Scanning Near-Field Optical Microscopy and Related Techniques

It is often desirable in imaging or spectroscopy to reduce the volume in which incident light irradiates a sample. The aim may be to improve the spatial resolution of a technique, to selectively probe a specific location, or to detect single molecules. One way of achieving this is to use near field optics. This refers to the behavior of light propagating near to a surface, rather than light that is propagating through a medium (as in the more familiar far field optics). Near field optics permits the selective excitation of fluorescence or the high-resolution enhancement of Raman microscopy, beyond the resolution limits that affect conventional optics.