Mid Infrared Integrated MZI Gas Sensor Using Suspended Silicon Waveguide

A novel mid-infrared (MIR) gas sensor is proposed. A sensitivity analysis of the suspended silicon waveguide for gaseous medium index change in the MIR range is also presented. The analysis shows that a suspended silicon waveguide achieves a high sensitivity with a minimal mode loss, which allows the design of a high performance Mach Zehnder interferometer (MZI) gas sensor using a suspended silicon waveguide structure. Two designs are proposed and optimized using the three-dimensional finite difference time domain solver. The first design is optimized for a wavelength interrogation scheme. This design, exhibits a high wavelength sensitivity S = 7028 nm/RIU and a high figure of merit (FOM) of 180 RIU
^-1
for both the wavelength and intensity interrogation methods with a sensing length L
_sens
= 250 μm. The second proposed design is optimized for the intensity interrogation scheme and enhances the intensity interrogation FOM to reach 370RIU
^-1
. This design, based on suspended MZI, is less sensitive to wavelength variations. Our proposed sensors offer simple, low cost, and mass scale fabrication which makes them suitable for lab on a chip technology.