Description
In Raman Spectroscopy, a specimen is illuminated with laser light and its corresponding spectrum analyzed.  Ground-level vibrational and/or rotational energy changes in molecules caused by inelastic light scattering produce a characteristic molecular "fingerprint".

Raman Spectroscopy systems normally employ a diffraction grating.  There are stringent grating requirements in Raman Spectroscopy because of the extremely weak spectral lines produced very close to the very strong laser illumination wavelengths.  Each scattered photon counts and scattering polarizations are random.  Therefore, high efficiencies in both polarizations along with minimal stray light are necessary and are best provided by volume phase holographic gratings.