A fiber laser source for parallel dual-window multiplex SRS (DWM-SRS): single-shot CH-stretching and fingerprint imaging

We present the first, to our knowledge, multiplex stimulated Raman scattering system covering simultaneously the CH-stretching region (2800-3100 cm^-1) and the fingerprint (1000-1350 cm^-1) in a single shot. This new approach is called dual-window multiplex SRS (DWM-SRS) and it is based on a novel fiber-based triple oscillator architecture, able to generate three independent passively-synchronized pulse trains. The three outputs are amplified in a master-oscillator-power-amplifier (MOPA) structure in order to reach power levels compatible with SRS microscopy. The two amplified narrowband pump beams, one centered at 792 nm (CH-stretching) and one at 920 nm (fingerprint), are amplitude modulated and overlapped together with the broadband Stokes arm centered at 1030 nm. Each individual pump interacts with the broad Stokes to perform multiplex SRS in a specific Raman window and, thanks to the dual-frequency/quadrature modulation of the two pumps, it is possible to recover the two spectral regions simultaneously with a single multichannel lock-in detector.