A cooled Fabry-Pérot etalon has been constructed for which the parallelism and mirror spacing can be servo-controlled and tuned using an existing commercially available etalon control system. Capacitance sensors monitor the mirror spacing and parallelism, and error signals produced as a consequence of changes in these values are used to stabilize the cavity with piezoelectric actuators. The etalon operates at liquid nitrogen temperature, has a free aperture of 50 mm and a nominal mirror spacing of 60 μm, and is coated for the 3- to 5-μm spectral region. Under servo-control at operating temperature, the response time of the etalon is 30 ms and the cavity tuning range is 6 μm, corresponding to ~ 3 orders of interference at the midrange wavelength of 4 μm.
Newrick K. Reay,
Krzysztof A.R.B. Pietraszewski,
"Liquid-nitrogen-cooled servo-stabilized Fabry-Pérot interferometer for the infrared," Optical Engineering 31(8), (1 August 1992). http://dx.doi.org/10.1117/12.58705