13,455 research outputs found
An Optimization Method of Asymmetric Resonant Cavities for Unidirectional Emission
In this paper, we studied the repeatability and accuracy of the ray
simulation for one kind of Asymmetric Resonant Cavities (ARCs)
Half-Quadrupole-Half-Circle shaped cavity, and confirmed the robustness of the
directionality about the shape errors. Based on these, we proposed a
hill-climbing algorithm to optimize the ARCs for unidirectional emission.
Different evaluation functions of directionality were tested and we suggested
using the function of energy contained in a certain angle for highly collimated
and unidirect ional emission. By this method, we optimized the ARCs to obtain
about 0.46 of the total radiated energy in divergence angle of 40 degree in the
far field. This optimization method is very powerful for the shape engineering
of ARCs and could be applied in future studies of ARCs with specific emission
properties
Dynamic process of free space excitation of asymmetry resonant microcavity
The underlying physics and detailed dynamical processes of the free space
beam excitation to the asymmetry resonant microcavity are studied numerically.
Taking the well-studied quadrupole deformed microcavity as an example, we use a
Gaussian beam to excite the high-Q mode. The simulation provides a powerful
platform to study the underlying physics. The transmission spectrum and
intracavity energy can be obtained directly. Irregular transmission spectrum
was observed, showing asymmetric Fano-type lineshapes which could be attributed
to interference between the different light paths. Then excitation efficiencies
about the aim distance of the incident Gaussian beam and the rotation angle of
the cavity were studied, showing great consistence with the reversal of
emission efficiencies. By projecting the position dependent excitation
efficiency to the phase space, the correspondence between the excitation and
emission was demonstrated. In addition, we compared the Husimi distributions of
the excitation processes and provided more direct evidences of the dynamical
tunneling process in the excitation process
Discord and entanglement in non-Markovian environments at finite temperature
The dynamics evolutions of discord and entanglement of two atoms in two
independent Lorentzian reservoirs at zero or finite temperature have been
investigated by using the time-convolutionless master-equation method. Our
results show that, when both the non-Markovian effect and the detuning are
present simultaneously, due to the memory and feedback effect of the
non-Markovian reservoirs, the discord and the entanglement can be effectively
protected even at nonzero temperature by increasing the non-Markovian effect
and the detuning. The discord and the entanglement have different robustness
for different initial states and their robustness may changes under certain
conditions. Nonzero temperature can accelerate the decays of discord and
entanglement and induce the entanglement sudden death.Comment: 13 pages, 6 figure
Squeezing of light field in a dissipative Jaynes-Cummings model
Based on the time-convolutionless master-equation approach, we investigate
squeezing of light field in a dissipative Jaynes-Cummings model. The results
show that squeezing light can be generated when the atom transits to a ground
state from an excited state, and then a collapse-revival phenomenon will occur
in the squeezing of light field due to atom-cavity coupling. Enhancing the
atom-cavity coupling can increase the frequency of the collapse-revival of
squeezing. The stronger the non-Markovian effect is, the more obvious the
collapse-revival phenomenon is. The oscillatory frequency of the squeezing is
dependents on the resonant frequency of the atom-cavity
Analytical solution and entanglement swapping of a double Jaynes-Cummings model in non-Markovian environments
Analytical solution and entanglement swapping of a double Jaynes-Cummings
model in non-Markovian environments are investigated by the timeconvolutionless
master equation method. We obtain the analytical solution of this model and
discuss in detail the influence of atom-cavity coupling, non-Markovian effect
and initial state purity on entanglement dynamics. The results show that, in
the non-Markovian environments, the entanglement between two cavities can be
swapped to other bipartite subsystems by interaction between an atom and its
own cavity. Due to the dissipation of environment, the entanglements of all
bipartite subsystems will eventually decay to zero when the atom couples weakly
to its cavity and the non-Markovian effect is also weak. All bipartite
subsystems can tend to steady entanglement states if and only if there is the
strong atom-cavity coupling or the strong non-Markovian effect. The steady
state of the subsystem composed of an atom and its own cavity is independent on
the purity but the steady states of other bipartite subsystems are dependent on
