Analysis and optimization of MEMS-based Michelson interferometers featuring curved mirrors under partially coherent light conditions

The miniaturized Michelson interferometer has proven to be of importance in many applications, such as spectroscopy, optical coherence tomography, autocorrelation, process control, and telecommunications. Optimizing the device specifications requires proper analysis and understanding of its optical performance under coherent and partially coherent light excitation. In this work, a Gaussian-beam-based model is developed to analyze the performance of the MEMS Michelson interferometer with flat or curved mirrors, accounting for the finite size of the detector aperture. Then, a numerical Fourier optics model is developed to simulate the structure, considering the effects of light divergence and beam truncation throughout the device. The response of the device is simulated over a wavelength range of 1.5 to 2.5 µm. The results of both models agree as they predict an average transmitted power of 5.4% with respect to the input when flat micromirrors are used in the interferometer. Simulations are carried out for both coherent and partially coherent light excitations, where the spatial partial coherence is modeled using the elementary source model. For partially coherent sources, the average transmitted power drops to 4.96% with respect to the input. To improve the limited throughput of the device due to the small size of micromirrors, flat micromirrors are replaced with curved ones. The impact of curved mirrors is explored using both models, yielding an expected increase in the useful output power of more than 3× for a 2<i>m</i><i>m</i>×2<i>m</i><i>m</i> device. The effect of using curved micromirrors on the self-apodization function is also analyzed. It is found that while the power increases by more than 3×, the width of the self-apodization function decreases by more than 4×.