SU-8 optical accelerometers

This paper presents the optimization and characterization of SU-8 quad beam optical accelerometers based on intensity modulation. An applied acceleration causes a misalignment between three waveguides, resulting in variation of losses. Mechanical simulations have focused on the evaluation of sensitivity and the design of a robust junction between the mechanical beams and the inertial mass. Results demonstrate that perfectly rounded structures show at least 4.4 times less stress than L-shaped counterparts. Optical simulation predicts that the optimal configuration in terms of sensitivity is obtained when the waveguides are not completely misaligned, since then losses are insensitive to variations in acceleration. Numerical sensitivities ranging between 11.12 and 32.14 dB/g have been obtained. Fabrication has been simplified, now requiring only two photolithographic steps and electroplating Cu as a sacrificial layer. Experimental results show a reproducible experimental sensitivity of at least 13.1 dB/g.