AN ABSORBING LAYER FOR MINIMISING SUBSTRATE EXPOSURE DURING THE UV WRITING OF A WAVEGUIDE GRATING IN ADDITION TO A BIREFRINGENT CONTROL SYSTEM

摘要

A waveguide having photosensitive properties is disclosed comprising: a waveguide substrate (2); a first cladding layer formed on the waveguide substrate; a UV absorbing layer (9) formed on the first cladding layer; a UV sensitive layer (4) having optical transmission properties adapted to be changed with UV irradiation, the layer formed on or closely adjacent the UV absorbing layer; and a second cladding layer, being substantially UV transparent, on the UV sensitive layer. Preferably, there is further provided a third cladding layer intermediate of the UV absorbing layer and the UV sensitive layer. The UV absorbing layer comprises a germanosilicate material. The absorbing layer can be adapted to change a physical property upon UV absorption. The UV absorbing layer can be variable thickness, the thickness being in accordance with predetermined requirements.