What are the advantages and disadvantages of ultra-violet (UV) lasers for Raman?
Ultra-violet (UV) lasers for Raman spectroscopy typically include laser wavelengths ranging from 244 nm through to 364 nm. Theoretically UV Raman spectroscopy is no different from standard analysis using visible laser wavelengths. However, in practice there are a number of practical difficulties and disadvantages which must be considered. Advantages • With certain samples, UV laser excitation can interact in ways not possible when using visible laser sources. For example, in semiconductor materials the penetration depth of UV light is typically in the order of a few nanometers, and thus UV Raman can be used to selectively analyse from a thin top surface layer (as is commonly found in silicon on insulator SOI materials). In another example, UV excitation can give rise to specific resonance enhancement with biological moieties, particularly protein, DNA and RNA structures. Specific analysis of these materials within tissue can be difficult using visible laser wavelengths. • Fluorescence