A New Technique for Measurement of Raman Dephasing Dynamics and Recent Advances in cw Mode-Locked Dye Lasers

Abstract

Recent advances in the development of synchronously mode-locked cw dye lasers have permitted the first low power measurement of the time resolved dephasing dynamics of a Raman active ground state molecular vibration. Excitation and delayed probing of a coherent ensemble of vibrators is accomplished with the help of synchronized picosecond pulse trains from two independently tunable mode-locked dye lasers. A new probe technique, based on a Raman gain messurement, is employed that provides a signal that scales linearly with the coherent vibrational amplitude. We demonstrate this technique with the first measurement of the dephasing of the ν1 (656.5 cm-1) of CS2 in the liquid state. An exponential decay time of 20 ± 1 psec is obtained for the isotropic contribution to the coherent scattering.