Dynamics of coherent plasmon-phonon coupled modes in GaAs using ultrashort laser puises

Abstract Dynamical properties of coherently excited plasmon-phonon systems have been studied by a reflection-type pump-probe technique. Samples used in this study are n-type GaAs. In the present work, using 20 fs ultra short laser pulses, we have observed coherent oscillations of the upper mode (L + ) as well as the lower mode (L − ) in plasmon-phonon systems. The line shape and the peak frequency of the L − and L + bands vary strongly on the photo-excited carrier densities. The dependence of the mode frequencies on carrier density is in agreement with predicted behavior.