Double radio–optical resonance in alkali metal vapors subjected to laser excitation

An investigation was made of a double radio–optical resonance (DROR) in a multilevel system of the alkali metal type. Equations for the density matrix were solved to obtain expressions for the signal, DROR line width, and shift of the maximum of DROR line peak. A study was made of the principal characteristics of a DROR in an optically dense medium in the form of a rubidium vapor. The ultimate short-term frequency instability of a rubidium discriminator was estimated to be 2 X 10 ^{– 14} t ^{– 1/2}. Several experiments were carried out using an injection laser as an optical pump source. The results of the measurements yielded a short-term instability of 3 X 10 ^{– 12} t ^{– 1/2}. An investigation was made of the optical frequency shift and an anomalous dependence of the shift on the intensity was observed. The results of the experimental and theoretical investigations were compared. The requirements for stabilization of the DROR parameters needed to reduce the frequency instability of a rubidium discriminator to the 10 ^{– 14} level were identified.