Computer-controlled Fabry-Perot interferometer for Brillouin spectroscopy

Long measuring times are required to obtain an adequate SNR when recording weak intensity scattered light spectra with a Fabry-Perot interferometer. Drifts of laser frequency and mechanical and thermal instabilities of the interferometer, which affect the exact adjustment of the Fabry-Perot plates, are disturbing factors in the measurement. The system described here consists of a piezoelectrically scanned Fabry-Perot interferometer and a computer-controlled multichannel analyzer which uses the elastically scattered line (Rayleigh line) as a reference in order to compensate drifts of laser frequency and allow parallel alignment of the mirrors over long periods of time.