Nonlinear optical indication in frequency-stabilization systems

A theoretical investigation is presented of double resonance in a cell with alkali-metal vapors situated inside a laser resonator. Equations are solved for the density matrix of an atomic vapor subjected to the simultaneous effects of an RF field and a standing optical wave. The parameters of a nonlinear optical indication signal in conditions of double resonance are calculated with allowance for various physical factors. It is noted that the optical indication technique can be used to stabilize quartz oscillators according to the frequency of a reference transition in alkali-metal vapor.