A fiber-compatible fiber optical parametric oscillator with a fixed repetition rate and improved robustness for stimulated Raman scattering microscopy

Stimulated Raman scattering (SRS) microscopy is regarded as a powerful vibrational imaging method that requires two-color picosecond pulse trains, one with ultralow intensity noise and the other with wavelength tunability. We previously demonstrated a fiber optical parametric oscillator (FOPO) that can be synchronized with a Ti:sapphire laser to realize low-noise SRS imaging while extending the tunability. However, a free-space cavity of the FOPO requires careful alignment, which limits mechanical stability and compactness. Here, we present a fiber-compatible FOPO featuring a robust and compact structure, synchronized with a Ti:sapphire laser as the pump source for SRS imaging. It delivers picosecond pulses tunable from 842 to 863 nm with a linewidth of ∼ 1 nm. We also demonstrate SRS imaging of polystyrene and polymethyl methacrylate microbeads at 980 cm − 1 and 1000 cm − 1 , verifying the applicability of this FOPO light source for SRS imaging. This work represents a practical step toward realizing low-noise, fiber-integrated light sources for nonlinear optical imaging.