Giant photonic spin Hall effect empowered by polarization-dependent quasibound states in the continuum in compound grating waveguide structures

The photonic spin Hall effect (PSHE) plays an important role in both fundamental science and precision metrology. In this paper, we theoretically propose a polarization-dependent bound state in the continuum (BIC) in a compound grating waveguide structure based on the selectable guided resonance at near-infrared wavelengths. Empowered by the unique resonant property and polarization-dependent property of the quasi-BIC, the transverse shift of the PSHE can be intensively enhanced to the order of hundreds of micrometers. Besides, the enhancement of the transverse shift of the PSHE is robust against the geometric parameters. Our work not only provides an all-dielectric platform to achieve giant PSHE, but also offers a viable approach to design high-performance PSHE-based optical devices.