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A narrow-bandwidth interference filter has been developed using volume holography in photorefractive LiNbO3 crystals. The device works as a Bragg reflector using a volume hologram recorded, fixed and developed in a LiNbO3 sample. With a 2 mm thick LiNbO3 plate the following performances have been achieved: a peak reflectivity above 32%, a full-width at half-maximum bandwidth below 0.05 nm, an angular field of view of about 3 degrees and a peak wavelength of 518.45 nm (for green Ar laser writing wavelength). These performances compare well with that exhibited by the conventional Lyot-Ohman and Solc filters. A complete explanation of the fabrication procedure is given, including practical details needed for producing such an efficiency with fixed holograms in LiNbO3.

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Changes on the defect structure of Bi12GeO20 (BGO) and Bi12SiO20 (BSO) crystals induced by thermal treatments and laser irradiation have been studied by means of cathodoluminescence in the scanning electron microscope. The results have been compared to those previously reported for untreated and electron irradiated samples and recombination mechanisms responsible for some of the observed luminescence bands are discussed. Annealing of BGO samples causes the appearance of a new luminescence band at about 390 nm. The centers responsible for this band decorate the deformation slip bands in quenched BGO as observed in the cathodoluminescence images. The emission observed in BSO in the same spectral range is quenched during the annealing treatment. The annealing induced reduction of Bi ions to metallic Bi appears to be related to the quenching of a band at 640 nm observed in untreated samples.

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Cathodoluminescence and photoluminescence of Bi 12 SiO 20 and Bi 12 GeO 20 samples are studied. Both kinds of samples show a dark orange central part or core. Emissions in the blue, green, and red spectral regions are observed. The 640 nm band is the predominant feature in the core emission. The evolution of this band during electron irradiation suggests possible emission mechanisms. In addition, two infrared emissions at about 915 and 1390 nm are detected.