80 research outputs found
Phase control of electromagnetically induced transparency and its applications to tunable group velocity and atom localization
We show that, by simple modifications of the usual three-level -type
scheme used for obtaining electromagnetically induced transparency (EIT), phase
dependence in the response of the atomic medium to a weak probe field can be
introduced. This gives rise to phase dependent susceptibility. By properly
controlling phase and amplitudes of the drive fields we obtain variety of
interesting effects. On one hand we obtain phase control of the group velocity
of a probe field passing through medium to the extent that continuous tuning of
the group velocity from subluminal to superluminal and back is possible. While
on the other hand, by choosing one of the drive fields to be a standing wave
field inside a cavity, we obtain sub-wavelength localization of moving atoms
passing through the cavity field.Comment: To Appear in SPIE Proceedings Volume 573
Subwavelength atom localization via amplitude and phase control of the absorption spectrum
We propose a scheme for subwavelength localization of an atom conditioned
upon the absorption of a weak probe field at a particular frequency.
Manipulating atom-field interaction on a certain transition by applying drive
fields on nearby coupled transitions leads to interesting effects in the
absorption spectrum of the weak probe field. We exploit this fact and employ a
four-level system with three driving fields and a weak probe field, where one
of the drive fields is a standing-wave field of a cavity. We show that the
position of an atom along this standing wave is determined when probe field
absorption is measured. We find that absorption of the weak probe field at a
certain frequency leads to subwavelength localization of the atom in either of
the two half-wavelength regions of the cavity field by appropriate choice of
the system parameters. We term this result as sub-half-wavelength localization
to contrast it with the usual atom localization result of four peaks spread
over one wavelength of the standing wave. We observe two localization peaks in
either of the two half-wavelength regions along the cavity axis.Comment: Accepted for publication to Physical Review
Proposal for a 1 � 3 Goos-H�nchen shift-assisted de/multiplexer based on a multilayer structure containing quantum dots
A multilayer structure with the wavelength selective features based on Goos-H�nchen (GH) shift is proposed and investigated. We present a layered media containing quantum dots for active control of the GH shift for the reflected light. This configuration includes a distributed Bragg reflector to have minimum optical power transmission to the substrate. In addition, a passive cladding layer is used to enhance the total lateral shift for the reflected beams. For a fixed structure and incident angle, our results demonstrate that by proper manipulation of the optical properties and susceptibility of the active layer, de/multiplexing capabilities of such a device could be controlled. This type of grating-less device can be used as a compact wavelength division multiplexing system with actively controllable channel spacing. We demonstrate possibility of a 1 � 3 de/multiplexer with channel spacing of 2 nm. � 2016 Author(s)
Tunable phase control for subluminal to superluminal light propagation
Journals published by the American Physical Society can be found at http://publish.aps.org/We demonstrate tunable control of the group velocity of a weak probe pulse from subluminal to superluminal. The model is an extended Lambda-type system with two extra control fields and an extra energy level. Phase variation of one of the control fields imparts the tunability in the group velocity along with other interesting spectral behavior in the absorption spectrum
Group velocity control in the ultraviolet domain via interacting dark-state resonances
The propagation of a weak probe field in a laser-driven four-level atomic
system is investigated. We choose mercury as our model system, where the probe
transition is in the ultraviolet region. A high-resolution peak appears in the
optical spectra due to the presence of interacting dark resonances. We show
that this narrow peak leads to superluminal light propagation with strong
absorption, and thus by itself is only of limited interest. But if in addition
a weak incoherent pump field is applied to the probe transition, then the peak
structure can be changed such that both sub- and superluminal light propagation
or a negative group velocity can be achieved without absorption, controlled by
the incoherent pumping strength
Prevalence of atherosclerosis and association with 5-year outcome: The Norwegian Stroke in the Young Study
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Controlling laser spectra in a phaseonium photonic crystal using maser
We study the control of quantum resonances in photonic crystals with
electromagnetically induced transparency driven by microwave field. In addition
to the control laser, the intensity and phase of the maser can alter the
transmission and reflection spectra in interesting ways, producing hyperfine
resonances through the combined effects of multiple scattering in the
superstructure.Comment: 7 pages, 4 figure
Gain-assisted superluminal light propagation via incoherent pump field
We investigate the dispersion and the absorption properties of a weak probe
field in a three-level Lambda-type atomic system. We use just an incoherent
field for controlling the group velocity of light. It is shown that the slope
of dispersion changes from positive to negative just with changing the
intensity of the indirect incoherent pumping field. Gain-assisted superluminal
light propagation appears in this system. No laser field is used in the pumping
processes
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