Broadband stimulated Raman scattering microscopy (Conference Presentation)

We present several approaches to broadband stimulated Raman scattering (SRS): Fourier-Transform SRS (FT-SRS), Photonic Time Stretch SRS (PTS-SRS) and a multi-channel lock-in amplifier (M-LIA). In FT-SRS the broadband Stokes pulse is sent to a birefringent delay line that creates two collinear replicas, whose interferogram is measured by a single detector. The pump-induced change of the interferogram, measured by a lock-in amplifier, gives, after Fourier transform, the SRS spectrum. In PTS-SRS the broadband Stokes pulse is temporally stretched by an optical fiber to a duration of a few nanoseconds and sampled by a high-frequency analog-to-digital converter, allowing measurement of SRS spectra at MHz repetition rates. Finally, a M-LIA allows sensitive measurement of the SRS spectrum at a number of frequencies from 4 to 32.