Abstract

Recently, it has been shown that coherent optical phonons can be excited in semimetals[1,2], semiconductors[2-4] and superconductors[5]. In all cases, pulses of laser light, which are short compared to the optical phonon period, are used to impulsively generate the coherent lattice vibrations. While the experimental methods for phonon excitation are similar, the physical mechanisms responsible for phonon generation appear to differ among the various materials types. For semimetals and narrow-gap semiconductors, the reflectivity modulation observed with the pump-probe technique have been particularly large (on the order of 10% in some materials) and have suggested significant modulation of the material's electronic structure. In these cases, we have determined that the coherent phonon excitation is caused by a mechanism we call Displacive Excitation of Coherent Phonons (DECP) [2,6].

© 1994 Optical Society of America