45° micro-mirror for out-of-plane coupling of silica-based optical waveguide on si substrate

We describe the fabrication and performance of micro-mirror for silica waveguides on silicon substrate. The micro-mirror consists of four facets, which is produced by wet-etching a pyramid-shaped pit on the backside of the Si-substrate and transferring it to silica waveguide by dry-etching. This mirror couples waveguide light normal to waveguide plane. We developed a trench-filled 0.45Δ% Ge-doped borosilicate glass waveguide by flame hydrolysis deposition method to achieve flat surface all over the mirror facet. We observed from scanning electron microscope (SEM) observations that 45° mirror angle and smooth mirror surface is achieved. The propagation loss of the waveguide including the micro-mirror is measured to be 0.1 dB/cm at 1.55 µm wavelength.