1,622 research outputs found
Anomalous optical coupling between two silicon wires of a slot waveguide in epsilon-near-zero metamaterials
Anomalous optical coupling properties between two silicon wires in a silicon
slot waveguide embedded in epsilon-near-zero (ENZ) metamaterials are proposed
and demonstrated. The dependences of optical field enhancement in the slot
region and transverse optical force on the slot size and the permittivity of
surrounding material are studied in details. It is demonstrated that the
optical field in the slot region is significantly enhanced due to the giant
index contrast at the slot interface between silicon wires and ENZ
metamaterials, but the optical mode coupling between silicon wires is greatly
reduced so that the transverse optical force is suppressed into almost zero.
Moreover, metal-dielectric multilayer structures are designed to realize ENZ
metamaterials in the slot region for achieving the electric field enhancement.Comment: 14 pages, 5 figure
Realizing broadband electromagnetic transparency with a graded-permittivity sphere
Broadband electromagnetic transparency phenomenon is realized with a
well-designed graded-permittivity sphere, which has an extremely low scattering
cross section over a wide frequency range, based on the generalized Mie
scattering theory and numerical simulation in full-wave condition. The dynamic
polarization cancellation is revealed by studying the variation of the
polarization with respect to the frequency. Furthermore, a properly-designed
multi-shell sphere is also proposed and examined in order to reduce the
rigorous conditions for realizing the broadband transparency in experiments.Comment: 15 pages, 4 figure
Broadband Epsilon-Near-Zero Metamaterials with Step-Like Metal-Dielectric Multilayer Structures
The concept of the broadband epsilon-near-zero meta-atom consisting of
layered stacks with specified metallic filling ratio and thickness is proposed
based on the Bergman spectral representation of the effective permittivity. The
step-like metal-dielectric multilayer structures are designed to achieve
realistic broadband epsilon-near-zero meta-atoms in optical frequency range.
These meta-atoms can be integrated as building blocks for unconventional
optical components with exotic electromagnetic properties over a wide frequency
range, such as the demonstrated broadband directional emission and phase front
shaping.Comment: 18 pages, 7 figure
Stochastic Answer Networks for Machine Reading Comprehension
We propose a simple yet robust stochastic answer network (SAN) that simulates
multi-step reasoning in machine reading comprehension. Compared to previous
work such as ReasoNet which used reinforcement learning to determine the number
of steps, the unique feature is the use of a kind of stochastic prediction
dropout on the answer module (final layer) of the neural network during the
training. We show that this simple trick improves robustness and achieves
results competitive to the state-of-the-art on the Stanford Question Answering
Dataset (SQuAD), the Adversarial SQuAD, and the Microsoft MAchine Reading
COmprehension Dataset (MS MARCO).Comment: 11 pages, 5 figures, Accepted to ACL 201
Depth Assisted Full Resolution Network for Single Image-based View Synthesis
Researches in novel viewpoint synthesis majorly focus on interpolation from
multi-view input images. In this paper, we focus on a more challenging and
ill-posed problem that is to synthesize novel viewpoints from one single input
image. To achieve this goal, we propose a novel deep learning-based technique.
We design a full resolution network that extracts local image features with the
same resolution of the input, which contributes to derive high resolution and
prevent blurry artifacts in the final synthesized images. We also involve a
pre-trained depth estimation network into our system, and thus 3D information
is able to be utilized to infer the flow field between the input and the target
image. Since the depth network is trained by depth order information between
arbitrary pairs of points in the scene, global image features are also involved
into our system. Finally, a synthesis layer is used to not only warp the
observed pixels to the desired positions but also hallucinate the missing
pixels with recorded pixels. Experiments show that our technique performs well
on images of various scenes, and outperforms the state-of-the-art techniques
Learning Semantic Representations for the Phrase Translation Model
This paper presents a novel semantic-based phrase translation model. A pair
of source and target phrases are projected into continuous-valued vector
representations in a low-dimensional latent semantic space, where their
translation score is computed by the distance between the pair in this new
space. The projection is performed by a multi-layer neural network whose
weights are learned on parallel training data. The learning is aimed to
directly optimize the quality of end-to-end machine translation results.
Experimental evaluation has been performed on two Europarl translation tasks,
English-French and German-English. The results show that the new semantic-based
phrase translation model significantly improves the performance of a
state-of-the-art phrase-based statistical machine translation sys-tem, leading
to a gain of 0.7-1.0 BLEU points
Quantum entanglement in plasmonic waveguides with near-zero mode indices
We investigate the quantum entanglement between two quantum dots in a
plasmonic waveguide with near-zero mode index, considering the dependence of
concurrence on interdot distance, quantum dot-waveguide frequency detuning and
coupling strength ratio. High concurrence is achieved for a wide range of
interdot distance due to the near-zero mode index, which largely relaxes the
strict requirement of interdot distance in conventional dielectric waveguides
or metal nanowires. The proposed quantum dot-waveguide system with near-zero
phase variation along the waveguide near the mode cutoff frequency shows very
promising potential in quantum optics and quantum information processing
- …