Optimization of laser wavelength, power and pulse duration for eye-safe Raman spectroscopy

Raising the interest in remote chemical analysis, in particular through Raman and fluorescence spectroscopy, the opportunity of increasing the exposure represents an important step for an easier and more reliable spectrum analysis. However, the European directive 2006/25/EC defines the maximum permitted exposure (MPE) to artificial radiations according to exposure duration, wavelength, coherence of the radiation and beam divergence. Though the Raman cross section scales in general according to the fourth power of the excitation wavelength, promoting the use of deep UV radiation, a synergy between wavelength and exposure time can raise the Raman signal in the near UV or in the near IR if compliance to eye-safety directives is requested. In this work we will analyze the possibilities offered by commercially available components for enhancing the Raman scattering under eye-safe conditions.