Reduction of scattering from a glass thin‐film optical waveguide by CO₂ laser annealing

Laser annealing with a CO₂ laser is utilized to improve the quality of Corning 7059 glass thin‐film optical waveguides. The 1.0‐μm‐thick 7059 glass film is deposited by sputtering onto a thermally oxidized silicon substrate. Measurement of the absorption coefficient of 7059 glass at λ = 10.6 μm yields a value of 1.12 x 10⁴ cm⁻¹. Dark‐field photomicrographs taken before and after laser annealing imply that both surface defects and bulk inhomogeneities are removed by laser annealing. Waveguide attenuation is measured to be 17.4 dB/cm befor laser annealing and 0.6 dB/cm afterwards.