A wafer-level miniaturized Michelson interferometer on glass substrate for optical coherence tomography applications

The wafer-level fabrication of a Michelson interferometer using optical MEMS technologies is presented. The intended application is in Optical Coherence Tomography (OCT). The micro fabrication involves two steps: the 45° saw dicing of glass substrate and the subsequent deposition of a dielectric multilayer and metallic layers to obtain a beam splitter and waveguide micro mirrors, respectively. The Michelson interferometer was designed for use in the near-infrared range of 800-900 nm. A 50/50 non-polarized beam splitter was obtained with only four layers (using titanium dioxide and silicon dioxide). The micro mirrors for the required spectral range were fabricated by sputtering of chromium and gold layers. The dicing cuts, which were performed with a custom-made 45° dicing blade, resulted in smooth slopes. The surface's roughness is 19.76 nm at setting and can be reduced to approximately 50% with a soft additional dicing cut. The height of the 45° surfaces was approximately 400 μm, which is in accordance with the design. The micro Michelson interferometer can be easily integrated with other optical components into a complete OCT miniaturized system.