Novel process for the production of large, stable photosensitivity in glass films

Germanosilicate glasses exhibit a significant photosensitive response which has been linked to the presence of oxygen-deficient germanium point defects in the glass structure. Based on this correlation, a process which produces highly photosensitive thin films without the use of hydrogen exposures, has been developed. This process, applicable to a wide range of desired xGeO2:bf>(1-x)SiO2 film composition, uses reactive atmosphere sputtering and allows extensive control of the degree of oxidation of the films during synthesis to produce dramatic demonstrations of photosensitivity. In preliminary tests, our films demonstrated ultraviolet-induced refractive index perturbations (Δn) of up to -4×10-3 in the visible and -0.4×10-3 at 1.5 μm. Since no hydrogen exposure was necessary, this process yielded stable films which retained their predisposition for large photosensitivity for over one year of storage.