Waveguide writing by CO2 laser annealing on sputtered silica film

We present a novel method for creating refractive-index structures in sputtered silica film using CO2 laser annealing. The silica film was prepared by radio frequency magnetron sputtering on silica substrate. Deposited film with the refractive-index 0.8% higher than that of the silica substrate was realized, with a propagation loss of 0.4 dB/cm. The refractive-index of the silica film could be reduced by CO2 laser annealing, enabling the formation of cladding structure for 2-D waveguide.