Abstract
Tip enhanced near-field scanning optical microscopy and coherent anti-Stokes Raman scattering (CARS) spec-troscopy, a type of nonlinear Raman spectroscopy, have been successfully combined to image and analyze molecular distribution of nano-structures. Owing to the third order nonlinearity of the CARS process, the excitation of the CARS polarization is extremely confined to the end of the tip apex, resulting in high image contrast and high spatial resolution far beyond the diffraction limit of light. Our tip-enhanced CARS micro-scope visualized a deoxyribonucleic acid (DNA) network structure at a characteristic vibration-frequency (1337cm-1) in the fingerprint region with a spatial resolution of-15nm.