the purity.Comment: 14 pages, 9 figures
Chiral Symmetry Breaking in Micro-Ring Optical Cavity By Engineered Dissipation
We propose a method to break the chiral symmetry of light in traveling wave
resonators by coupling the optical modes to a lossy channel. Through the
engineered dissipation, an indirect dissipative coupling between two oppositely
propagating modes can be realized. Combining with reactive coupling, it can
break the chiral symmetry of the resonator, allowing light propagating only in
one direction. The chiral symmetry breaking is numerically verified by the
simulation of an electromagnetic field in a micro-ring cavity, with proper
refractive index distributions. This work provokes us to emphasize the
dissipation engineering in photonics, and the generalized idea can also be
applied to other systems.Comment: 6 pages, 3 figure
On a two-component Bose-Einstein condensate with steep potential wells
In this paper, we study the following two-component systems of nonlinear
Schr\"odinger equations \begin{equation*} \left\{\aligned&\Delta u-(\lambda
a(x)+a_0(x))u+\mu_1u^3+\beta v^2u=0\quad&\text{in }\bbr^3,\\ &\Delta v-(\lambda
b(x)+b_0(x))v+\mu_2v^3+\beta u^2v=0\quad&\text{in }\bbr^3,\\ &u,v\in\h,\quad
u,v>0\quad\text{in }\bbr^3,\endaligned\right. \end{equation*} where
and are parameters; are
steep potentials and are sign-changing weight functions;
, , and are not necessarily to be radial
symmetric. By the variational method, we obtain a ground state solution and
multi-bump solutions for such systems with sufficiently large. The
concentration behaviors of solutions as both and
are also considered. In particular, the phenomenon of phase
separations is observed in the whole space \bbr^3. In the Hartree-Fock
theory, this provides a theoretical enlightenment of phase separation in
\bbr^3 for the 2-mixtures of Bose-Einstein condensates.Comment: 39 page
Extremely local electric field enhancement and light confinement in dielectric waveguide
The extremely local electric field enhancement and light confinement is
demonstrated in dielectric waveguide with corner and gap geometry. The
numerical results reveal the local electric field enhancement in the vicinity
of the apex of fan-shaped waveguide. Classical electromagnetic theory predicts
that the field enhancement and confinement abilities increase with decreasing
radius of rounded corner () and gap (), and show singularity for
infinitesimal and . For practical parameters with ,
the mode area of opposing apex-to-apex fan-shaped waveguides can be as small as
(), far beyond the diffraction
limit. This way of breaking diffraction limit with no loss outperforms
plasmonic waveguides, where light confinement is realized at the cost of huge
intrinsic loss in the metal. Furthermore, we propose a structure with
dielectric bow-tie antenna on a silicon-on-insulator waveguide, whose field
enhancement increases by one order. The lossless dielectric corner and gap
structures offer an alternative method to enhance the light-matter interaction
without metal nano-structure, and will find applications in quantum
electrodynamics, sensors and nano-particle trapping.Comment: 9 pages, 6 figure
Quantum coherence and non-Markovianity of atom in dissipative cavity under weak measurement
Quantum coherence and non-Markovianity of an atom in dissipative cavity under
weak measurement are investigated in this work. We find that, the quantum
coherence obviously depends on the atomic initial state, the strength of the
weak measurement and its reversal, the atom-cavity coupling constant and the
non-Markovian effecct. The more obvious the weak measurement effect is, the
better the protection of coherence is. The quantum coherence is preserved more
efficiently for lager the atom-cavity coupling. The stronger the non-Markovian
effect, the more slowly the coherence reduces. This is, the quantum coherence
can be effectively protected by means of controlling these physical parameters.Comment: 11 pages, 7 figure
Dielectric Bow-tie Nanocavity
We propose a novel dielectric bow-tie nanocavity consisting of two tip-to-tip
opposite triangle semiconductor nanowires, whose end faces are coated by silver
nanofilms. Based on the advantages of the dielectric slot and tip structures,
and the high reflectivity from the silver mirror, light can be confined in this
nanocavity with low loss. We demonstrate that the mode excited in this
nanocavity has a deep subwavelength mode volume of 2.8*10^-4 um3 and a high
quality factor of 4.9*10^4 (401.3), consequently an ultrahigh Purcell factor of
1.6*10^7 (1.36*10^5), at 4.5 K (300 K) around the resonance wavelength of 1550
nm. This dielectric bow-tie nanocavity may find applications for integrated
nanophotonic circuits, such as high-efficiency single photon source,
thresholdless nanolaser, and cavity QED strong coupling experiments.Comment: 3 pages, 4 figure
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