A theoretical proposal of photonic crystals with gradient superconducting thicknesses for sensing applications

In this paper, a refractive index (RI) sensor with superconducting photonic crystal in the terahertz regime is theoretically analyzed by the transfer matrix method. An asymmetric resonance cavity containing gradient thicknesses of the superconducting layer is employed to suppress the resonance absorption linewidth. We present the coupled wave theoretical model to give an optimization scheme for excellent sensing performance. The proposed sensing models can achieve an excellent single resonant peak when the temperature is over 80K. When the incident angle varies between 50 degrees and 70 degrees in TE mode, the shift of a single resonant peak has a linear relationship with the incident angle. The simulation results report that the sensitivity and figure of merit in the optimal model can reach over 22.2 mu mRIU(-1) (RIU represents RI unit) and 265 at the ultralow temperature (85K), respectively. Its performance indicators are dozens of times those of the traditional photonic crystal RI sensor. Our study provides theoretical guidance for the design of a low-temperature RI sensor with a high-performance indicator. Published under an exclusive license by AIP Publishing.

Automated summary

In this study, a RI sensor with superconducting photonic crystal in the terahertz regime was theoretically analyzed by the transfer matrix method, presenting an asymmetric resonance cavity and coupled wave theoretical model for optimization. The proposed sensing models achieve excellent performance over 80K, with sensitivity and figure of merit reaching high values at ultra-low temperatures. The performance indicators of the optimized model are dozens of times those of traditional photonic crystal RI sensors, providing theoretical guidance for the design of high-performance low-temperature RI sensors.