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We report the use of CO2 laser heating for inducing an increase in the refractive index of germania doped silica films. UV absorption spectroscopy and XPS analysis have confirmed that the index change is a result of GeO2 being reduced to GeO. The technique has been successfully used for the direct writing of integrated optical strip waveguides.

A plasma activated chemical vapour deposition (CVD) technique is described for fabricating doped silica optical waveguides on silica substrates.Planar, germania doped, silica waveguides have been fabricated with less than 0.3 dB /cm attenuation at X = 0.633 µm.There is considerable scope for reducing the attenuation much further. Waveguide depositions are normally carried out at 1100 °C but guiding films have also been deposited at room temperature.