Polydimethylsiloxane (PDMS) Coated Broadband Tunable Vanadium Dioxide (VO₂) Based Linear Optical Cavity Temperature Sensor

Silicon on insulator (SOI) based sensors provide a reasonable solution to the issues common in traditional linear optical cavities such as wavelength dependant nature of mirrors, size, and maintaining the resonant condition. In this study we presented polydimethylsiloxane (PDMS) coated SOI based linear optical temperature sensing resonator model and analysed it in finite element method by using COMSOL Multiphysics. The phase changing material (PCM) VO₂ on each side of the Si waveguide helped to achieve the resonant condition and thermal tunability of the resonator. An almost linear variation in resonant frequency (wavelength) f_r due to the temperature change in the range of 0–90 °C resulted in maximum sensitivity of 0.01 THz/°C or 79.4 pm/°C for the 10 µm cavity length. The recorded sensitivity is at least 5-times (or more) higher than the previous studies. The prominent reasons behind this improvement can be PDMS coating, adequate light matter interaction and proper confinement of resonating mode. The demonstrated sensor model has wide operational frequency range spanning from 10 to 210 THz. Moreover, the reported model also showed an increase in temperature sensitivity from 0.00967 to 0.01 THz/°C while the length of resonator was changed from 2 to 10 µm.