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Journal of Optics B Quantum and Semiclassical Optics

Intensity–intensity correlations in a V-type atom driven by a coherent field in a broadband squeezed vacuum

F. Carreño, M. A. Antón, Óscar G. Calderón

Published May 21, 2004• 7 citations
Publisher

Abstract

We study the intensity–intensity correlation in a closely spaced doublet V-type three-level atom driven by an external coherent field and damped by a broadband squeezed vacuum. We are interested in the manner in which the atom emits photons under the combined effect of quantum interference and squeezed vacuum. For distinguishable photons and degenerate transitions, the squeezed field produces anticorrelation, whereas for nondegenerate transitions the effect of the squeezed field is the surpassing of the antibunching during certain time intervals. We find that bunching/antibunching behaviour and the symmetry of the two emission processes can be controlled by the relative phase of the squeezed vacuum to the coherent field. For particular conditions we show a bunching behaviour which turns to antibunching when the two-photon correlations in the squeezed vacuum are reduced to the classical level. Therefore, this transition must be attributed to the quantum nature of the squeezed vacuum. We also study the sideband correlations. We find that squeezed vacuum makes the sidebands evolve at different rates which are phase dependent.

DOI
10.1088/1464-4266/6/7/009

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We investigate the two-time intensity correlation functions of the fluorescence field emitted from a VVV-type three-level atom. We are particularly interested in the manner in which the atom emits photons in the presence of quantum interference. We show that under strong-field excitation quantum interference leads to anticorrelations of photons emitted from the atomic excited levels which can exist for extremely long times. This indicates that the excited atomic levels are not the preferred radiative states. We find that the atom spends most of its time in a superposition of the excited atomic levels from which it emits strongly correlated photons. The strong correlations are present only for a nonzero splitting between the excited levels, and for degenerate levels the correlations reduce to that of a two-level atom. Moreover, we find that the transition from the ground level to the symmetric superposition of the excited levels does not saturate even for a strong driving field. We also calculate the correlation functions for a weak driving field, and find that in this case the photon correlations are not significantly affected by quantum interference, but the atom can emit a strongly correlated pair of photons produced by a three-wave mixing process. Under appropriate conditions, with near-maximal quantum interference, it is possible to make the maximum value of the correlation function extremely large, in marked contrast with the corresponding case with no quantum interference.
Phase-dependent squeezing spectrum and photon antibunching of resonance fluorescence from a three-level V-type atom driven by a coherent field are investigated. We show that for weak excitation intensities quantum interference can greatly enhance squeezing and change the phase quadrature at which the maximum squeezing occurs. We also notice that the maximum squeezing can appear not only in either the in-phase or the out-of-phase quadrature but also in any phase quadrature, and at which phase quadrature the maximum squeezing display can be controlled by choosing the detuning of the driving field from the atomic transition. However, quantum interference can't enhance antibunching effect greatly.
two-mode squeezed vacuum field interacting with a V-type three-level moving atom is investigated. We can get analytic expressions of second-order correlation function and two-mode correlation function. The influence of atomic motion, the field structure and intensity of photons on second-order correlation function and two-mode correlation function are obtained by numerical calculation. The results indicate that correlation function and photon bunching increase obviously when intensity of photons increase; photon bunching and antibunching don't change when atomic motion and the field structure increase, but the period of photon bunching and antibunching reduce greatly.
In this paper we analyze the steady-state populations and gain lineshape of a V-type three-level atom with a closely spaced excited doublet. The atom is driven by a strong coherent field, a weak probe, and a single broadband squeezed vacuum. We focus our attention in the interplay between the quantum interference and the squeezed field on the probe gain. It is shown that the relative phases between the two coherent fields and the squeezed field play an important role in the optical properties of the atom. Specifically, we find that the probe can experience gain without population inversion for proper values of the parameters characterizing the squeezed field and in the absence of incoherent pumping. The system can be tailored to exhibit multiple dispersion regimes accompanied by negligible gain or absorption over a large bandwidth, a desirable feature for obtaining propagation of pulses with negligible distortion.
We study fluorescence from a three-level atom in a cascade configuration driven by two coherent fields and damped by a broadband squeezed vacuum. Under the conditions that one or both of these fields are intense, a secular approximation is invoked to derive an analytical solution of the relevant master equation. When the two fields are in exact resonance with their respective transitions, expressions for the fluorescent spectra show a narrowing of the central peak for some specific values of the parameters of the squeezed vacuum and the phases between the driving fields and the squeezed vacuum. We also present analytical expressions for second-order intensity correlations. The inhibition of fluorescence in a squeezed vacuum is reflected in the quantum-jump-like behavior shown by these correlations.
A single two-level atom in a coherently driven cavity and damped by a broadband squeezed vacuum centered about the atomic transition frequency is studied. A second-order Fokker-Planck equation for this system is obtained without using system size expansion. Effects of detunings and cavity decays are also incorporated in the Fokker-Planck equation. This equation is used to study atomic inversion, fluorescent spectrum, and the intensity correlations of the transmitted and fluorescent photons in the bad-cavity limit. Several interesting effects in the atomic inversion, spectrum, and intensity correlations due to the squeezed vacuum are presented. These results are also compared with an atom that is damped by a thermal reservoir.