Theoretical estimation of stimulated and spontaneous Raman signals in Raman microscopy

As a highly sensitive vibrational imaging method, stimulated Raman scattering (SRS) microscopy is finding various applications, while its theoretical treatment seems still under development. Here we present a theoretical estimation of spontaneous Raman signal and SRS signal from Raman scattering cross section, irrespective of the numerical aperture of the objective lens. We confirm a reasonable agreement between our theory with a recently proposed treatment based on the stimulated Raman scattering cross section. Furthermore, we point out that the acceleration factor of SRS can be interpreted as the number of Stokes photons in the vibrational coherence time.