Phase-stabilized optical heterodyne detection of impulsive stimulated Raman scattering

An optical heterodyne detection of impulsive stimulated Raman scattering (ISRS) has been carried out for liquid samples using a 50 fs mode-locked Ti:sapphire laser as a light source. In this measurement, the optical path length in the interferometer was actively adjusted while monitoring the interference of a reference laser so that the relative optical phase between the ISRS signal and the local oscillator was stabilized. This method enabled us to obtain the ISRS signals which are linearized to the third-order material response function. The changes in the ISRS signal with the change of the heterodying phase and the polarization condition are discussed.