A spectrometer for high-resolution and high-contrast Brillouin spectroscopy in the ultraviolet

We present a multiple-grating spectrometer designed for high-resolution and high-contrast low-frequency scattering spectroscopy in the ultraviolet, as well as in the visible spectral regions. The instrument has a resolution better than 1 GHz and a contrast of about 1e-10 both in the visible and in the UV range, thus doubling the highest resolution achieved by double-monochromator double-pass spectrometers such as the SOPRA DMDP2000, conceived for Raman-Brillouin spectroscopy using visible excitation. Performance tests and the Brillouin spectra obtained in the ultraviolet range are reported. Ray tracing results, aiming to give a better insight on the instrument performances are also presented. The instrument opens the possibility to study a new region of the exchanged momentum with a suitable energy resolution and to investigate the spectrum of density fluctuations in materials where the UV penetration depth could be a relevant step for the experimental study of the dynamics of disordered material.