Direct laser writing of thermally stabilized channel waveguides with Bragg gratings

Thermally stabilized photo-induced channel waveguides with Bragg gratings were fabricated in Ge-B-SiO2 thin glass films by exposure with KrF excimer laser and successive annealing at 600 degrees C. The annealing reversed the photo-induced refractive index pattern and also enhanced its thermal stability. The stabilized channel waveguide with a Bragg grating showed diffraction efficiency of 18.0 dB and 18.7 dB for TE- and TM-like modes, respectively. The diffraction efficiencies and wavelengths for both modes never changed after heat treatment at 500 degrees C, whereas the conventional photo-induced grating decayed even at 200 degrees C.