Novel micromirror for vertical optical path conversion formed in silica-based PLC using wettability control of resin

A novel technique has been developed for fabricating a micromirror in a single-mode silica-based planar lightwave circuit (PLC), in which the flat slope for the mirror is made of resin by utilizing wettability control and the surface tension effect. It was shown that the mirror could be designed by numerical calculation based on the equation of Young and Laplace for a liquid surface. A controllable mirror angle range from 30 to 60 degrees was achieved experimentally by changing the position of the boundary line between high and low wettability regions using oblique evaporation. The characteristics of a fabricated 45 degrees mirror installed in a silica-based PLC were evaluated by coupling it vertically to a single-mode fiber. The obtained coupling losses between waveguides and a fiber were 0.60-1.15 dB for mirrors with widths of more than 200 mu m, and 0.92-1.62 dB for 190 mu m wide mirrors, at a wavelength of 1.55 mu m. The experimental minimum losses of 0.6 and 0.92 dB coincided with the calculated values.