Sub-second low frequency vibrational SRS imaging using a fast acousto-optic delay line

Low frequency vibrations (< 200cm^(-1)) contain the structural information of molecules or the crystal lattice - making low frequency Raman imaging an ideal candidate to analyze heavy molecules, crystal formation etc. The longer integration times of spontaneous Raman spectroscopy, however, limits the study of dynamic structural changes. In our work, we have built a stimulated Raman scattering (SRS) pump probe scheme combining impulsive excitation with a fast acousto-optics delay line. With a pixel dwell time of 25μs, we have acquired, on a shot noise limited detection system, sub second low frequency (< 200cm^(-1)) hyper-spectral SRS images of various samples.