Novel sol-gel material for fabrication of a long period waveguide grating filter as a precise thermometer

A new kind of organic-inorganic hybrid HfO 2/SiO 2 sol-gel material with a large thermo-optic coefficient and a wide linear tunable temperature range has been developed for fabrication of a long period waveguide grating (LPWG) filter,whose parameters were optimized and designed by using finite difference time domain (FDTD) simulations.The LPWG filter,a periodic rectangle-corrugated grating structure,was easily fabricated with soft-lithography technique.At a temperature range from 19°C to 70°C,the fabricated LPWG filter element demonstrated a high temperature sensitivity of about 6.5 nm/°C and a wide linear tunable temperature range of 51°C,so that it can be used as a precise thermometer.Our results are useful for the designs of LPWG filters for the implementation of a wide range of thermo-optic functions.