High-performance, low-cost on-chip Fabry-Perot interferometer with microfluidic channel using single anisotropic wet etching

In this paper, we present a design for improving the fabrication process of an in-plane Fabry-Perot interferometer (FPI). The fabrication process involves a single anisotropic etching step in silicon (110) to form a resonator featuring a microfluidic channel and perpendicular structures for fiber alignment. The process etches along the crystalline planes, resulting in an almost perfectly parallel resonant cavity and reducing roughness of optical components. The FPI mirrors consist of two (111) planes coated with a thin film of evaporated gold, enhancing reflectivity. The advantage of this process is that it enables low-cost and commercial fabrication while maintaining high performance. Resonances with Q factor exceeding 2 × 10³ are reported.