Visible enhanced stimulated Raman scattering microscopy via frequency-doubling of picosecond pulses

We report visible-enhanced stimulated Raman scattering (VIS-SRS) microscopy by direct frequency-doubling of picosecond pulsed lasers. Compared to previous reports from femtosecond sources, our setup is greatly simplified by removing the need to perform spectral focusing and allows for quick wavelength tuning for sparse multi-channel imaging across a large spectral range. We report a signal enhancement of 3.2-fold for the C–H bond from decane, consistent with theoretical analysis, and up to 483-fold with resonance enhancement. We showcase a multi-channel imaging application in HeLa cells and demonstrate a spatial resolution down to 47 nm from 5xFAD mouse brain tissues coupled with Raman-tailored sample-expansion. Finally, we discuss the future applications and limitations of our picosecond-doubled VIS-SRS.