Refractive Index Sensing Performances of a Mid-Infrared Asymmetric MZI Based on Suspended GaAs Waveguides

Abstract

A novel mid-infrared (MIR) biochemistry sensor using two suspended GaAs waveguides based on an asymmetric Mach-Zender Interferometer (MZI) is proposed. The propagation properties and refractive index (RI) sensing performances of MZI are investigated by the finite element method (FEM). The simulation results show that the maximum waveguide sensitivities (Swg) of the TE and TM modes in the suspended GaAs waveguide are ∼ 1.2 and ∼ 1.0. This design of the GaAs waveguide using the suspension structure is to enhance the interaction between the vanishing field and measured material. The RI sensitivity of the asymmetric MZI structure increases with the length of the sensing arm, which can reach 854.5 nm/RIU with a Q of 208.2 after parameter optimization. The two arms of the MZI are designed as width-asymmetric structures to make the sensor more sensitive to the measured material. The asymmetric MZI sensing structure has high RI sensitivity and compact structure, which provides a feasible scheme for biochemical sensing.