Highly sensitive refractive index, chemical potential, and applied electrical voltage detection in terahertz region with photonic spin Hall effect in a plasmonic sensor based on graphene and germanium layers

Abstract

"In this work, a transverse spin-dependent shift (SDS) of the horizontal photonic spin Hall effect (PSHE) at a fixed frequency (5 THz) is simulated for detection of refractive index, chemical potential, and applied electrical voltage to a plasmonic sensor with four layers (germanium, organic layer, graphene, and gas medium). The variation of the refractive index of graphene with chemical potential and applied voltage is given from the simulated values. A refractive index resolution (1.73 × 10–12 RIU) is obtained when the refractive index n4 of the analyte layer is changed from 1 RIU to 1.1 RIU when the chemical potential μc is 0.003 eV and the amplified angle ∆ is 0.1°. A chemical potential resolution (6.32 × 10–14 eV) and corresponding voltage resolution (6.83 × 10–13 V) are obtained when the chemical potential is changed from 0.003 eV to 0.03 eV, the refractive index of gas medium n4 is 1.1 RIU and the amplified angle is ∆ = 0.1°. These values are very good in comparison with the situation when the spin Hall effect is not applied (7.47 × 10–6 RIU, 0.001166 eV, and 0.01259 V) for the same values of μc, n4, and ∆."