183 research outputs found
Translation of Nanoantenna Hot-Spots by a Metal-Dielectric Composite Superlens
We employ numerical simulations to show that highly localized, enhanced
electromagnetic fields, also known as "hot spots," produced by a periodic array
of silver nanoantennas can be spatially translated to the other side of a
metal-dielectric composite superlens. The proposed translation of the hot spots
enables surface-enhanced optical spectroscopy without the undesirable contact
of molecules with metal, and thus it broadens and reinforces the potential
applications of sensing based on field-enhanced fluorescence and
surface-enhanced Raman scattering.Comment: 9 pages, 4 figure
Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications
Optical properties of colloidal plasmonic titanium nitride nanoparticles are
examined with an eye on their photothermal via transmission electron microscopy
and optical transmittance measurements. Single crystal titanium nitride cubic
nanoparticles with an average size of 50 nm exhibit plasmon resonance in the
biological transparency window. With dimensions optimized for efficient
cellular uptake, the nanoparticles demonstrate a high photothermal conversion
efficiency. A self-passivating native oxide at the surface of the nanoparticles
provides an additional degree of freedom for surface functionalization.Comment: 17 pages, 4 figures, 1 abstract figur
Trapped Rainbow Techniques for Spectroscopy on a Chip and Fluorescence Enhancement
We report on the experimental demonstration of the broadband "trapped
rainbow" in the visible range using arrays of adiabatically tapered optical
nano waveguides. Being a distinct case of the slow light phenomenon, the
trapped rainbow effect could be applied to optical signal processing, and
sensing in such applications as spectroscopy on a chip, and to providing
enhanced light-matter interactions. As an example of the latter applications,
we have fabricated a large area array of tapered nano-waveguides, which exhibit
broadband "trapped rainbow" effect. Considerable fluorescence enhancement due
to slow light behavior in the array has been observed.Comment: 15 pages, 4 figures, Published in Applied Physics
The art of finding the optimal scattering center(s)
The efficient use of a multipole expansion of the far field for rapid
numerical modeling and optimization of the optical response from ordered and
disordered arrays of various structural elements is complicated by the
ambiguity in choosing the ultimate expansion centers for individual scatterers.
Since the multipolar decomposition depends on the position of the expansion
center, the sets of multipoles are not unique. They may require constrained
optimization to get the compact and most efficient spatial spectrum for each
scatterer. We address this problem by finding {\em the optimal scattering
centers} for which the spatial multipolar spectra become unique. We separately
derive these optimal positions for the electric and magnetic parts by
minimizing the norm of the poloidal electric and magnetic quadrupoles.
Employing the long-wave approximation (LWA) ansatz, we verify the approach with
the theoretical discrete models and realistic scatterers. We show that the
optimal electric and magnetic scattering centers, in all cases, are not
co-local with the centers of mass. The optimal multipoles, including the
toroidal terms, are calculated for several structurally distinct scattering
cases, and their utility for low-cost numerical schemes, including the
generalized T-matrix approach, is discussed. Expansion of the work beyond the
LWA is possible, with a promise for faster and universal numerical schemes
Plasmonic waveguides cladded by hyperbolic metamaterials
Strongly anisotropic media with hyperbolic dispersion can be used for
claddings of plasmonic waveguides. In order to analyze the fundamental
properties of such waveguides, we analytically study 1D waveguides arranged of
a hyperbolic metamaterial (HMM) in a HMM-Insulator-HMM (HIH) structure. We show
that hyperbolic metamaterial claddings give flexibility in designing the
properties of HIH waveguides. Our comparative study on 1D plasmonic waveguides
reveals that HIH-type waveguides can have a higher performance than MIM or IMI
waveguides
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