TIME-RESOLVED NONLINEARITIES FROM NONSYMMETRIC POLAR PHONONS IN PBTIO3 AND KNBO3 PEROVSKITES

We present time-resolved measurements of low-frequency nonsymmetric ph onon polaritons driven impulsively in perovskite crystals. The definit ion of the phonon wave vector as a function of the excitation waveleng th is addressed for the case of one and two pump beams. Results obtain ed with KNbO3 and PbTiO3 for B-2 and E symmetry modes, respectively, a re presented, and the value of the lowest wave vector that can be reac hed for a specific wavelength of the pump beams is discussed. (C) 1996 Optical Society of America