Femtosecond direct written waveguides in Bismuth Germanate

We have identified a waveguide writing regime that allows us to fabricate low loss (-1dB/cm) multimode waveguides in BGO without damaging the surrounding material or by creating a stress field. Fig. 1 (a) shows the micrograph of the cross section of a written waveguide, no damage is visible, the core is elliptical and supports multimode guiding at a wavelength of 1.5 μm.