Saturated Raman scattering for sub-diffraction-limited imaging.

We present a scheme for a sub-diffraction-limited Raman microscope. The scheme combines the concept from stimulated depletion microscopy with femtosecond stimulated Raman scattering. The suppression of the Raman signal in a three-beam setup with only two involved wavelength-components was accomplished by the saturation of the Raman scattering. A reduction of the Raman signal of up to 79% could be measured with only a single Raman resonance involved. Based on this signal suppression, a resolution enhancement by a factor of 2 could be verified in a first proof-of-concept measurement, opening up a pathway toward label-free sub-diffraction-limited imaging.