Characteristics On The Photo-thermal-refractive Glass And Volume Bragg Gratings

Photo-thermo-refractive （PTR） is a silicate optical glass in which a permanentlocalized refractive index modulation for undergoing crystallization of NaF nano-crystalsafter UV exposure followed by heat treatment. PTR glass is a kind of glass-ceramics,andoptical elements recorded in PTR glass has the excellent thermal and mechanicalproperties as that of glass-ceramics, The resistance performance of acid, alkali, corrosion issimilar to that as the general inorganic photosensitive glass, and has a high optical damagethreshold. High efficiency volume Bragg gratings recorded in PTR glass possess highspectral and angular selectivity. Study on PTR glass and volume Bragg gratings will be ofgreat strategic importance in angular filterings with strong selectivity, laser beamcombining, laser beam control, optical detection, spectrum screening, and space-spectraldetection, et al.In this thesis, a PTR glass based on SiO₂-Al₂O₃-ZnO-Na2O （F, Br） glass system isprepared with a two-step melting process. The photosensitivity of PTR glass with UVirradiated dose, heat-treatment temperature and time is investigated using UV-VIS-IRtransmittance spectrum. The crystallization mechanism of PTR glass is studied by theX-ray diffraction （XRD） and differential scanning calorimetry （DSC）. It is demonstratedthat the photosensitive spectrum of PTR glass is from280nm to350nm, the workingspectrum from400nm to2700nm, the optimum nucleation temperature above490℃,crystallization temperature near595℃and the crystalline phase is NaF. Volume Bragggrating （VBG） with the spatial frequency of1000mm-1is recorded in the PTR glass withdirect laser interference patterning and "two-step" heat treatment process. The preparedVBG has a relative diffractive efficiency up to91%, and the angular filtering for lasersystem is demonstrated with the VBG.