Triple-frequency symmetric subtraction scheme for nonresonant background suppression in coherent anti-Stokes Raman scattering (CARS) microscopy.

We report a unique triple-frequency symmetric subtraction scheme to effectively remove the nonresonant background in coherent anti-Stokes Raman scattering (CARS) microscopy. Theoretical and experimental studies show that this unique scheme has an optimal performance for high contrast vibrational imaging, particularly useful when the resonant signal was larger than or comparable to the nonresonant background.