Development of Large-Range Rotary Interferometer using a Genetic Algorithm for Miniature FTIR Spectrometer

This study innovatively proposes a MEMS interferometer structure integrated with a rotary comb actuator and four corner cube mirrors for the application of Fourier transform infrared (FTIR) spectroscopy. Two orthogonally distributed corner cube mirrors are rotationally actuated by rotary comb actuators, capable of generating a differentially amplified optical path difference. To achieve a larger angular displacement at a lower actuation voltage, the support spring, as the critical part of the rotary comb actuator, is optimized with a curved configuration affording a low twisted flexibility and a high lateral stiffness. The genetic algorithm (GA)-based design methodology is introduced for optimization by a parametrized mechanical model analysis in finite element simulation and a GA in scientific computing. Finally, the functional structures including the rotary comb actuators and the corner cube mirrors are fabricated from a monolithic SOI wafer. The miniature interferometer can provide a large optical path difference of 81.5 μm at an actuation voltage of 55 V, which is applicable in the field of FTIR spectroscopy.