Laser operated borate polymer nanocomposites

We have found that UV polarized treatment of the nanocrystals (non-centrosymmetric Li2B4O7 and centrosymmetric α-BaB2O4) embedded into the olygoether acrylate photopolymer samples cause substantially different response depending on the laser features. For the Li2B4O7 NC, during treatment by pulsed 7 ns laser polarized nitrogen laser pulses at 337 nm we observed substantial red spectral shift of the energy gap from 7.3 eV up to 6.3 eV. The spectral shift is disappeared during the 15 min after the interruption of optical treatment. The effect exists only in the nanocrystallites with sizes below 200 nm. At the same time for the centrosymmetrical α-BaB2O4 nanocrystallites this effect was absent. However the photoinduced second order optical effects induced by coherent bicolor treatment by wavelengths 532 nm and 266 nm are enhanced for the α-BaB2O4 NC and are absent for the Li2B4O7 ones.

Research highlights▶ We have established that the borate nanocrysatallites embedded into the photopolymer matrices show drastic dependence on the non-centrosymmetry of the basic crystallites. ▶Using the different laser treatment one can vary the properties of the crystallites in the desirable directions. ▶The technology of the preparation of the novel type of the borate nanocrystallites is presented.