COHERENT ACOUSTIC PHONONS IN PBTE QUANTUM DOTS

Femtosecond pump-probe studies at 1.5 mu m of PbTe quantum dots in a g lass matrix have revealed oscillations due to a spheroidal acoustic mo de. The wavelength dependence of the observed frequencies indicates si ze selectivity. The frequency and damping of the mode as a function of wavelength agree with the predictions of an acoustic continuum model that suggests that the dominant damping mechanism is radiative loss fr om the dots to the surrounding glass. (C) 1998 American Institute of P hysics. [S0003-6951(98)03241-0].