Analysis and modelling of a silicon micromachined Mach-Zehnder interferometer for pressure sensing

This work presents analysis and modelling of a silicon micromachined Mach - Zehnder interferometer for pressure sensing, which is based on optimized layer thickness of a sandwich structure. Sensitivity to pressure is achieved by placing the sensing arm of the interferometer on a thin silicon diaphragm fabricated by micromachining from the rear side of the wafer. We analyse mechanical properties for pressure sensing and we have determined closed-form expressions that can be used as satisfactory tools for the design and optimization of optomechanical pressure sensors based on simple membranes with small deflections. The finite element software package ANSYS was used to compare the results. The relative change of the refraction index in the waveguide was calculated using the stress elasto-optical coefficients for SiON.