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 0.45Delta% 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 45deg 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 mum wavelength.