Distortion of Gaussian beams reflected off-axis on curved mirrors in the MEMS scale

The recent technological development in the MEMS technology lead to the production of curved micromirror with full three-dimensional control. Understanding how the optical beams are transformed on curved micromirrors is yet to be fully understood in such a scale, where the optical beam spot size is comparable to the micromirror radius of curvature. A numerical study of Gaussian beam distortion upon reflection on micro-curved surface is carried out in this work in the near-infrared spectral regime. The physical-optics approach is used as a benchmark for the Gaussian-optics approach. For the case of 45-degree incidence on a spherical micromirror with a 500-µm radius of curvature, the Gaussian-optics approach shows good accuracy for beam minimum waist radius of 5 µm located in the focal plane of the mirror, while for a minimum waist radius of 1.5 µm the Gaussian optics approach fails to predict the reflected beam profile and divergence angle. The accuracy of prediction for the 5-µm waist radius case is reduced, when the incident beam waist is located farther from the mirror.