A stable, rugged, capacitance-stabilised piezoelectric scanned Fabry-Perot etalon

In many spectroscopic and interferometric applications, the plate separation of a Fabry-Perot etalon has to be repeatably stepped or scanned over at least one free spectral range. A convenient technique for adjusting the plate separation of an etalon is by means of piezoelectric transducers which may be stabilised by a capacitance micrometer servo-loop. Several optically-contacted etalons have been constructed where the capacitive elements are integral features of the three spacers which also incorporate the piezoelectric transducers. Due to the optical contacting used throughout the device, the etalon is stable against mechanical shock and vibration for most laboratory and field applications. For space-flight applications, however, the spacers have been bonded using cyanoacrylate adhesives.