Nitrogen doped germania glasses with enhanced optical and mechanical properties

A new type of ultraviolet photosensitive germanium doped glass has been developed for use in the fabrication of optical waveguide structures. By adding ammonia to the source gases during a plasma enhanced chemical vapor deposition of these glasses, ultraviolet induced refractive index changes of up to 3.5 x 10(-3) have been obtained.

Although this is, to the best of our knowledge, a record for germanium doped silica films not photosensitized by hydrogen loading, our results show that even larger changes in the refractive index can be induced. Stable glasses with refractive indexes from 1.460 to 1.518 have been formed throughout the composition range from 0 to 30% germanium by including ammonia in the deposition process Not only is it possible to increase the photosensitivity, but it is also possible to control stress in these films.

Depending on the deposition and annealing conditions, these glass films can be made to exhibit a range of stress from compressive to low tensile when deposited on silicon wafers.