575 research outputs found
Soliton-radiation trapping in gas-filled photonic crystal fibers
We propose an optical trapping technique in which a fundamental soliton traps an ultrashort small amplitude radiation in a symmetric hollow-core photonic crystal fiber filled with a noble gas, preventing its dispersion. The system is Raman- and plasma-free. Trapping is due to the cross phase modulation effect between the two pulses. The trapped radiation inside the soliton-induced potential will oscillate periodically due to the shock effect, similar to the motion of a mechanical pendulum. DOI: 10.1103/PhysRevA.87.04380
Trapped Bose-Einstein condensates in the presence of a current nonlinearity
We investigate the effect of a current nonlinearity on the evolution of a
trapped atomic Bose-Einstein condensate. We have implemented techniques from
the field of nonlinear optics to provide new insights into the irregular
dynamics associated with chiral superfluids. We have found that the current
nonlinearity can be treated as a Kerr-like nonlinearity modulated by a
spatiotemporal function that can lead to a number of processes such as
broadening and compression of the wave function. In the long time scale limit,
the wave function is drastically deformed and delocalised compared to its
initial state. However, localised modes which oscillate with the period of the
inverse trap frequency can still be observed.Comment: A short note on the links between nonlinear gauge potentials and
nonlinear optics. Comments are welcom
Soliton dynamics in gas-filled hollow-core photonic crystal fibers
Gas-filled hollow-core photonic crystal fibers offer unprecedented
opportunities to observe novel nonlinear phenomena. The various properties of
gases that can be used to fill these fibers give additional degrees of freedom
for investigating nonlinear pulse propagation in a wide range of different
media. In this review, we will consider some of the the new nonlinear
interactions that have been discovered in recent years, in particular those
which are based on soliton dynamics
Modelling spontaneous four-wave mixing in periodically-tapered waveguides
Periodically-tapered-waveguides technique is an emerging potential route to
establish quasi-phase-matching schemes for efficient on-demand parametric
interactions in third-order nonlinear materials. In this paper, I investigate
this method in enhancing spontaneous photon-pairs emission in fibres and planar
waveguides with sinusoidally-varying cross sections. I have developed a general
robust quantum model to study this process under continuous or pulsed-pump
excitations. The model shows a great enhancement in photon-pairs generation in
waveguides with a small number of tapering periods that are feasible via the
current fabrication technologies. I envisage that this work will open a new
area of research to investigate how the tapering patterns can be fully
optimised to tailor the spectral properties of the output photons in
third-order nonlinear guided structures
Photonic circuits for generating modal, spectral, and polarization entanglement
We consider the design of photonic circuits that make use of Ti:LiNbO
diffused channel waveguides for generating photons with various combinations of
modal, spectral, and polarization entanglement. Down-converted photon pairs are
generated via spontaneous optical parametric down-conversion (SPDC) in a
two-mode waveguide. We study a class of photonic circuits comprising: 1) a
nonlinear periodically poled two-mode waveguide structure, 2) a set of
single-mode and two-mode waveguide-based couplers arranged in such a way that
they suitably separate the three photons comprising the SPDC process, and, for
some applications, 3) a holographic Bragg grating that acts as a dichroic
reflector. The first circuit produces frequency-degenerate down-converted
photons, each with even spatial parity, in two separate single-mode waveguides.
Changing the parameters of the elements allows this same circuit to produce two
nondegenerate down-converted photons that are entangled in frequency or
simultaneously entangled in frequency and polarization. The second photonic
circuit is designed to produce modal entanglement by distinguishing the photons
on the basis of their frequencies. A modified version of this circuit can be
used to generate photons that are doubly entangled in mode number and
polarization. The third photonic circuit is designed to manage dispersion by
converting modal, spectral, and polarization entanglement into path
entanglement
Strong Raman-induced non-instantaneous soliton interactions in gas-filled photonic crystal fibers
We have developed an analytical model based on the perturbation theory in
order to study the optical propagation of two successive intense solitons in
hollow-core photonic crystal fibers filled with Raman-active gases. Based on
the time delay between the two solitons, we have found that the trailing
soliton dynamics can experience unusual nonlinear phenomena such as spectral
and temporal soliton oscillations and transport towards the leading soliton.
The overall dynamics can lead to a spatiotemporal modulation of the refractive
index with a uniform temporal period and a uniform or chirped spatial period
Ultra-broadband supercontinuum generation in gas-filled photonic-crystal fibers: The epsilon-near-zero regime
In this Letter, we show theoretically that the nonlinear photoionisation
process of a noble gas inside a hollow-core photonic crystal fibre can be
exploited in obtaining broadband supercontinuum generation via pumping close to
the mid-infrared regime. The interplay between the Kerr and photoionisation
nonlinearities is strongly enhanced in this regime. Photoionisation
continuously modifies the medium dispersion, in which the refractive index
starts to significantly decrease and approach the epsilon-near-zero regime.
Subsequently, the self-phase modulation induced by the Kerr effect is boosted
because of the accompanied slow-light effect. As a result of this interplay, an
output spectrum that comprises of a broadband light with multiple
dispersive-wave emission is obtained.Comment: 5 pages, 5 figure
Modal, spectral, and polarization entanglement in guided-wave parametric down-conversion
We examine the modal, spectral, and polarization entanglement properties of photon pairs generated in a nonlinear periodically poled two-mode waveguide (one-dimensional planar or two-dimensional circular) via nondegenerate spontaneous parametric down-conversion. Any of the possible degrees of freedom-mode number, frequency, or polarization-can be used to distinguish the down-converted photons while the others serve as attributes of entanglement. Distinguishing the down-converted photons based on their mode numbers enables us to efficiently generate spectral or polarization entanglement that is either narrowband or broadband. On the other hand, when the generated photons are distinguished by their frequencies in a type-0 process, modal entanglement turns out to be an efficient alternative to polarization entanglement. Moreover, modal entanglement in type-II down-conversion may be used to generate a doubly entangled state in frequency and polarization
High-energy, shock-front assisted resonant radiation in the normal dispersion regime
We present a simple yet effective theory that predicts the existence of
resonant radiation bands in the deep normal group velocity dispersion region of
a medium, even in absence of a zero-group velocity dispersion point. This
radiation is evident when the medium is pumped with high-energy ultrashort
pulses, and it is driven by the interplay between the Kerr and the shock terms
in the NLSE. Accurate experiments performed in bulk silica fully support the
theoretical phase-matching condition found by our theory.Comment: 5 pages, 3 figure
Shock-induced PT -symmetric potentials in gas-filled photonic-crystal fibers
We have investigated the interaction between a strong soliton and a weak probe with certain configurations that allow optical trapping in gas-filled hollow-core photonic-crystal fibers in the presence of the shock effect. We have shown theoretically and numerically that the shock term can lead to an unbroken parity-time-(PT-) symmetric potential in these kinds of fibers. Time irreversible behavior, a signature feature of the PT symmetry, is also demonstrated numerically. Our results will open different configurations and avenues for observing PT-symmetry breaking in optical fibers, without the need to resort to complex optical systems
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