Abstract
Stimulated Raman Scattering (SRS) imaging can be hampered by non-resonant parasitic signals that lead to imaging artifacts and eventually overwhelm the Raman signal of interest. Stimulated Raman gain opposite loss detection (SRGOLD) is a three-beam excitation scheme capable of suppressing this nonlinear background while enhancing the resonant Raman signal. We present here a compact electro-optical system for SRGOLD excitation which conveniently exploits the idler beam generated by an optical parametric oscillator (OPO). We demonstrate its successful application for background suppressed SRS imaging in the fingerprint region. This system constitutes a simple and valuable add-on for standard coherent Raman laser sources since it enables flexible excitation and background suppression in SRS imaging.
Highlights
Coherent Raman scattering (CRS) microscopy [1] is a class of optical imaging techniques based on the photo-stimulation of molecular vibrations
Coherent anti-Stokes Raman scattering (CARS) [4] and stimulated Raman scattering (SRS) [5,6] are the most commonly used in vibrational imaging
In order to validate the capability of the Stimulated Raman gain opposite loss detection (SRGOLD) system to suppress artefacts and enhance the Raman signals we image different samples, such as polymer, crystalline and biological samples
Summary
Coherent Raman scattering (CRS) microscopy [1] is a class of optical imaging techniques based on the photo-stimulation of molecular vibrations. In frequency-modulation SRS (FM-SRS), two images (on and off the targeted resonance) are simultaneously acquired and any spectrally flat contribution to the signal is suppressed This type of excitation has been implemented with picosecond sources by either using two optical parametric oscillators (OPOs) [10,22] or by adding a fiber amplifier to the OPO [17]. A different excitation scheme based on the simultaneous detection of the stimulated Raman gain and loss (SRGOLD) has been proposed to suppress non-resonant background and enhance the resonant signal [12]. SRGOLD excitation requires three beams at different frequency: ω0 − Ω, ω0 and ω0 + Ω One main advantage, it can be implemented with the same OPO source commonly used in SRS and CARS microscopy, by exploiting the usually neglected idler beam.
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