Abstract
In this work, we report on the correlation between the grain sizes and the photoinduced birefringence in 70 (TeO2-(x))-10 ZnO-10 WO3-5 TiO2-5 Na2O- (x) (x = 0, 1, 2, 3, 4, and 5 mol% Bi2O3 or Pr2O3) glass microcrystallites embedded into the polyvinyl alcohol (PVA) matrices. The microcrystalline glasses with sizes varying within the range 10 to 50 mu m were embedded into the PVA matrices with an amount 30%. The maximal effect exists for Pr-substituted samples while for Bi-substituted composites the effect is lower. The photoinduced effect is caused by bicolor coherent illumination at 1540 nm/770 nm Er: glass with pulse duration 25 ns and was monitored by continuous wave (cw) He-Ne laser at 663 nm wavelength with power about 20 mW. The optimal photoinduced changes were achieved for the two photoinducing beams at angles varying between 12 and 28 degrees. The effects were maximal for x = 0.18. The principal mechanisms are caused by a formation of the structure similar to mesoporous one and are correlated with photoinduced absorption. The dependence on the presence of Pr or Bi ions is studied.