Photo-thermo-refractive glass with sensitivity to visible and near IR radiation

Abstract

Photo-thermo-refractive glass (PTR glass) is a multicomponent silicate glass doped with Ce3+, which changes its refractive index after exposure to UV radiation followed by thermal development. It is extensively used for recording of trivial holograms (volume Bragg gratings) operating in the visible and near IR spectral regions. Ability to record complex holographic structures in PTR glass is of utmost interest as it would be advantageous for imaging and laser beam control applications. However, since photosensitivity of PTR glass is limited to the UV region, complex holograms for the visible and IR applications could not be recorded in PTR glass. To extend PTR glass sensitivity towards longer wavelengths the same glass matrix was doped with terbium, and then an excited state absorption mechanism was used for two-step excitation of the 5d14f7 band of Tb3+ ions by concurrent illumination by long wavelengths (449, 522, 808 or 975 nm) and UV (375 nm) photons. For the first time refractive index modulation exceeding 2 × 10−4 was observed after exposing the material to blue, green and near IR laser radiation. Complex holograms operating in the blue and green spectral regions were recorded in Tb-doped PTR-glass.