Demonstration of a directly written directional coupler using UV-induced photosensitivity in a planar silica waveguide

The authors report, for the first time, the demonstration of a UV directly written directional coupler in a planar silica waveguide on silicon. From the device parameters and the measured spectral characteristics, the UV-induced index change is calculated to be 0.0075. This is the highest photoinduced refractive index change reported to date in a planar silica waveguide.