J. Zaremba

Electromagnetically induced transparency and storing of a pair of pulses of light

Electromagnetically induced transparency and light storing are discussed in the case of an atomic medium in a double {lambda} configuration. A polariton description of both phenomena is systematically introduced. Analytic expressions are given which allow one to predict the shapes and phases of both the transmitted pulses and the stored and released ones as well as the atomic coherence in the storage stage. A comparison of the numerical solutions of the Maxwell-Bloch equations with the results due to the polariton model proves a strong predictive power of the latter.

Beam splitting and Hong-Ou-Mandel interference for stored light

Storing and release of a quantum light pulse in a medium of atoms in the tripod configuration are studied. Each of these operations is realized by switching on and off two sets of properly chosen control fields. The system constitutes a kind of a flexible beam splitter in which the input and output ports concern photons of the same direction but well separated in time. A version of Hong-Ou-Mandel interference is discussed. It is also shown that a stored nonclassical light is split into two nonclassical beams, with their statistical properties being steered by a choice of the control fields.

Controlled light storage in a double lambda system

It is shown theoretically that after light storing in a medium of four-level atoms it is possible to release a new pulse of a different frequency, the process being steered by another driving beam. It is also possible to store one pulse and to release two different ones, with their time separation and heights being controlled. The problem of adiabaticity of the evolution is discussed in terms of dark and bright state polaritons.

Electromagnetically induced transparency and light slowdown for Λ-like systems with a structured continuum

Abstract Electric susceptibility of a laser-dressed atomic medium is calculated for a model Λ-like system including two lower states and a continuum structured by a presence of an autoionizing state or a continuum with a laser-induced structure. Depending on the strength of a control field, it is possible to obtain a significant reduction of the light velocity in a narrow frequency window in the conditions of a small absorption. It is shown that increasing the values of the asymmetry parameters leads to an increase of the values of both real and imaginary parts of the medium susceptibility and to an increase of the width of the transparency window, compared with the case of a flat continuum. A smooth transition is shown between the case of a flat continuum and that of a discrete state serving as the upper state of a Λ system.

Tunable photonic metamaterials

We illustrate a mechanism based on coherent optical nonlinearities to realize optically tunable photonic crystals built from media supporting electromagnetically induced transparency. These exhibit specific periodic patterns where a light probe can experience a fully developed photonic band-gap with negligible absorption. An analytical method based on a two-mode approximation is developed to study the optical response of such a periodically modulated medium driven into a regime of standing-wave electromagnetically induced transparency. A comparison with a transfer matrix approach and with techniques based on the coupled Maxwell–Liouville equations shows that our method is very accurate to describe the optical properties of such photonic metamaterials in the frequency region of interest. Nearly perfect reflectivities may be attained for ultracold 87Rb atoms samples which are seen to reflect with little loss and deformation light pulses whose frequency components are contained within the gap. When the same mechanism is implemented for inhomogeneously broadened optical transitions of nitrogen-vacancy centers in diamond, which is more amenable to device applications, fully developed photonic band-gap structures with negligible absorption, reflectivities very close to unity and sufficiently large bandwidths may also be attained. We further examine more flexible schemes based on four level systems under double driving conditions showing more accurate and efficient coherent optical control of the photonic band-gap. The remarkable experimental simplicity of the schemes that we presented is set to ease quantum nonlinear optics applications.

Pulse propagation in atomic media in the triangular configuration

Weak probe-pulse propagation is studied in a three-level atomic system irradiated by a strong control laser field and a strong microwave field in the closed-loop triangular (Δ) configuration. In addition to the direct absorption channel, a second channel is activated in which a probe photon’s absorption is replaced by its emission accompanied by an absorption of two control and two microwave photons. The pulse can be considered a superposition of two components, each of which experiences a separated effective susceptibility, exhibiting its absorption/gain windows. The evolution of the pulse spectrum in space and the pulse evolution in space–time are discussed. In particular it is shown that the number and positions of the spectrum peaks change and the pulse exhibits beats. In addition to the propagating field, a stationary light generated by the sample is also discussed.

Coherent processing of a light pulse stored in a medium of four-level atoms

It is demonstrated that the properties of light stored in a four-level atomic system can be modified by an additional control interaction present during the storage stage. By choosing the pulse area of this interaction one can in particular continuously switch between two channels into which light is released.

Threshold effects in photoionization and photodetachment

Abstract The subject of near-threshold strong-field photoionization and photodetachment is reviewed and presented in a uniform and systematic way. The general formalism of the resolvent is applied to predict and explain theoretically the particular threshold effects like, in the simplest case, a nonexponential decay of the initial state population and non-Lorentzian photoelectron spectra. A smooth transition from the situation of the laser being tuned deep below the continuum edge, with the resulting population trapping, to the usual case of a photoionization and photodetachment high above the threshold is demonstrated, both for atomic systems and for negative ions. Various particular examples of photoionization and photodetachment are reviewed and the general theoretical conclusion are illustrated by numerical model calculations.

Pulse propagation in a medium optically dressed by three fields forming a triangular loop configuration

A probe pulse propagation is examined in a medium irradiated by three control fields which constitute a triangular loop system being, in general, out of resonance. As a consequence, the probe field interacts with the medium dressed in a time-dependent way. Coupled equations for the Floquet components of the probe field are written and solved by diagonalizing the coupling matrix. Examples of numerical solutions are presented and discussed.

Cross-Kerr nonlinearities in an optically dressed periodic medium

Cross-Kerr nonlinearities are analyzed for two light beams propagating in an atomic medium in the tripod configuration, dressed by a strong standing-wave laser field that induces periodic optical properties. The reflection and transmission spectra as well as the phases of both the reflected and transmitted components of the two beams are analyzed theoretically with nonlinearities up to third order being taken into account. Ranges of parameters are sought in which the cross-Kerr effect can be used as the basis of the phase gate.