Recent Developments in Confocal Raman Microprobing and Imaging Techniques

Abstract

This communication presents a summary of the most recent developments in microRaman instrumentation - point analysis and imaging techniques- including the use of confocal optics and line illumination, as now available in certain commercial instruments.The major development in micro-Raman spectroscopic instrumentation during the last few years is based on the extension of the principles of confocal microscopy. Applied to Raman microprobing the confocal technique provides an efficient way to obtain interference-free Raman spectra, as well as two-or three-dimensional, selective images of small specimens embedded within strong scatterers or fluorescent transparent media. As it is well known, the confocal configuration benefits from the use of spatial filtering by optically conjugated pinhole diaphragms. Such a system isolates the light originating from a small region of the sample coincident with the diffraction-limited, focused laser spot, and efficiently eliminates the contributions from out-of-focus zones.A new concept of Raman imaging that benefits from the advantages of confocal microscopy has been developed in this laboratory.