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Fabrication of SiO2-TiO2 strip waveguides by laser direct writing

SiO2-TiO2 strip optical waveguides have been fabricated by laser densification of SiO2-TiO2 sol-gel films using a Ytterbium fiber lasers and following chemical etching process. Effects of laser processing parameters and dried temperature of SiO2-TiO2 sol-gel films on the dimensions of strip optical waveguides were systematically studied. And the mechanism on laser densification of SiO2-TiO2 films was discussed. The experimental results demonstrate that the width and thickness of strip waveguides increase with laser power density until SiO2-TiO2 films are damaged by laser irradiation. The available range of laser power density for laser densification increase through enhancing dried temperature of SiO2-TiO2 films, which mainly thanks to the increasing stress capacity in the films. The width of strip optical waveguides can be markedly decreased from 110 to 25 μm in the case of the same thickness by enlarging available range of laser power density. The mechanism on laser densification of SiO2-TiO2 films is mainly based on shrinkage of nanoscale pore within SiO2-TiO2 films duo to the energy transferred from silicon substrate.