Numerical simulation of SU-8 optical accelerometers

This contribution deals with the optimization of a new SU-8 optical accelerometer. Microaccelerometers became large-scale production devices the last 90's. Several working principles have been applied for acceleration sensing. However, most of them suffer from high cross-sensitivity to electromagnetic interferences (EMI) and they cannot be used under harsh/explosive atmospheres. Therefore, optical accelerometers can be used to avoid these drawbacks. We introduced a new integrated polymer optical accelerometer based on intensity modulation formed by a SU-8 polymer structure. The SU-8 polymer is used as structural material but also as optical waveguide. It consists of one mass adjoined to four beams, all of them made of SU-8. There are three aligned optical waveguides: one on the mass and two fixed to the substrate. Any applied acceleration will misalign the three waveguides; the losses show the acceleration level. The paper is focused on the numerical simulation of this device. It is a one-way sequentially coupled analysis. Firstly, a finite element method (FEM) simulation is done to calculate the mechanical sensitivity of the structure. In parallel, the beam profile at the waveguides is computed by using the non-uniform finite difference method (NU-FDM). Finally, the evolution of the light beam in the propagating axis of the waveguides is simulated using the beam propagation method (BPM) by introducing the results of the previous simulations as loads. The good agreement between the experimental results and the simulation demonstrates the feasibility of the sequential couple of the mechanical and optical fields by using the three different numerical methods