46 research outputs found
Nonlinear optics via double dark resonances
Double dark resonances originate from a coherent perturbation of a system
displaying electromagnetically induced transparency. We experimentally show and
theoretically confirm that this leads to the possibility of extremely sharp
resonances prevailing even in the presence of considerable Doppler broadening.
A gas of 87Rb atoms is subjected to a strong drive laser and a weak probe laser
and a radio frequency field, where the magnetic coupling between the Zeeman
levels leads to nonlinear generation of a comb of sidebands.Comment: 6 pages, 9 figure
Ultrahigh sensitivity of slow-light gyroscope
Slow light generated by Electromagnetically Induced Transparency is extremely
susceptible with respect to Doppler detuning. Consequently, slow-light
gyroscopes should have ultrahigh sensitivity
Laser induced breakdown of the magnetic field reversal symmetry in the propagation of unpolarized light
We show how a medium, under the influece of a coherent control field which is
resonant or close to resonance to an appropriate atomic transition, can lead to
very strong asymmetries in the propagation of unpolarized light when the
direction of the magnetic field is reversed. We show how EIT can be used to
mimic effects occuring in natural systems and that EIT can produce very large
asymmetries as we use electric dipole allowed transitions. Using density matrix
calculations we present results for the breakdown of the magnetic field
reversal symmetry for two different atomic configurations.Comment: RevTex, 6 pages, 10 figures, Two Column format, submitted to Phys.
Rev.
Temperature Variation of Ultra Slow Light in a Cold Gas
A model is developed to explain the temperature dependence of the group
velocity as observed in the experiments of Hau et al (Nature {\bf397}, 594
(1999)). The group velocity is quite sensitive to the change in the spatial
density. The inhomogeneity in the density and its temperature dependence are
primarily responsible for the observed behavior.Comment: 12 pages, 4 figure
From Storage and Retrieval of Pulses to Adiabatons
We investigate whether it is possible to store and retrieve the intense probe
pulse from a -type homogeneous medium of cold atoms. Through numerical
simulations we show that it is possible to store and retrieve the probe pulse
which are not necessarily weak. As the intensity of the probe pulse increases,
the retrieved pulse remains a replica of the original pulse, however there is
overall broadening and loss of the intensity. These effects can be understood
in terms of the dependence of absorption on the intensity of the probe. We
include the dynamics of the control field, which becomes especially important
as the intensity of the probe pulse increases. We use the theory of adiabatons
[Grobe {\it et al.} Phys. Rev. Lett. {\bf 73}, 3183 (1994)] to understand the
storage and retrieval of light pulses at moderate powers.Comment: 15 pages, 7 figures, typed in RevTe
Temporal build-up of electromagnetically induced transparency and absorption resonances in degenerate two-level transitions
The temporal evolution of electromagnetically induced transparency (EIT) and
absorption (EIA) coherence resonances in pump-probe spectroscopy of degenerate
two-level atomic transition is studied for light intensities below saturation.
Analytical expression for the transient absorption spectra are given for simple
model systems and a model for the calculation of the time dependent response of
realistic atomic transitions, where the Zeeman degeneracy is fully accounted
for, is presented. EIT and EIA resonances have a similar (opposite sign) time
dependent lineshape, however, the EIA evolution is slower and thus narrower
lines are observed for long interaction time. Qualitative agreement with the
theoretical predictions is obtained for the transient probe absorption on the
line in an atomic beam experiment.Comment: 10 pages, 9 figures. Submitted to Phys. Rev.
Phase Coherence and Control of Stored Photonic Information
We report the demonstration of phase coherence and control for the recently
developed "light storage" technique. Specifically, we use a pulsed magnetic
field to vary the phase of atomic spin excitations which result from the
deceleration and storing of a light pulse in warm Rb vapor. We then convert the
spin excitations back into light and detect the resultant phase shift in an
optical interferometric measurement. The coherent storage of photon states in
matter is essential for the practical realization of many basic concepts in
quantum information processing.Comment: 5 pages, 3 figures. Submitted to Phys. Rev. Let
Slow Light in Doppler Broadened Two level Systems
We show that the propagation of light in a Doppler broadened medium can be
slowed down considerably eventhough such medium exhibits very flat dispersion.
The slowing down is achieved by the application of a saturating counter
propagating beam that produces a hole in the inhomogeneous line shape. In
atomic vapors, we calculate group indices of the order of 10^3. The
calculations include all coherence effects.Comment: 6 pages, 5 figure
A Knob for Changing Light Propagation from Subluminal to Superluminal
We show how the application of a coupling field connecting the two lower
metastable states of a lambda-system can produce a variety of new results on
the propagation of a weak electromagnetic pulse. In principle the light
propagation can be changed from subluminal to superluminal. The negative group
index results from the regions of anomalous dispersion and gain in
susceptibility.Comment: 6 pages,5 figures, typed in RevTeX, accepted in Phys. Rev.
Coupled cavities for enhancing the cross-phase modulation in electromagnetically induced transparency
We propose an optical double-cavity resonator whose response to a signal is
similar to that of an Electromagnetically Induced Transparency (EIT) medium. A
combination of such a device with a four-level EIT medium can serve for
achieving large cross-Kerr modulation of a probe field by a signal field. This
would offer the possibility of building a quantum logic gate based on photonic
qubits. We discuss the technical requirements that are necessary for realizing
a probe-photon phase shift of Pi caused by a single-photon signal. The main
difficulty is the requirement of an ultra-low reflectivity beamsplitter and to
operate a sufficiently dense cool EIT medium in a cavity.Comment: 10 pages, 5 figures, REVTeX, to appear in Phys. Rev. A (v2 - minor
changes in discussion of experimental conditions