Theory of coherent population trapping resonances for alkali vapors in a buffer-gas cell: 2001 - 2023

by Prof. Alexey Taichenachev

Novosibirsk State University and Institute for Laser Physics

at Quantum optics seminar

Wed, 14 Feb 2024, 16:00
Zoom Only

Abstract

Zoom link: https://us02web.zoom.us/j/82261598260?pwd=QWJ1VnFaME80QkN1dTQzSUdHRkR0QT09

Abstract:
The talk will provide an overview of the results on the theory of coherent population trapping (CPT) resonances for alkali metal vapors in cells with a buffer gas, obtained by the authors in the period 2001 – 2023. The results are based on a simplified theoretical model proposed by the authors in 2001, in which, in the limit of small saturation of the optical transition (D1 or D2 line of alkali metal atoms) and complete collisional depolarization of the excited state, the dynamics of atoms in a polarized frequency-modulated (modulation frequency usually varies near half the frequency of hyperfine splitting in the ground state \Omega ~ \Delta/2 or \Omega ~ \Delta) the laser field is described by a closed quantum kinetic equation for the density matrix of the ground state with a minimum set of relaxation constants. This approach makes it possible to adequately take into account the real structure of atomic energy levels (hyperfine and Zeeman sublevels), as well as the polarization of the frequency components of the field exciting the CPT resonance. A stationary solution of this equation can be found in analytical form [1]. However, in the practical implementation of a quantum frequency standard (QSF) based on CPT resonances (see, for instance, [2]), in order to lock the frequency of the standard \Omega to the splitting frequency of the ground state \Delta, a relatively slow (on the order of kHz) frequency modulation Ω(t) = Ω(0)+A sin(f t), is used which allows you to generate an error signal (or discriminator) during synchronous detection. In the general case, a steady-state periodic solution of the quantum kinetic equation can be found using one or another numerical method (see, for example, [3]). Analytical results can only be obtained in various limiting cases. We considered the following: (1) weak laser field (approximation of the first nonlinear corrections); (2) slow modulations; (3) weak modulations and (4) fast modulations. As an example of practical importance for the development and creation of QSF-CPT, we studied the dependence of the resonance parameters (error signal) on the ellipticity parameter of the polarization of the frequency-modulated laser field.
This work was supported by Russian Science Foundation 23-12-00195.

[1] A.V. Taichenachev, V.I. Yudin, R. Wynands, M. Stahler, J. Kitching, L. Hollberg, Phys. Rev. A 67 033810 (2003).
[2] M.N. Skvortsov et al., Quantum Electronics 50 576 (2020).
[3] V.I. Yudin, A.V. Taichenachev, M.Yu. Basalaev, Phys. Rev. A 93 013820 (2016); V.I. Yudin, M.Yu. Basalaev, A.V. Taichenachev et al., Phys. Rev. A 108 013103 (2023).

Created on 11-02-2024 by Folman, Ron (folman)
Updaded on 11-02-2024 by Folman, Ron (folman)