Pb4.7Ba0.3Ge3O11 crystals as new acoustically induced nonlinear optical materials

Acoustically induced optical second harmonic generation (SHG) and two-photo n absorption (TPA) in ferroelectric Pb4.7Ba0.3Ge3O11 crystals have been fou nd. We have found that with increasing acoustical power, the SHG for YAG:Nd laser light (lambda =1.06 mum) increases and achieves its maximum value at acoustical power density about 1.75 W/cm(2). The evaluated SHG values were 23 % less comparing with chi (222) tensor of the KDP single crystals. With decreasing temperature, the acoustically induced SHG signal strongly incre ases below 29 K. The maximal acoustically induced SHG has been observed at acoustical frequencies lying within the ranges 12-17 kHz, 22-23 kHz and abo ve 26 kHz. This behavior reflects nonlinear superposition of the nonlinear optical susceptibilities stimulated by externally-induced electron-phonon a nharmonicity. We have observed substantial increase of the TPA (for the aco ustical power W= 1.8 W/cm(2)) at high hydrostatic pressures (about 16 GPa) and low temperatures (below 16 K). This one confirms complicated influence of the electron-phonon interactions in the ferroelectrics on the observed n onlinear optical dependences.