Design, simulation and performance comparison of SoI rectangular waveguide and SMF for methane detection

Sensing analysis of methane gas has been presented in this paper by using Silicon on Insulator (SoI) based gas sensor. Methane a primary component of natural gas and a significant contributor in global warming. Sensing of methane is important because it is highly combustible gas which may leak from the voids of caverns and can explode during mining activities. To avoid fire in underground coal mines optical sensors, need to be designed. To evaluate sensing performance in this research work, gas detectors are investigated using two types of optical waveguides, one is Single Mode Fiber (SMF) and other is SoI based optical rectangular waveguide. These two-waveguide structure works for sensing application of several liberated gases in atmosphere and can detect the presence of methane. However, SoI based rectangular waveguide is more sensitive to the change in the Refractive Index (RI) corresponding to methane volume concentration in air. Further to increase the sensitivity, integrated circuit ring resonator is designed to detect the very low concentration of methane in air. On comparison of SM fiber and SoI waveguide in its straight and ring form, the SoI ring resonator structure is found to be sensitive to similar to 1% methane concentration.