Femtosecond material response probed by phase-stabilized optical heterodyne detected impulsive stimulated Raman scattering

Femtosecond material response of several liquid samples were measured with use of a newly developed "phase-stabilized" optical heterodyne detected impulsive stimulated Raman scattering (ISRS) spectrometer. In this apparatus, the ISRS signal generated with ordinary transient grating geometry is mixed with femtosecond optical pulses (local oscillator, LO) in an interferometer, and the interfered intensity is detected. The subwavelength-accuracy adjustment/stabilization is achieved for the optical path length in the interferometer so that the relative optical phase between the ISRS signal and LO can be controlled. The ISRS signals linearized to each tensor element of the third-order response function were obtained, and discussed.