fs-Pulse Synthesis Using Phase Modulation by Impulsively Excited Molecular Vibrations

We report the temporal characteristics of laser radiation transmitted through impulsively excited ${\mathrm{SF}}_6$ and exhibiting sideband Raman lines. Even without special dispersion control we observed a sequence of compressed fs pulses following with the period of the excited $A_{1g}$ vibrational mode of ${\mathrm{SF}}_6$. The use of both negative and positive group velocity dispersion compensation for the temporal compression was found to be as appropriately efficient. The results prove our new concept of the ultrafast molecular phase modulator.