114 research outputs found
Bistability in Feshbach Resonance
A coupled atom-molecule condensate with an intraspecies Feshbach resonance is
employed to explore matter wave bistability both in the presence and in the
absence of a unidirectional optical ring cavity. In particular, a set of
conditions are derived that allow the threshold for bistability, due both to
two-body s-wave scatterings and to cavity-mediated two-body interactions, to be
determined analytically. The latter bistability is found to support, not only
transitions between a mixed (atom-molecule) state and a pure molecular state as
in the former bistability, but also transitions between two distinct mixed
states.Comment: 6 pages + 3 figures; To appear in Jounal of Modern Optics, Special
Issue - Festschrift in Honor of Lorenzo Narducc
Coupled-resonator-induced reflection in photonic-crystal waveguide structures
We study the resonant transmission of light in a coupled-resonator optical
waveguide interacting with two nearly identical side cavities. We reveal and
describe a novel effect of the coupled-resonator-induced reflection (CRIR)
characterized by a very high and easily tunable quality factor of the
reflection line, for the case of the inter-site coupling between the cavities
and the waveguide. This effect differs sharply from the
coupled-resonator-induced transparency (CRIT) -- an all-optical analogue of the
electromagnetically-induced transparency -- which has recently been studied
theoretically and observed experimentally for the structures based on
micro-ring resonators and photonic crystal cavities. Both CRIR and CRIT effects
have the same physical origin which can be attributed to the Fano-Feshbach
resonances in the systems exhibiting more than one resonance. We discuss the
applicability of the novel CRIR effect to the control of the slow-light
propagation and low-threshold all-optical switching.Comment: LaTeX, 11 pages, 5 figure
Matter-wave bistability in coupled atom-molecule quantum gases
We study the matter-wave bistability in coupled atom-molecule quantum gases,
in which heteronuclear molecules are created via an interspecies Feshbach
resonance involving either two-species Bose or two-species Fermi atoms at zero
temperature. We show that the resonant two-channel Bose model is equivalent to
the nondegenerate parametric down-conversion in quantum optics, while the
corresponding Fermi model can be mapped to a quantum optics model that
describes a single-mode laser field interacting with an ensemble of
inhomogeneously broadened two-level atoms. Using these analogy and the fact
that both models are subject to the Kerr nonlinearity due to the two-body
s-wave collisions, we show that under proper conditions, the population in the
molecular state in both models can be made to change with the Feshbach detuning
in a bistable fashion.Comment: 6 pages, 5 figure
Bifurcations and bistability in cavity assisted photoassociation of Bose-Einstein condensed molecules
We study the photo-association of Bose-Einstein condensed atoms into
molecules using an optical cavity field. The driven cavity field introduces a
new dynamical degree of freedom into the photoassociation process, whose role
in determining the stationary behavior has not previously been considered. The
semiclassical stationary solutions for the atom and molecules as well as the
intracavity field are found and their stability and scaling properties are
determined in terms of experimentally controllable parameters including driving
amplitude of the cavity and the nonlinear interactions between atoms and
molecules. For weak cavity driving, we find a bifurcation in the atom and
molecule number occurs that signals a transition from a stable steady state to
nonlinear Rabi oscillations. For a strongly driven cavity, there exists
bistability in the atom and molecule number
Fano resonances in nanoscale structures
Nowadays nanotechnology allows to scale-down various important devices
(sensors, chips, fibres, etc), and, thus, opens up new horizon for their
applications. Nevertheless, the efficiency most of them is still based on the
fundamental physical phenomena, such as resonances. Thus, the understanding of
the resonance phenomena will be beneficial. One of the well-known examples is
the resonant enhancement of the transmission known as Breit-Wigner resonances,
which can be described by a Lorentzian function. But, in many physical systems
the scattering of waves involves propagation along different paths, and, as a
consequence, results in interference phenomena, where constructive interference
corresponds to resonant enhancement and destructive interference to resonant
suppression of the transmission. Recently, a variety of experimental and
theoretical work has revealed such patterns in different branches of physics.
The purpose of this Review is to demonstrate that this kind of resonant
scattering is related to the Fano resonances, known from atomic physics. One of
the main features of the Fano resonances is the asymmetric profile. The
asymmetry comes from the close coexistence of resonant transmission and
resonant reflection. Fano successfully explained such a phenomenon in his
seminal paper in 1961 in terms of interaction of a discrete (localized) state
with a continuum of propagation modes. It allows to describe both resonant
enhancement and resonant suppression in a unified manner. All of these
properties can be demonstrated in the frame of a very simple model, which will
be used throughout the Review to show that resonant reflections observed in
different complex systems are indeed closely related to the Fano resonances.Comment: This review paper was submitted to Review of Modern Physics. But all
comments are still welcome
Polariton interactions in semiconductor microcavities
In this review, we will try to summarize the results that we have obtained on the measurement of polariton interactions. We will describe here the samples, the experimental systems and some of the important results. We will also give a few highlights on the theoretical description of these results. One of the main topics of this review will be the observation of the Feshbach resonance for polaritons, and its interpretation through the coupling of two lower polaritons into a biexciton. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved
Backaction-Driven Transport of Bloch Oscillating Atoms in Ring Cavities
We predict that an atomic Bose-Einstein condensate strongly coupled to an
intracavity optical lattice can undergo resonant tunneling and directed
transport when a constant and uniform bias force is applied. The bias force
induces Bloch oscillations, causing amplitude and phase modulation of the
lattice which resonantly modifies the site-to-site tunneling. For the right
choice of parameters a net atomic current is generated. The transport velocity
can be oriented oppositely to the bias force, with its amplitude and direction
controlled by the detuning between the pump laser and the cavity. The transport
can also be enhanced through imbalanced pumping of the two counter-propagating
running wave cavity modes. Our results add to the cold atoms quantum simulation
toolbox, with implications for quantum sensing and metrology.Comment: Published version: 5 pages, 4 figures; Supplementary Material
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