Photonic spin Hall effect and terahertz gas sensor via InSb-supported long-range surface plasmon resonance

The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of left- and right-handed circularly polarized light, holds great potential applications in optical sensors, precise metrology and nanophotonic devices. In this paper, we presented the significant enhancement of photonic SHE in terahertz range by considering the InSb-supported long-range surface plasmon resonance (LRSPR) effect. The influences of the InSb/ENZ layer thickness and temperature on the photonic SHE were investigated. With the optimal structural parameters and temperature, the maximal spin shift of the horizontal polarization light can reach up to 2.68 mm. Moreover, the spin shift is very sensitive to the refractive index change of gas, thus a terahertz gas sensing device with a superior intensity sensitivity of 250000 μm/RIU is proposed. These findings provide an effective method to enhance the photonic SHE in terahertz range and therefore offer the opportunity for developing the terahertz optical sensors based on photonic SHE.