Optomechanical analysis of silicon integrated optical pressure sensors based on Mach-Zehnder interferometry

This work presents a pertinent optomechanical analysis of various configurations of silicon integrated optical pressure sensors based on Mach-Zehnder interferometry. In principle the analysed sensors are made of a striploaded Mach-Zehnder interferometer (MZI), which is placed on a micromachined rectangular silicon membrane as a pressure sensitive element. The micromechanical MZI operates on the basis of the photoelastic effect (stress-induced change in refractive index) which modulates the phase of light propagating through the active waveguide of the MZI. In order to optimize the integrated optical pressure sensors, analysis and simulation of optomechanical effects including both photoelastic transduction principles and the photonic transport are performed. Taking into account the anisotropic nature of the MZI mechanical and optical properties, the effects of physical and geometrical parameters on sensitivity are described. Single layer and multilayer models for waveguide are also analysed and a comparison between TE and TM modes is performed. Design considerations for MZI structures (with push-pull and non-push-pull configurations) and for single silicon membrane and cascaded silicon membranes are presented. These analyses demonstrate that efficient and high performance integrated optical pressure sensors can be designed and fabricated.