OPTICAL CONTROL OF COHERENT OPTICAL PHONONS IN BISMUTH-FILMS

Interference of impulsively excited coherent phonons in semimetals has been studied by using a double-pulse pump-probe technique. Enhancemen t of the oscillation amplitude of an A(1g) mode is observed when the s eparation time of the double-pulse is matched to the period of the pho non oscillation, and a cancellation is observed when the separation ti me is adjusted to half the period of the phonon oscillation. The ampli tude after the second pulse shows a sinusoidal dependence as a functio n of the separation time, and this dependence is explained in terms of a superposition of two coherent phonon oscillations. In addition, not only the A(1g) mode but also an E(g) mode have been observed by elect ro-optic sampling. (C) 1996 American Institute of Physics.