title: Raman microscopy based on doubly-resonant four-wave mixing (DR-FWM).
abstract: Doubly-resonant four-wave mixing (DR-FWM) is a nondegenerate four-wave mixing process in which four photons interact to coherently probe two distinct Raman resonances. We demonstrate DR-FWM microscopy as a label-free and nondestructive molecular imaging modality with high chemical specificity on the submicron scale by imaging alkyne-substituted oleic acid in both aqueous and lipid-rich environments. DR-FWM microscopy is contrasted to coherent anti-Stokes Raman scattering (CARS) microscopy and it is shown that the coherent addition of two simultaneously probed Raman resonances leads to a significant increase in signal without increasing the non-resonant background. Thus, this scheme enables the detection of weak Raman signals through amplification by a strong Raman resonance, potentially increasing the overall detection sensitivity beyond what has been demonstrated by either CARS or stimulated Raman scattering (SRS).
authors.affiliation: NSF Center for Biophotonics Science and Technology, University of California, Davis, Sacramento, CA 95817, USA.
authors.forename: Tyler
authors.initials: T
authors.lastname: Weeks
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wachsmann-Hogiu
authors.forename: Thomas
authors.initials: T
authors.lastname: Huser
mesh_terms: D008853:Microscopy / Q000379:methods*; D019301:Oleic Acid / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013816:Thermodynamics
chemical_list: D019301:Oleic Acid