▎ 摘　　要

An integrated optic ammonia gas sensor using a 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 the microring resonator. The NH3 gas concentration from 0.5 to 1000 ppm is shown to be measured by the resonant wavelength from 1 551.75 to 1 551.27 nm. By applying voltage to the graphene, the Fermi energy is controlled to adjust the sensitivity and the range of detectable concentration. (C) 2019 The Japan Society of Applied Physics