58 research outputs found
Geometric interpretations for resonances of plasmonic nanoparticles
The rapidly developing field of plasmonics can be roughly categorized into
two branches: surface plasmon polaritons (SPPs) propagating in plasmonic
waveguides and localized surface plasmons (LSPs) supported by scattering
plasmonic particles. Investigations along these two directions usually employ
quite different approaches and techniques, resulting in more or less a dogma
that the two branches progress almost independently of each other, with few
interactions. Here in this work we interpret LSPs from a Bohr model based
geometric perspective relying on SPPs, thus establishing a connection between
these two sub-fields. Besides the clear explanations of conventional scattering
features of plasmonic nanoparticles, based on this geometric model we further
demonstrate other anomalous scattering features (higher order modes supported
at lower frequencies, and blueshift of the resonance with increasing particle
sizes) and multiple electric resonances of the same order supported at
different frequencies, which have been revealed to originate from backward SPP
modes and multiple dispersion bands supported in the corresponding plasmonic
waveguides, respectively. Inspired by this geometric model, it is also shown
that, through solely geometric tuning, the absorption of each LSP resonance can
be maximized to reach the single channel absorption limit, provided that the
scattering and absorption rates are tuned to be equal. The Bohr model based
geometric picture offers new insights into the understanding of the localized
resonances, and may shed new light to many related applications based on
particle scattering, such as biosensing, nanoantennas, photovoltaic devices and
related medical treatment.Comment: To appear in Scientific Reports. Related information could also be
found at: http://digitalcollections.anu.edu.au/handle/1885/1030
Scattering of core-shell nanowires with the interference of electric and magnetic resonances
We study the scattering of normally incident waves by core-shell nanowires, which support both electric and magnetic resonances. Within such nanowires, for p-polarized incident waves, each electric resonance corresponds to two degenerate scattering channels while the magnetic resonance corresponds to only one channel. Consequently, when the electric dipole (ED) and magnetic dipole (MD) are tuned to overlap spectrally, the magnitude of the ED is twice that of the magnetic one, leading to a pair of angles of vanishing scattering. We further demonstrate that the scattering features of nanowires are polarization dependent, and vanishing scattering angles also can be induced by Fano resonances due to the interference of higher-order electric modes with the broad MD mode.We thank S. Deng for useful discussions and acknowledge
support from the Australian Research Council and
the Leverhulme Trust
Breakdown of Temporal Coherence in Photon Condensates
The temporal coherence of an ideal Bose gas increases as the system
approaches the Bose-Einstein condensation threshold from below, with coherence
time diverging at the critical point. However, counter-examples have been
observed for condensates of photons formed in an externally pumped, dye-filled
microcavity, wherein the coherence time decreases rapidly for increasing
particle number above threshold. This paper establishes intermode correlations
as the central explanation for the experimentally observed dramatic decrease in
the coherence time beyond critical pump power.Comment: 5 pages, 4 figure
Photon-photon correlation of condensed light in a microcavity
The study of temporal coherence in a Bose-Einstein condensate of photons can
be challenging, especially in the presence of correlations between the photonic
modes. In this work, we use a microscopic, multimode model of photonic
condensation inside a dye-filled microcavity and the quantum regression
theorem, to derive an analytical expression for the equation of motion of the
photon-photon correlation function. This allows us to derive the coherence time
of the photonic modes and identify a nonmonotonic dependence of the temporal
coherence of the condensed light with the cutoff frequency of the microcavity.Comment: 12 pages, 5 figure
Learning the Fuzzy Phases of Small Photonic Condensates
Phase transitions, being the ultimate manifestation of collective behaviour,
are typically features of many-particle systems only. Here, we describe the
experimental observation of collective behaviour in small photonic condensates
made up of only a few photons. Moreover, a wide range of both equilibrium and
non-equilibrium regimes, including Bose-Einstein condensation or laser-like
emission are identified. However, the small photon number and the presence of
large relative fluctuations places major difficulties in identifying different
phases and phase transitions. We overcome this limitation by employing
unsupervised learning and fuzzy clustering algorithms to systematically
construct the fuzzy phase diagram of our small photonic condensate. Our results
thus demonstrate the rich and complex phase structure of even small collections
of photons, making them an ideal platform to investigate equilibrium and
non-equilibrium physics at the few particle level
Room temperature plasmon laser by total internal reflection
Plasmon lasers create and sustain intense and coherent optical fields below
light's diffraction limit with the unique ability to drastically enhance
light-matter interactions bringing fundamentally new capabilities to
bio-sensing, data storage, photolithography and optical communications.
However, these important applications require room temperature operation, which
remains a major hurdle. Here, we report a room temperature semiconductor
plasmon laser with both strong cavity feedback and optical confinement to
1/20th of the wavelength. The strong feedback arises from total internal
reflection of surface plasmons, while the confinement enhances the spontaneous
emission rate by up to 20 times.Comment: 8 Page, 2 Figure
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