Photo-thermo-refractive glasses for high-efficiency Bragg gratings in UV, visible, and IR regions

Summary form only given. The wide spread use of holographic elements is constrained by the lack of available holographic materials. Hariharan´s recent book notes that among the photosensitive materials available for high efficiency hologram recording, each have merits, as well as drawbacks. This paper describes properties and performance of inorganic glass as a medium for volume hologram recording, which meets most requirements cited. The use of inorganic photosensitive glasses for phase hologram recording was described several years ago. The two-step process of exposure to UV radiation and thermal development (photo-thermo-refractive process) has been used to record phase patterns in glass defined as photo-thermo-refractive (PTR). Relative diffraction efficiency of up to 90% was recorded at that time, however, strong scattering from the thermal development process resulted in a low absolute diffraction efficiency, not exceeding 45%.