Nano-Raman Spectroscopy and Imaging with a Near-Field Scanning Optical Microscope

Raman spectroscopy was performed using a near-field scanning optical microscope. This avoids the diffraction limit inherent in 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. A near-field Raman microscope is described and results showing near-field effects in an investigation of Rb-doped KTP are presented. An image taken within a Raman feature demonstrates that nano-Raman imaging is indeed possible if the near-field instrument has considerable long-term stability, and that several unique aspects of the near-field data recommend this approach.