68 research outputs found
Diffractive optics approach towards subwavelength pixels
Pixel size in cameras and other refractive imaging devices is typically
limited by the free-space diffraction. However, a vast majority of
semiconductor-based detectors are based on materials with substantially high
refractive index. We demonstrate that diffractive optics can be used to take
advantage of this high refractive index to reduce effective pixel size of the
sensors below free-space diffraction limit. At the same time, diffractive
systems encode both amplitude and phase information about the incoming beam
into multiple pixels, offering the platform for noise-tolerant imaging with
dynamical refocusing. We explore the opportunities opened by high index
diffractive optics to reduce sensor size and increase signal-to-noise ratio of
imaging structures.Comment: submitted to SPIE-DCS 201
Nonlocal Optics of Plasmonic Nanowire Metamaterials
We present an analytical description of the nonlocal optical response of
plasmonic nanowire metamaterials that enable negative refraction, subwavelength
light manipulation, and emission lifetime engineering. We show that dispersion
of optical waves propagating in nanowire media results from coupling of
transverse and longitudinal electromagnetic modes supported by the composite
and derive the nonlocal effective medium approximation for this dispersion. We
derive the profiles of electric field across the unit cell, and use these
expressions to solve the long-standing problem of additional boundary
conditions in calculations of transmission and reflection of waves by nonlocal
nanowire media. We verify our analytical results with numerical solutions of
Maxwell's equations and discuss generalization of the developed formalism to
other uniaxial metamaterials
Non-magnetic nano-composites for optical and infrared negative refraction index media
We develop an approach to use nanostructured plasmonic materials as a
non-magnetic negative-refractive index system at optical and near-infrared
frequencies. In contrast to conventional negative refraction materials, our
design does not require periodicity and thus is highly tolerant to fabrication
defects. Moreover, since the proposed materials are intrinsically non-magnetic,
their performance is not limited to proximity of a resonance so that the
resulting structure has relatively low loss. We develop the analytical
description of the relevant electromagnetic phenomena and justify our analytic
results via numerical solutions of Maxwell equations
Meta-material photonic funnels for sub-diffraction light compression and propagation
We present waveguides with photonic crystal cores, supporting energy
propagation in subwavelength regions with a mode structure similar to that in
telecom fibers. We design meta-materials for near-, mid-, and far-IR
frequencies, and demonstrate efficient energy transfer to and from regions
smaller than 1/25-th of the wavelength. Both positive- and negative-refractive
index light transmissions are shown. Our approach, although demonstrated here
in circular waveguides for some specific frequencies, is easily scalable from
optical to IR to THz frequency ranges, and can be realized in a variety of
waveguide geometries. Our design may be used for ultra high-density energy
focusing, nm-resolution sensing, near-field microscopy, and high-speed
all-optical computing.Comment: 4 pages, 3 figures, texify read
Non-magnetic left-handed material
We develop a new approach to build a material with negative refraction index.
In contrast to conventional designs which make use of a resonant behavior to
achieve a non-zero magnetic response, our material is intrinsically
non-magnetic and relies on an anisotropic dielectric constant to provide a
left-handed response in waveguide geometry. We demonstrate that the proposed
material can support surface (polariton) waves, and show the connection between
polaritons and the enhancement of evanescent fields, also referred to as
super-lensing
Active metamaterials: sign of refraction index and gain-assisted dispersion management
We derive an approach to define the causal direction of the wavevector of
modes in optical metamaterials, which in turn, determines signs of refractive
index and impedance as a function of {\it real and imaginary} parts of
dielectric permittivity and magnetic permeability. We use the developed
technique to demonstrate that the interplay between resonant response of
constituents of metamaterials can be used to achieve efficient dispersion
management. Finally we demonstrate broadband dispersion-less index and
impedance matching in active nanowire-based negative index materials. Our work
opens new practical applications of negative index composites for broadband
lensing, imaging, and pulse-routing
Sub-diffraction light propagation in fibers with anisotropic dielectric cores
We present a detailed study of light propagation in waveguides with
anisotropic metamaterial cores. We demonstrate that in contrast to conventional
optical fibers, our structures support free-space-like propagating modes even
when the waveguide radius is much smaller than the wavelength. We develop
analytical formalism to describe mode structure and propagation in strongly
anisotropic systems and study the effects related to waveguide boundaries and
material composition
Gain-assisted slow to superluminal group velocity manipulation in nano-waveguides
We study the energy propagation in subwavelength waveguides and demonstrate
that the mechanism of material gain, previously suggested for loss
compensation, is also a powerful tool to manipulate dispersion and propagation
characteristics of electromagnetic pulses at the nanoscale. We show
theoretically that the group velocity in lossy nano-waveguides can be
controlled from slow to superluminal values by the material gain and waveguide
geometry and develop an analytical description of the relevant physics. We
utilize the developed formalism to show that gain-assisted dispersion
management can be used to control the transition between ``photonic-funnel''
and ``photonic-compressor'' regimes in tapered nano-waveguides. The phenomenon
of strong modulation of group velocity in subwavelength structures can be
realized in waveguides with different geometries, and is present for both
volume and surface-modes.Comment: Some changes in the abstract and Fig.1. No results affecte
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