Anti-External Interference Sensor Based on Cascaded Photonic Crystal Nanobeam Cavities for Simultaneous Detection of Refractive Index and Temperature

In this paper, we present an anti-external interference sensor based on cascaded silicon-on-insulator ellipse stack major axis modulated photonic crystal (PC) nanobeam cavities. Two PC nanobeam cavities, one covered with SU-8 cladding (cav1) and the other exposed to air directly (cav2), are cascaded to detect refractive index (RI) and temperature simultaneously. Three-dimensional finite-difference time-domain simulations are used for our analysis. We prove the feasibility to obtain RI and temperature simultaneously, obtaining an RI sensitivity of 0 nm/RIU (refractive index unit) and a temperature sensitivity of –107.9 pm/K for cav1, whereas an RI sensitivity of 354.6 nm/RIU and a temperature sensitivity of 46.7 pm/K for cav2. Particularly, the proposed sensor not only achieves competitive RI sensitivities and temperature sensitivities, but also increases the differences between the sensitivity ratios of RI sensing and temperature sensing, which makes the dual-parameter detection easier. Furthermore, we propose the concept and analysis of anti-external interference to describe the ability to resist the external interferences. Based on this analysis method, the proposed sensor achieves a strong anti-external interference ability. Therefore, the proposed sensor is potentially a promising platform for future application of dual-parameter sensing.