Photonic crystal sensor based on Fano resonances for simultaneous detection of refractive index and temperature

Abstract

A structure for simultaneous measurement of refractive index (RI) and temperature (T) is proposed based on photonic crystal (PhC) beam structures. The sensor structure consists of three parallel 1D PhC cavities, in which the middle cavity 1 has a wide linewidth, and cavity 2 and cavity 3 on both sides have a narrow linewidth. By changing the RI of the analyte and the T of the ambient, we explored the linear relationship between the two parameters and resonant wavelengths, respectively. For cavity 2 with air mode, the RI and T sensitivities are 377.2 nm/RIU and 101 pm/K, respectively. For cavity 3 with dielectric mode, the RI and T sensitivities are 194 nm/RIU and 261 pm/K, respectively. In addition, we also discussed the crosstalk between two adjacent cavities at different RI and T, and all crosstalk values are lower than −7 dB and −6 dB for RI and T, respectively. Compared with previous sensor structures, the proposed sensor structure could be used in simultaneous RI and T sensing with higher sensitivity and lower crosstalk values.