Low cost fabrication of SiO2 optical waveguides by laser direct writing on Ti-doped Sol–Gel films

A commercial direct laser writing (DLW) system operating at 1070 nm was used to fabricate SiO2 optical waveguides on silicon wafers. A Ti-doped SiO2 Sol–Gel film was deposited on the SiO2/Si substrate by the dip-coating technique, based on which SiO2 optical waveguides were patterned by DLW using a Ytterbium fiber laser and followed by chemical etching. The effects of laser parameters and the preheated temperature of Sol–Gel films on the dimensions of optical waveguides were studied systematically. The differences of etching rate between laser irradiated and non-irradiated areas in Sol–Gel films preheated at various temperatures are characterized by measuring the thickness of the films. Results demonstrate that the available laser power density range for laser densification and the width of the patterned optical waveguides are influenced strongly by the preheated temperature of the Sol–Gel films. The width of the optimized optical waveguide in this work is 25 μm. The minimum propagation loss of the fabricated optical waveguides is 1.7 dB cm−1 at the wavelength of 1550 nm.