An optical ammonia gas sensor with adjustable sensitivity using a silicon microring resonator covered with monolayer graphene

Integrated optic ammonia gas sensor using graphene covered silicon microring resonator is proposed. Ammonia gas adsorption increases the Fermi energy of graphene. The gas concentration is detected by the resonant-wavelength shift of microring resonator. The NH3 gas concentration from 0.5 to 1000 ppm is shown to be measured by the resonant wavelength from 1551.75 to 1551.27 nm. By applying voltage to the graphene, the Fermi energy is controlled to adjust the sensitivity and the range of detectable concentration.