Abstract

Perovskite PbTiO₃ is tetragonal $\left({\text{C}}_{4\text{v}}^1\right)$ in its ferroelectric phase. Its lattice dynamics[1,2] reveals the existence of two (A₁. + E ) Raman active polar modes in the low frequency spectral range (lower than 200 cm^-1). We show that the use of femtosecond pulses in a nonlinear spectroscopy technique^[3,4] is well suited to drive coherently these phonon modes and measure their dispersion.

© 1990 Optical Society of America