Phase-dependent noise in femtosecond pump-probe experiments on Bi and GaAs

Femtosecond laser pulses generate in semimetal Bi and semiconductor GaAs the phonon field that, in addition to being coherent, demonstrates phase-dependent fluctuation properties. The variance of the coherent phonon amplitude, representative of fluctuation properties, is a function of time delay, and the oscillations of the phonon amplitude and its variance occur at different frequencies.