In Kan Laboratory at the University of Electro-Communications, we are conducting research on unique MEMS optical sensors and devices by fabricating micro- to nano-sized metal diffraction gratings and pillar structures on silicon. Normally, silicon alone does not have sensitivity to infrared light, but by utilizing the Schottky barrier formed at the interface between silicon and metal, it becomes possible to electrically detect infrared light with silicon. By absorbing externally incident light with diffraction gratings or pillar structures formed through MEMS processes, it is also possible to selectively detect specific wavelengths or polarizations of light. By utilizing these features, it is possible to construct infrared light detectors using silicon-based devices, as well as to develop spectroscopic sensors, gas sensors, and chemical sensors. Furthermore, by using silicon as the substrate material, it has the advantage of being able to utilize existing semiconductor manufacturing processes and leverage the legacy of semiconductors. This is a highly efficient method in terms of mass production and system integration. In this way, Kan Laboratory is utilizing unique MEMS principles to advance research on ultra-compact, cost-effective optical sensors with simplified manufacturing processes.