Digital control of Fabry-Pérot interferometers

Fabry-Perot interferometry (FPI) originally invented for spectroscopy is now evolving as a basic technology for ultra-fine dimensional stabilization and measurement. To this end, the light path length of an optical cavity and the wavelength of a laser source injected into the cavity have to be each other tuned through a set of frequency and/or displacement actuators driven by a sharp and narrow signal encoding total cavity detuning. Digital control is essential in facilitating and automating the FPI use in view of space applications and routine instrumentation. Embedded model control (EMC) developed by one of the authors has been employed. Experimental results are presented.