1,780 research outputs found
The effects of retardation on the topological plasmonic chain: plasmonic edge states beyond the quasistatic limit
We study a one-dimensional plasmonic system with non-trivial topology: a
chain of metallic nanoparticles with alternating spacing, which is the
plasmonic analogue to the Su-Schreiffer-Heeger model. We extend previous
efforts by including long range hopping with retardation and radiative damping,
which leads to a non-Hermitian Hamiltonian with frequency dependence. We
calculate band structures numerically and show that topological features such
as quantised Zak phase persist due to chiral symmetry. This predicts parameters
leading to topologically protected edge modes, which allows for positioning of
disorder-robust hotspots at topological interfaces, opening up novel
nanophotonics applications
Asymptotics of surface-plasmon redshift saturation at sub-nanometric separations
Many promising nanophotonics endeavours hinge upon the unique plasmonic
properties of nanometallic structures with narrow non-metallic gaps, which
support super-concentrated bonding modes that singularly redshift with
decreasing separations. In this letter, we present a descriptive physical
picture, complemented by elementary asymptotic formulae, of a nonlocal
mechanism for plasmon-redshift saturation at subnanometric gap widths. Thus, by
considering the electron-charge and field distributions in the close vicinity
of the metal-vacuum interface, we show that nonlocality is asymptotically
manifested as an effective potential discontinuity. For bonding modes in the
near-contact limit, the latter discontinuity is shown to be effectively
equivalent to a widening of the gap. As a consequence, the resonance-frequency
near-contact asymptotics are a renormalisation of the corresponding local ones.
Specifically, the renormalisation furnishes an asymptotic plasmon-frequency
lower bound that scales with the -power of the Fermi wavelength. We
demonstrate these remarkable features in the prototypical cases of nanowire and
nanosphere dimers, showing agreement between our elementary expressions and
previously reported numerical computations
Surface phonon polaritonics made simple: Great as plasmonics but lower losses
Phonon-polaritons offer an exciting avenue in nanophotonics. We comment on the novel nanofabrication approach presented by Bo Qiang et al. in this issue of Advanced Photonics. Their approach to phononic material allows better radiation manipulation, and high Q-factors
Surface-plasmon resonances of arbitrarily shaped nanometallic structures in the small-screening-length limit
According to the hydrodynamic Drude model, surface-plasmon resonances of
metallic nanostructures blueshift owing to the nonlocal response of the metal's
electron gas. The screening length characterising the nonlocal effect is often
small relative to the overall dimensions of the metallic structure, which
enables us to derive a coarse-grained nonlocal description using matched
asymptotic expansions; a perturbation theory for the blueshifts of arbitrary
shaped nanometallic structures is then developed. The effect of nonlocality is
not always a perturbation and we present a detailed analysis of the "bonding"
modes of a dimer of nearly touching nanowires where the leading-order
eigenfrequencies and eigenmode distributions are shown to be a renormalisation
of those predicted assuming a local metal permittivity
Casimir nanoparticle levitation in vacuum with broadband perfect magnetic conductor metamaterials
The levitation of nanoparticles is essential in various branches of research.
Casimir forces are natural candidates to tackle it but the lack of broadband
metamaterials precluded repulsive forces in vacuum. We show sub-micron
nanoparticle levitation in vacuum only based on the design of a broadband
metamaterial perfect magnetic conductor surface, where the force is mostly
given by the (quantum) zero-point contribution. In the harmonic regime of the
center of mass dynamics, the characteristic frequency depends linearly on
Planck's constant while independent of the nanoparticle's volume.Comment: 6 pages manuscript, with 3 figures; and 9 pages supplementary
material, with 2 figure
Resonant enhancement of second harmonic generation in the mid-infrared using localized surface phonon polaritons in sub-diffractional nanostructures
We report on strong enhancement of mid-infrared second harmonic generation
(SHG) from SiC nanopillars due to the resonant excitation of localized surface
phonon-polaritons within the Reststrahlen band. The magnitude of the SHG peak
at the monopole mode experiences a strong dependence on the resonant frequency
beyond that described by the field localization degree and the dispersion of
linear and nonlinear-optical SiC properties. Comparing the results for the
identical nanostructures made of 4H and 6H SiC polytypes, we demonstrate the
interplay of localized surface phonon polaritons with zone-folded weak phonon
modes of the anisotropic crystal. Tuning the monopole mode in and out of the
region where the zone-folded phonon is excited in 6H-SiC, we observe a
prominent increase of the already monopole-enhanced SHG output when the two
modes are coupled. Envisioning this interplay as one of the showcase features
of mid-infrared nonlinear nanophononics, we discuss its prospects for the
effective engineering of nonlinear-optical materials with desired properties in
the infrared spectral range.Comment: 16 pages, 3 figure
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