composites containing BiB306 glass nanoparticles embedded in polymers

such as polarized illumination or acoustic field [3,4]. Doping with rare earth ions that could be polarized by external fields additionally improves NLO properties of such materials. Further improvement ofNLO properties may be reached by fabrication of glass nanoparticles (NP) and formation of composites consisting of the NP embedded in polymer matrices. Their nonlinear optical properties may be operated by external laser light. The paper describes results of investigations ofNLO properties ofBIBO glass (partially crystallized and in form of fibers) and BIBO glass NP/polymer composites. In the latter case Tm3+, and Pr3+ ions were used for doping of BIBO glass. Polymethylmethac rylate (PMMA) and polycarbonate (PC) were used as polymer matrices. The glassy NP were obtained by means of acoustical field crushing of bulk BIBO glass using the AG201 acoustical generator with power density up to 7 Wcm-2• The obtained NP had size distribution within the range 60-220nm with maximum around 160 and 180 nm for Tm3+ and Pr3+ doped glasses, respectively. In case of partially crystallized BIBO glass and fibers 3.5 MW pulsed single-mode nitrogen laser (A. = 337nm, 't = 50ps ) was used as the source of photo-inducing beam, while Y AG:Nd pulsed laser (A. = 1.06Ilm, 't = 25ps) served as the source of probing beam. Maximal value of second-order optical susceptibility d222 equal to about 5pmIV was obtained for partially crystallized BIBO glass, much higher than in case of BIBO single crystals ( � 3 pm/V). Glasses as a disordered solid state, due to presence of trapping levels located in the forbidden gap giving additional contribution to NLO susceptibilities , are more effective than crystals under influence of photo-inducing illumination. The existence of trapping levels was confirmed by changes of photo­ induced absorption. NLO properties of BIBO glass NP/polymer composites were investigated under bicolor illumination (Y AG:Nd l.064 Ilm radiation and its second harmonics interacting in the volume of the composite sample at a chosen angle -so-called optical poling). During the optical poling &t acentric grating was formed allowing second harmonic generation of fundamental laser beam. It was found that easily polarizing PC matrix provides conditions for effective photo-induced SHG, while low-polarizable PMMA matrix gives much lower NLO response. Concentration of NP in the composite, their level of doping as well as kind of rare earth ion determine the SHG efficiency. The best results were obtained for BIBO glass NP doped with 0.5% of Tm3+ embedded in PC matrix -second-order susceptibilities reached 5 pmIV. Second-order susceptibilities of bulk BIBO:Tm 3+ glasses under the same conditions did not exceed 3 pmIV. The main advantage of such kind of nanocomposites is the possibility of multi-time variation of a given composite NLO susceptibilities in desirable way by appropriate changes of photo-inducing conditions.