SiC thin-film Fabry-Perot interferometer for fiber-optic temperature sensor

Polycrystalline SiC grown on single-crystal sapphire substrates have been investigated as thin-film Fabry-Perot interferometers for fiber-optic temperature measurements in harsh temperatures. SiC-based temperature sensors are compact in size, robust, and stable at high temperatures, making them one of the best choices for high temperature applications. SiC films with thickness of about 0.5-2.0 μm were grown at 1100°C by chemical vapor deposition (CVD) with trimethylsilane. The effect of operating temperature on the shifts in resonance minima, Δλ_m, of the SiC/sapphire substrate has been measured in the visible-infrared wavelength range. A temperature sensitivity of 1.9×10^-5/°C is calculated using the minimum at ∼700 nm. Using a white, broadband light source, a temperature accuracy of ±3.5°C is obtained over the temperature range of 22°C to 540°C.