Ultra-compact photonic crystal nanocavity-based sensor for simultaneous detection of refractive index and temperature

In this paper, we propose a nanocavity photonic crystal slab (NCPCS) sensor for simultaneous detection of ambient temperature (T) and refractive index (RI) of the surrounding media. 2D-finite difference time-domain (2D-FDTD) approach is employed to run simulations, while the plane wave expansion (PWE) method is used to investigate the band diagram. Transverse magnetic (TM) modes are considered for the band gap calculations. The sensitivity of the proposed structure has been tested by varying background air hole refractive index from 1 to 1.05 in the step of 0.01 and the temperature sensitivity is determined in the range 305 K-330 K. The structure parameters are optimized yielding quality factor (Q) of 3872 , transmission of 97%, and low detection limit of 9.3*10(-5) RIU. For dual-parameter sensing, RI sensitivity of 431 nm/RIU and T sensitivity of 138 pm/K is obtained. The proposed NCPCS sensor exhibits considerable performance enhancements of sensitivity, Q-factor, and detection accuracy in comparison to previously published results.