High Sensitivity Stimulated Raman Scattering Microscopy with Electronic Resonance Enhancement

Raman microscopy is an important tool for labelfree microscopy. However, spontaneous Raman microscopy suffers from slow image acquisition rates and susceptibility to fluorescence background. Coherent Raman microsocopy techniques such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy, by contrast, offer fast imaging capability and robustness against sample fluorescence. Yet, their rather low sensitivity impedes their broader application. This review discusses sensitivity enhancement of SRS microscopy to mu M detection levels by using electronically preresonant excitation. We present the foundations of this approach, discuss its technological implementation, and show first successful applications. A special emphasis is given to outlining new experimental developments allowing novel types of investigations.