1,400 research outputs found
Single Photon Transport through an Atomic Chain Coupled to a One-dimensional Nanophotonic Waveguide
We study the dynamics of a single photon pulse travels through a linear
atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide.
We derive a time-dependent dynamical theory for this collective many-body
system which allows us to study the real time evolution of the photon transport
and the atomic excitations. Our analytical result is consistent with previous
numerical calculations when there is only one atom. For an atomic chain, the
collective interaction between the atoms mediated by the waveguide mode can
significantly change the dynamics of the system. The reflectivity of a photon
can be tuned by changing the ratio of coupling strength and the photon
linewidth or by changing the number of atoms in the chain. The reflectivity of
a single photon pulse with finite bandwidth can even approach . The
spectrum of the reflected and transmitted photon can also be significantly
different from the single atom case. Many interesting physical phenomena can
occur in this system such as the photonic bandgap effects, quantum entanglement
generation, Fano-like interference, and superradiant effects. For engineering,
this system may serve as a single photon frequency filter, single photon
modulation and may find important applications in quantum information
-Chain closing lemma for certain partially hyperbolic diffeomorphisms
For every , we prove a -orbit
connecting lemma for dynamically coherent and plaque expansive partially
hyperbolic diffeomorphisms with 1-dimensional orientation preserving center
bundle. To be precise, for such a diffeomorphism , if a point is chain
attainable from through pseudo-orbits, then for any neighborhood of
and any neighborhood of , there exist true orbits from to by
arbitrarily -small perturbations. As a consequence, we prove that for
-generic diffeomorphisms in this class, periodic points are dense in the
chain recurrent set, and chain transitivity implies transitivity
Disorder Improves Light Absorption in Thin Film Silicon Solar Cells with Hybrid Light Trapping Structure
We present a systematic simulation study on the impact of disorder in thin film silicon solar cells with hybrid light trapping structure. For the periodical structures introducing certain randomness in some parameters, the nanophotonic light trapping effect is demonstrated to be superior to their periodic counterparts. The nanophotonic light trapping effect can be associated with the increased modes induced by the structural disorders. Our study is a systematic proof that certain disorder is conceptually an advantage for nanophotonic light trapping concepts in thin film solar cells. The result is relevant to the large field of research on nanophotonic light trapping which currently investigates and prototypes a number of new concepts including disordered periodic and quasiperiodic textures. The random effect on the shape of the pattern (position, height, and radius) investigated in this paper could be a good approach to estimate the influence of experimental inaccuracies for periodic or quasi-periodic structures
Towards Ghost-free Shadow Removal via Dual Hierarchical Aggregation Network and Shadow Matting GAN
Shadow removal is an essential task for scene understanding. Many studies
consider only matching the image contents, which often causes two types of
ghosts: color in-consistencies in shadow regions or artifacts on shadow
boundaries. In this paper, we tackle these issues in two ways. First, to
carefully learn the border artifacts-free image, we propose a novel network
structure named the dual hierarchically aggregation network~(DHAN). It contains
a series of growth dilated convolutions as the backbone without any
down-samplings, and we hierarchically aggregate multi-context features for
attention and prediction, respectively. Second, we argue that training on a
limited dataset restricts the textural understanding of the network, which
leads to the shadow region color in-consistencies. Currently, the largest
dataset contains 2k+ shadow/shadow-free image pairs. However, it has only 0.1k+
unique scenes since many samples share exactly the same background with
different shadow positions. Thus, we design a shadow matting generative
adversarial network~(SMGAN) to synthesize realistic shadow mattings from a
given shadow mask and shadow-free image. With the help of novel masks or
scenes, we enhance the current datasets using synthesized shadow images.
Experiments show that our DHAN can erase the shadows and produce high-quality
ghost-free images. After training on the synthesized and real datasets, our
network outperforms other state-of-the-art methods by a large margin. The code
is available: http://github.com/vinthony/ghost-free-shadow-removal/Comment: Accepted by AAAI 202
- β¦