This paper presents Raman and Brillouin scattering measurements obtained with a Fourier transform interferometer, in which the laser light rejection was provided by an alkali-metal vapor cell. The narrow absorption band of the vapor cell allowed for the detection of energy shifts as low as 0.85 cm-1(~26 GHz) while completely blocking scattered light at the laser frequency. Since, unlike a Fabry-Perot interferometer, a Fourier transform interferometer does not have a free spectral range placing an upper bound on the energy shifts which it can detect without ambiguity, the energy regimes of both Brillouin and Raman scattering are for the first time accessible with a single instrument.
P. J. Horoyski and M. L. W. Thewalt, "Fourier Transform Raman and Brillouin Spectroscopy Using Atomic Vapor Filters," Appl. Spectrosc. 48, 843-847 (1994)