CsLiB6O10 crystallites embedded into olygoether photopolymer matrices as new materials for acoustically induced nonlinear optics

Acoustically induced optical second harmonic generation (SHG) in CsLiB6O10 (CLBO) nanocrystallites incorporated into the olygoether photopolymer matri ces has been revealed at liquid helium temperature (4.2 K). The SHG has bee n measured for the source wavelength of an YAG-Nd laser (lambda = 1.06 mu m ). With increasing acoustical power, the SHG signal increases and achieves its maximum at acoustical intensity of about 18.1 W/cm(2) and frequency of about 14 kHz. The value of the SHG chi(222) tensor component was comparable with the one for the traditional nonlinear optical crystals such as KH2PO4 , KTiOPO4, LiNbO3. With decreasing temperature (below 28 K) the acousticall y induced SHG signal strongly increases. A correlation between the acoustic ally nonlinear optical response and low-frequency Raman intensities has bee n found. The maximal acoustically induced SHG has been observed for the nan ocrystallite concentration of about 3.1% (in weight units) and the nanocrys tallite sizes lying within 35-40 nm. The SHG tensor coefficients were large r than for the bulk CLBO crystals (at least 13%). Advantages and drawbacks of the presented model are discussed. The theory of the observed phenomena is explained on the grounds of the ab initio band energy calculations with taking into account anharmonic electron-phonon interactions. (C) 2000 Elsev ier Science B.V. All rights reserved.