On-Chip Loop-Terminated Mach-Zehnder Interferometer Gas Sensor

On-chip gas sensor using widespread silicon-on-insulator (SOI) technology is presented. The design is based on loop-terminated Mach-Zehnder Interferometer (LT-MZI) which enhance the sensor performance by a factor of two as compared to conventional MZI. Slot waveguide is used to further increase the sensitivity of the gas sensor. Finite difference eigenmode (FDE) solver and finite difference time domain (FDTD) solver were used to optimize and obtain the sensor performance. A figure of merit (FOM) of 230 RIU-1 is achieved with interferometer arms of only 100 µm.