All-optical Mach-Zehnder interferometric NH_3 gas sensor based on graphene/microfiber hybrid waveguide

摘要

In this paper, we report an all-optical NH_3 gas sensor based on graphene/microfiber hybrid waveguide (GMHW). The study on the sensing mechanism shows that as the adsorption of NH_3 modifies the conductivity of graphene and thus the effective refractive index of the GMHW, and the transmitting light along the GMHW is very sensitive to NH_3 gas concentration. The wavelength shift induced by the NH_3 absorption is spectrally demodulated by using a microfiber-based Mach-Zehnder interferometer (MZI). A high sensitivity of ～6 pm/ppm is obtained for the NH_3 adsorption measurement. The resolution of such a sensor is ～0.3 ppm, mainly limited by the resolution of the optical spectrum analyzer used. The work of this paper may open a window for the development of novel GMHW-based gas sensors with high sensitivity, small footprint, easy fabrication and low cost.