Refractive Index Change of Ge-B-codoped SiO2 by 248nm KrF Laser for Waveguide Bragg Grating Devices

Abstract

Waveguide Bragg Grating is fabricated by the induction of periodical refractive index change in the core layer with a large concentration of Germanium when is exposed to UV light. In this study, photosensitivity dynamics in glass with the composition similar to that of Planar Lightwave Circuit devices was investigated as a fundamental study prior to the device fabrication. Silica bulk glasses for the core layer of PLC devices were prepared in a way that the amount of SiO2, GeO2, and P2O5 were kept constant but the amount of Boron is controlled. The glasses are irradiated by 248nm KrF laser and induced-refractive index changes are measured by prism coupler. It was observed that index variation was reached its maximum of 10-3 , even at total fluence as low as 400J/cm2 and thermal annealing experiment revealed that this variation was due to internal stress.