Nano-Raman Spectroscopy and Imaging with the Near-field Scanning Optical Microscope

We have performed Raman spectroscopy using a near-field scanning optical microscope. This avoids the diffraction limit inherent with conventional optical microscopy techniques involving far-field optical components, and allows volumes significantly smaller than the cube of the wavelength to be investigated. The small sample volume coupled with the light-starved nature of the Raman effect itself makes such nano-Raman studies difficult. We describe a near-field Raman microscope and present results showing near-field effects in an investigation of Rb-doped KTP. A n image taken within a Raman feature demonstrates that nano-Raman imaging is indeed possible if the near-field instrument has considerable longterm stability, and that several unique aspects of the near field data recommend this approach.