Simple pressure-tuned Fabry-Perot interferometer

A simple, compact and inexpensive pressure-tuned Fabry-Perot interferometer is presented. It is used as a laser locking reference for optical frequencies where the use of an atomic reference is impractical. The scanning range is several GHz. Absolute positioning of the interferometer with an accuracy of 7 MHz rms over a range of 2 GHz is possible. The instrument is temperature stabilized and shows long-term drift of 16 MHz rms over 48 h. (C) 2005 American Institute of Physics.