmittance than pure silicon alone or any other similar works carried out using planar metasurfaces to achieve a chiral response. Due to the lack of metallic structures, losses are negligible and the application of subwavelength gratings in conjunction with a geometric phase provides a robust and novel means of achieving such a functionality, which may provide a preferable route for optical computing or image processing where the demand on high efficiency is crucial.