Implementation of stimulated Raman losses and stimulated Raman gain microscopy using three femtosecond laser sources

Stimulated Raman scattering microscopy allows vibrational contrast mechanism for imaging with high spectral and spatial resolution along with three-dimensional sectioning. In this paper, the implementation of a Stimulated Raman Scattering microscope (SRSM), obtained by the integration of a femtosecond SRS spectroscopy set-up with an optical microscope equipped with a scanning unit, is described. Femtosecond Stimulated Raman Scattering microscope is equipped with three femtosecond laser sources: a Ti:Sapphire (Ti:Sa), a synchronized optical parametric oscillator (SOPO) and a frequency converters for ultrafast lasers, i.e. a second harmonic generator optimized for the SOPO. The proposed implementation allows to cover all the regions of Raman spectra, taking advantage of two different laser combinations. The first, Ti:Sa and SHG laser combination can cover in SRL modality the fingerprint region (500 - 1700 cm) and the silent region. The second, Ti:Sa and OPO, can cover the C-H region or O-H region (2800 - 3200 cm) in SRG modality. In order to demonstrate its successful realization Stimulated Raman Gain (SRG) and Stimulated Raman Losses (SRL) images of polystyrene beads are reported and discussed.