New automatic system for multipass Fabry-Pérot alignment and stabilization

We present a new automatic system for Brillouin scattering experiments employing a double pass Fabry-Pérot interferometer. The main characteristics of the system are a new procedure for reaching and maintaining mirror parallelism over time and the complete automation of most of the tasks involved in a successful Brillouin scattering experiment. The system makes use of a personal computer, a commercially available nanopositioning system with proportional-integral-derivative feedback control capability, and few commercial computer interfaces. The proposed mirror alignment method can be easily adapted to different multipass Fabry-Pérots and turned out to be reliable and practical in common experimental condition. The system does not need thermal stabilization of the surrounding environment and requires human intervention only when changing the free spectral range of the interferometer and/or scattering angle. The results from some tests under different experimental conditions are also reported.