Optically induced effects in nano-crystallized PbO–Sb2O3–B2O3:Pr2O3 glasses

PbO–Sb2O3–B2O3 glasses mixed with different content of Pr2O3 (ranging from 0 to 0.6 mol%) were crystallized. The samples were characterized by X-ray diffraction, transmission electron microscopy (TEM) and differential scanning calorimetric (DSC) techniques. The TEM studies indicated that the samples contain well defined and randomly distributed nanoclusters possessing the sizes within ∼30–40 nm. The XRD spectra have exhibited diffraction peaks due to presence of Pb5Sb2O8, Pb3(SbO4)2, PbB4O7, β-PrSbO4, Pr3SbO7, Pr3Sb5O12 crystalline phases. From these spectra, it was identified that the antimony ions co-exist in Sb5+ state with Sb3+ state in the titled glass ceramic samples. The photo-induced birefringence (changes in refractive indices) caused by simultaneous exposure of the sample with the doubled frequency coherent laser beam (1.54 μm and 0.77 μm) was monitored by polarized probing beam of varying wavelength in the range of 750–1250 nm. The induced birefringence exhibited a maximum at about 1000 nm, a wavelength corresponding to 3H4 → 1G4 optical excitation transition of Pr3+ ion. We have established a correlation between the intensity of this transition and the birefringence dispersion. Principal role of the photo-occupation of this transition is identified. The variations of photo-induced birefringence with increase in the content of Pr2O3 is explained due to the increasing degree of disorder and increasing concentration of deformed PrO8 structural units in the glass ceramic. Further analysis of these results coupled with the data on IR and Raman spectral studies, has indicated that PbO–Sb2O3–B2O3 glasses crystallized with 0.6 mol% of Pr2O3 exhibit maximal birefringence effects.