Direct writing of planar waveguide devices using ultraviolet light

Ultraviolet (UV) induced Bragg gratings in optical waveguides have been under intense investigation in the past few years, currently leading to commercial applications in fiber based sensor and telecommunication networks. However, the one-dimensional geometry of optical fibers limits the range of possible UV induced index structures and hence also the functionality of devices based hereon. This situation is currently changing, partly due to the large UV induced index changes available when using hydrogen loaded glass1. Large index changes permit direct writing of buried waveguide cores directly in planar silica based thin films, hence expanding the regime of UV induced index structures from one to two dimensions. The potential functionality of UV written optical devices is correspondingly increased.