NITROGEN-DOPED GERMANIA GLASSES WITH ENHANCED OPTICAL AND MECHANICAL-PROPERTIES

A new type of ultraviolet photosensitive germanium doped glass has bee n developed for use in the fabrication of optical waveguide structures . By adding ammonia to the source gases during a plasma enhanced chemi cal 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 e ven larger changes in the refractive index can be induced. Stable glas ses with refractive indexes from 1.460 to 1.518 have been formed throu ghout the composition range from 0 to 30% germanium by including ammon ia in the deposition process Not only is it possible to increase the p hotosensitivity, but it is also possible to control stress in these fi lms. Depending on the deposition and annealing conditions, these glass films can be made to exhibit a range of stress from compressive to lo w tensile when deposited on silicon wafers.