Modulation and enhancement of photonic spin Hall effect with graphene in broadband regions*

Abstract

The photonic spin Hall effect (SHE) holds great potential applications in manipulating spin-polarized photons. However, the SHE is generally very weak, and previous studies of amplifying photonic SHE were limited to the incident light in a specific wavelength range. In this paper, we propose a four-layered nanostructure of prism-graphene-air-substrate, and the enhanced photonic SHE of reflected light in broadband range of 0 THz–500 THz is investigated theoretically. The spin shift can be dynamically modulated by adjusting the thickness of air gap, Fermi energy of graphene, and also the incident angle. By optimizing the structural parameter of this structure, the giant spin shift (almost equal to its upper limit, half of the incident beam waist) in broadband range is achieved, covering the terahertz, infrared, and visible range. The difference is that in the terahertz region, the Brewster angle corresponding to the giant spin shift is larger than that of infrared range and visible range. These findings provide us with a convenient and effective way to tune the photonic SHE, and may offer an opportunity for developing new tunable photonic devices in broadband range.