A high-power, broad-area laser diode was used as an incident light source in a Raman spectrometer. The laser was forced to lase in a very narrow frequency range ( 400 MHz) by the use of a Metcalf-Littman arrangement. All side bands and light-emitting diode (LED) modes were suppressed; their intensities are lower than the noise of recorded rotational spectra. The incident wavelength was tuned to coincide with the D1 transition of 85Rb. Due to this choice, the elastically scattered light (Rayleigh component) can be eliminated by a Rb cell in front of the spectrometer. The usefulness of this arrangement is demonstrated for CO2, N2, and air. Because of the suppression of the dominating Rayleigh intensity, this setup is ideally suited for a Fourier transform Raman spectrometer.
R. Claps, J. Sabbaghzadeh, and M. Fink, "Raman Spectroscopy with a Single-Frequency, High-Power, Broad-Area Laser Diode," Appl. Spectrosc. 53, 491-496 (1999)