Double-Layer InSb Photonic Crystal Structure for Enhanced Nonreciprocal OTS and Its Potential in Extending the Measurement Range of Bivariate Sensors

In this article, the dependence of optical Tamm state (OTS) to the refractive index of the interface medium is used to form nonreciprocal absorption peaks after introducing the double InSb layers on both sides of the structure. Compared to the introduction of a single layer, the energy coupling between the double InSb layers is stronger, which greatly improves the absorption performance. The enhancement of the incident angle can significantly regulate the polarization separation of the absorption peak in different directions, and the degree of nonreciprocity will also be affected by temperature and magnetic field. In the opposite direction, the relevant absorption peaks show a differentiated linear range for refractive indexes and incident angles, thereby increasing the measurement range (MR) of dual variable detection. For positive incidence, the MR, sensitivity (S), and detection limit (DL) of refractive index detection are 0.52 THz/RIU, 2.6-3.4 RIU, and 5.5\times 10^{-4} RIU, respectively. The corresponding indicators of angle measurement are successively 0.0074 THz/°, 15-40°, and 0.039°. For negative incidence, the performance indexes of refractive index measurement are 0.81 THz/RIU, 2.1-2.6 RIU, and 3.25\times 10^{-4} RIU in turn. The angle detection characteristics are 0.01 THz/°, 40-76°, and 0.047°. By comparison, the MR of the refractive index sensor is extended by at least 62.5%, while that of the angle sensor rises by 69.4%. We hope that the proposed design is beneficial to the improvement of sensor performances.