Frequency shift caused by the line-shape asymmetry of the resonance of coherent population trapping
V. I. Yudin, M. Yu. Basalaev, А. В. Тайченачев, O. N. Prudnikov, Daba Radnatarov, Sergey Kobtsev, S M Ignatovich, M. N. Skvortsov
Abstract
We theoretically study the frequency shift in atomic clocks caused by the line-shape asymmetry of coherent population trapping (CPT) resonance in a bichromatic laser field. This asymmetry arises due to the inequality of the resonant spectral components and nonzero one-photon detuning. The line-shape-asymmetry-induced shift depends on the intensity of the resonant fields, which leads to a degradation in long-term stability due to fluctuations of the laser field parameters. A frequency stabilization based on the harmonic modulation of two-photon detuning is considered. It is shown that the use of a high-frequency modulation (compared to the CPT resonance width, i.e., the Pound-Drever-Hall regime) makes it possible to significantly suppress this shift (by one to two orders of magnitude).