Eur. Phys. J. D 19, 411-419 (2002)
https://doi.org/10.1140/epjd/e20020079

Absorption and dispersion by a multiple driven two-level atom

¹ Institut für Theoretische Physik, Technische Universität Wien, Wiedner Hauptstrasse 8-10/136, 1040 Wien, Austria
² Department of Physics and Centre for Laser Science, The University of Queensland, Brisbane, QLD 4072, Australia
³ Department of Statistical Mechanics, V.A. Steklov Mathematical Institute, GSP-1, 117966, Gubkin Street 8, Moscow, Russia

Corresponding author: ^a ficek@physics.uq.edu.au

Received: 23 October 2001
Revised: 31 January 2002
Published online: 15 June 2002

Abstract

We investigate the absorption and dispersion properties of a two-level atom driven by a polychromatic field. The driving field is composed of a strong resonant (carrier) frequency component and a large number of symmetrically detuned sideband fields (modulators). A rapid increase in the absorption at the central frequency and the collapse of the response of the system from multiple frequencies to a single frequency are predicted to occur when the Rabi frequency of the modulating fields is equal to the Rabi frequency of the carrier field. These are manifestations of the undressing or a disentanglement of the atomic and driving field states, that leads to a collapse of the atom to its ground state. Our calculation permits consideration of the question of the undressing of the driven atom by a multiple-modulated field and the predicted spectra offer a method of observing undressing. Moreover, we find that the absorption and dispersion spectra split into multiplets whose structures depend on the Rabi frequency of the modulating fields. The spectral features can jump between different resonance frequencies by changing the Rabi frequency of the modulating fields or their initial phases, which can have potential applications as a quantum frequency filter.