Simultaneous measurement of refractive index and temperature using cascaded side-coupled photonic crystal nanobeam cavities

Abstract

We present the design, fabrication, and characterization of cascaded side-coupled Silicon-on-Insulator (SOI) photonic crystal (PhC) nanobeam cavities for simultaneous measurement of refractive index (RI) and temperature. Due to the different mode distribution in air-mode cavity and dielectric-mode cavity, the two types of PhC nanobeam cavities have quite different sensitivities towards the changes of ambient RI and temperature. We demonstrated the feasibility to obtain RI and temperature simultaneously with a single measurement, obtaining a RI sensitivity of 254.6 nm/RIU (refractive index unit) and a temperature sensitivity of 30.1 pm/°C for air-mode cavity, while a RI sensitivity of 105.5 nm/RIU and a temperature sensitivity of 56.4 pm/°C for dielectric-mode cavity.