Buried Sol-gel/SiON Waveguide Structure for Passive Alignment to Single-Mode Fiber on Si Substrate

Buried sol-gel/SiON waveguide structure is proposed for efficient optical coupling to single-mode fiber (SMF) using passive alignment technique on silicon substrate. Difficulties of photolithographic patterning on highly nonplanar surfaces were resolved by fabricating the waveguide devices at a distance from the proximity of deep grooves and by using the sol-gel material for producing negative images of the cores in the buried waveguide structure. A good optical coupling between the waveguide and SMF is obtained by bringing the SMF in close contact to the waveguide facet after saw-cutting the SiON cladding away. The loss due to fiber displacement is about 0.6 dB per facet