424 research outputs found
Exceptional points in parity-time symmetric plasmonic Huygens metasurfaces
Parity-Time (PT) symmetric optical structures exhibit several unique and
interesting characteristics with the most popular being exceptional points.
While the emerging concept of PT-symmetry has been extensively investigated in
bulky photonic designs, its exotic functionalities in nanophotonic
non-Hermitian plasmonic systems still remain relatively unexplored. Towards
this goal, in this work we analyze the unusual properties of a plasmonic
Huygens metasurface composed of an array of active metal-dielectric core-shell
nanoparticles. By calculating the reflection and transmission coefficients of
the metasurface under various levels of gain, we demonstrate the existence of
reflectionless transmission when an exceptional point is formed. The proposed
new active metasurface design has subwavelength thickness and can be used to
realize ultracompact perfect transmission optical filters
Losses in plasmonics: from mitigating energy dissipation to embracing loss-enabled functionalities
Unlike conventional optics, plasmonics enables unrivalled concentration of
optical energy well beyond the diffraction limit of light. However, a
significant part of this energy is dissipated as heat. Plasmonic losses present
a major hurdle in the development of plasmonic devices and circuits that can
compete with other mature technologies. Until recently, they have largely kept
the use of plasmonics to a few niche areas where loss is not a key factor, such
as surface enhanced Raman scattering and biochemical sensing. Here, we discuss
the origin of plasmonic losses and various approaches to either minimize or
mitigate them based on understanding of fundamental processes underlying
surface plasmon modes excitation and decay. Along with the ongoing effort to
find and synthesize better plasmonic materials, optical designs that modify the
optical powerflow through plasmonic nanostructures can help in reducing both
radiative damping and dissipative losses of surface plasmons. Another strategy
relies on the development of hybrid photonic-plasmonic devices by coupling
plasmonic nanostructures to resonant optical elements. Hybrid integration not
only helps to reduce dissipative losses and radiative damping of surface
plasmons, but also makes possible passive radiative cooling of nano-devices.
Finally, we review emerging applications of thermoplasmonics that leverage
Ohmic losses to achieve new enhanced functionalities. The most successful
commercialized example of a loss-enabled novel application of plasmonics is
heat-assisted magnetic recording. Other promising technological directions
include thermal emission manipulation, cancer therapy, nanofabrication,
nano-manipulation, plasmon-enabled material spectroscopy and thermo-catalysis,
and solar water treatment.Comment: 43 pages, 18 figure
Multi-mode lasing in supercell plasmonic nanoparticle arrays
Multicolour light sources can be used in applications such as lighting and
multiplexing signals. In photonic and plasmonic systems, one way to achieve
multicolour light is via multi-mode lasing. To achieve this, plasmonic
nanoparticle arrays are typically arranged in superlattices that lead to
multiple dispersions of the single arrays coupled via the superlattice Bragg
modes. Here, we show an alternative way to enable multi-mode lasing in
plasmonic nanoparticle arrays. We design a supercell in a square lattice by
leaving part of the lattice sites empty. This results in multiple dispersive
branches caused by the supercell period and hence creates additional band edges
that can support lasing. We experimentally demonstrate multi-mode lasing in
such a supercell array. Furthermore, we identify the lasing modes by
calculating the dispersion by combining the structure factor of the array
design with an empty lattice approximation. We conclude that the lasing modes
are the 74th - and 106th -point of the supercell. By tuning the
square lattice period with respect to the gain emission we can control the
modes that lase. Finally, we show that the lasing modes exhibit a combination
of transverse electric and transverse magnetic mode characteristics in
polarization resolved measurements
Topological nanophotonics for photoluminescence control
Rare-earth doped nanocrystals are emerging light sources used for many
applications in nanotechnology enabled by human ability to control their
various optical properties with chemistry and material science. However, one
important optical problem -- polarisation of photoluminescence -- remains
largely out of control by chemistry methods. Control over photoluminescence
polarisation can be gained via coupling of emitters to resonant nanostructures
such as optical antennas and metasurfaces. However, the resulting polarization
is typically sensitive to position disorder of emitters, which is difficult to
mitigate. Recently, new classes of disorder-immune optical systems have been
explored within the framework of topological photonics. Here we explore
disorder-robust topological arrays of Mie-resonant nanoparticles for
polarisation control of photoluminescence of nanocrystals. We demonstrate
polarized emission from rare-earth-doped nanocrystals governed by photonic
topological edge states supported by zigzag arrays of dielectric resonators. We
verify the topological origin of polarised photoluminescence by comparing
emission from nanoparticles coupled to topologically trivial and nontrivial
arrays of nanoresonators
Topological plasmons in dimerized chains of nanoparticles: robustness against long-range quasistatic interactions and retardation effects
We present a simple model of collective plasmons in a dimerized chain of
spherical metallic nanoparticles, an elementary example of a topologically
nontrivial nanoplasmonic system. Taking into account long-range quasistatic
dipolar interactions throughout the chain, we provide an exact analytical
expression for the full quasistatic bandstructure of the collective plasmons.
An explicit calculation of the Zak phase proves the robustness of the
topological physics of the system against the inclusion of long-range Coulomb
interactions, despite the broken chiral symmetry. Using an open quantum systems
approach, which includes retardation through the plasmon-photon coupling, we go
on to analytically evaluate the resulting radiative frequency shifts of the
plasmonic spectrum. The bright plasmonic bands experience size-dependent
radiative shifts, while the dark bands are essentially unaffected by the
light-matter coupling. Notably, the upper transverse-polarized band presents a
logarithmic singularity where the quasistatic spectrum intersects the light
cone. At wavevectors away from this intersection and for subwavelength
nanoparticles, the plasmon-photon coupling only leads to a quantitative
reconstruction of the bandstructure and the topologically-protected states at
the edge of the first Brillouin zone are essentially unaffected.Comment: 15 pages, 6 figures, published versio
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