Photonic spin Hall effect in a parity-time symmetric cavity and its sensing application

By inserting an air gap between two epsilon-near-zero dielectric slabs of balanced gain and loss, the parity time (PT) symmetric cavity is established. In this contribution, the scattering behaviors, including reflection and transmission, as well as the photonic spin Hall effect (SHE) in the PT symmetric cavity are investigated. This cavity is found to exhibit a multiple PT symmetry characterized by alternating symmetric and broken phases. This multiple PT symmetry allows the photonic SHE of transmitted light to be easily manipulated in the ranges of broad angles. Near the resonance angle of coherent perfect absorption (CPA)-laser mode, the enhanced photonic SHE of both transmitted and reflected light can reach its upper limitation (i.e. half of the beam waist), which are much larger than that of the PT-symmetric structure without air gap. Finally, a novel sensing scheme based on the photonic SHE enhanced by the excitation of CPA-laser mode in this PT-symmetric cavity is proposed. The results show that this refractive index sensor has a superior intensity sensitivity of 8762 um/RIU, which outperforms the photonic SHE sensors enhanced by surface plasmon resonance. These findings provide an effective method to enhance the photonic SHE and therefore open the opportunity for developing the optical sensors based on the photonic SHE.