Silicon-on-Insulator (SOI) Ring Resonator-Based Integrated Optical Hydrogen Sensor

We demonstrate a novel, highly sensitive integrated hydrogen sensor based on a silicon ring resonator on the silicon-on-insulator platform. The hydrogen sensitive element in the sensor structure is a platinum-doped tungsten oxide catalytic coating. The catalytic combustion of hydrogen in air leads to a local temperature rise in the ring resonator. The resulting thermo-optic effect shifts the ring resonator resonance. Resonance wavelength shifts higher than a nanometer are measured for hydrogen concentrations below the 4% lower explosion limit. A potentially tunable sensitivity of around 480 pm shift per %H2 is achieved at an operating temperature of about 40degC.