5,285 research outputs found
Maxwell-Bloch modeling of an x-ray pulse amplification in a 1D photonic crystal
We present an implementation of the Maxwell-Bloch (MB) formalism for the
study of x-ray emission dynamics from periodic multilayer materials whether
they are artificial or natural. The treatment is based on a direct
Finite-Difference-Time-Domain (FDTD) solution of Maxwell equations combined
with Bloch equations incorporating a random spontaneous emission noise. Besides
periodicity of the material, the treatment distinguishes between two kinds of
layers, those being active (or resonant) and those being off-resonance. The
numerical model is applied to the problem of emission in multilayer
materials where the population inversion could be created by fast inner-shell
photoionization by an x-ray free-electron-laser (XFEL). Specificities of the
resulting amplified fluorescence in conditions of Bragg diffraction is
illustrated by numerical simulations. The corresponding pulses could be used
for specific investigations of non-linear interaction of x-rays with matter
Manipulating Light Pulses via Dynamically Controlled Photonic Bandgap
When a resonance associated with electromagnetically induced transparency
(EIT) in an atomic ensemble is modulated by an off-resonant standing light
wave, a band of frequencies can appear for which light propagation is
forbidden. We show that dynamic control of such a bandgap can be used to
coherently convert a propagating light pulse into a stationary excitation with
non-vanishing photonic component. This can be accomplished with high efficiency
and negligble noise even at a level of few-photon quantum fields thereby
facilitating possible applications in quantum nonlinear optics and quantum
information.Comment: 4 pages, 3 figure
Shaping quantum pulses of light via coherent atomic memory
We describe a technique for generating pulses of light with controllable
photon numbers, propagation direction, timing, and pulse shapes. The technique
is based on preparation of an atomic ensemble in a state with a desired number
of atomic spin excitations, which is later converted into a photon pulse.
Spatio-temporal control over the pulses is obtained by exploiting long-lived
coherent memory for photon states and electromagnetically induced transparency
(EIT) in an optically dense atomic medium. Using photon counting experiments we
observe generation and shaping of few-photon sub-Poissonian light pulses. We
discuss prospects for controlled generation of high-purity n-photon Fock states
using this technique.Comment: 4 pages, 4 figure
Dynamic optical bistability in resonantly enhanced Raman generation
We report observations of novel dynamic behavior in resonantly-enhanced
stimulated Raman scattering in Rb vapor. In particular, we demonstrate a
dynamic hysteresis of the Raman scattered optical field in response to changes
of the drive laser field intensity and/or frequency. This effect may be
described as a dynamic form of optical bistability resulting from the formation
and decay of atomic coherence. We have applied this phenomenon to the
realization of an all-optical switch.Comment: 4 pages, 5 figure
Nonlinear optics with stationary pulses of light
We show that the recently demonstrated technique for generating stationary
pulses of light [Nature {\bf 426}, 638 (2003)] can be extended to localize
optical pulses in all three spatial dimensions in a resonant atomic medium.
This method can be used to dramatically enhance the nonlinear interaction
between weak optical pulses. In particular, we show that an efficient Kerr-like
interaction between two pulses can be implemented as a sequence of several
purely linear optical processes. The resulting process may enable coherent
interactions between single photon pulses.Comment: 4 pages, 2 figure
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