Collection mode nano-Raman setup

With confocal Raman microscopy, detailed images of the three-dimensional structure of thick samples (such as porous materials, aggregated nanoparticles etc.) could be readily acquired and visualized with sub-micron resolution. However, confocal Raman microscopy is not a panacea, especially for the studies of nanostructures, mainly because of diffraction limits for the optical resolution. The spatial resolution of Raman systems employing traditional optical microscopes is limited to approximately the wavelength of the light (about 0.5 um), because both the illuminating laser light and the Raman scattered light are collected in the optical far-field (i.e. many wavelengths of light away from the scattering material). We will describe a new setup for nano-Raman experiments by using the fiber-optic scanning probe of a Scanning Near Field Optical Microscope (SNOM). The collected Raman signal in this near-field geometry reaches spatial resolutions at the level of tens of nanometers.