Laser processing of channel waveguide structures in sol-gel coatings

Sol-gel derived silica, silica-titania, and tantala coatings were covered with a thin metal film and translated across a Nd:YAG laser beam (1.06 μm). The laser energy was absorbed by the metal film, which heated the underlying sol-gel coating. This heating densified the sol-gel coatings, thereby increasing the index of refraction of the laser heated region, and forming channel waveguide structures in all three systems. The channels formed by this technique were etched, to remove the undensified regions, which resulted in ridged waveguide structures. The structures were also produced by depositing a metal pattern using photolithographic techniques, and rastering the laser across the entire sample. The refractive indicies of laser densified and furnace densified silica coatings were similar. Large differences were observed in the indicies of laser and furnace densified coatings for the silica-titania and tantala systems.