Coherent anti-Stokes Raman spectroscopy for nano-imaging with a metallic near-field probe

Abstract

A metallic nano-probe has locally induced coherent anti-Stokes Raman scattering (CARS) of adenine molecules in a nanometric DNA network structure. The excitation fields and CARS polarization are enhanced by the tip apex of the nano-probe through the excitation of local surface plasmons. Owing to the third-order nonlinearity- the excitation of the CARS polarization is extremely confined to the end of the tip apex. resulting in the spatial resolution far beyond the diffraction limit of light. Our CARS microscope using a silver-coated probe visualized the DNA network structure at a specific vibrational frequency (similar to1337 cm(-1)) of adenine molecules with a spatial resolution of similar to15 nm and sufficient sensitivity.