Graphene-coupled silica microsphere polarizer

Abstract

Polarization-selective devices can control the polarization of the optical system. We develop a compact hybrid structure based on silica microsphere and monolayer graphene to tune the polarization of the optical system, which the working principle is polarization-dependent absorption of graphene combined with silica microsphere through whispering-gallery (WG) TE mode and TM mode. Because of different field distributions and polarization states of resonant modes in microsphere, the gap distance between microsphere and graphene can modify the quality factor and resonant wavelength of microsphere to realize the different variations for TE and TM WG modes, respectively. As gap distance is reduced from 2.2 µm to 0.3 µm, 11 dB polarization extinction ratio is realized between resonance polarized mode in the 90° polarization direction and that in the 0° polarization direction. Furthermore, for different original gap distance between microsphere and graphene, corresponding to different preconditions of quality factors of microsphere, one can obtain a polarization-selective device with the adjustable bandwidth. This results offer an attractive and effective photonic platform to achieve high-performance polarization-selective devices.