Operator model for frequency modulation of radiation in the optical range

Frequency modulation is achieved in the optical range by changing the length of Fabry-Perot interferometer. Either the geometric dimensions of the interferometer or its optical path length can be changed. The optical path length of the interferometer can be controlled by changing the refractive index of an electrooptical crystal in the cavity.Translated from Izvestiya VUZ. Fizika, No. 5, pp. 35–39, May, 1971.