123 research outputs found
Broadband Transient Response and Wavelength-Tunable Photoacoustics in Plasmonic Hetero-nanoparticles
Optomechanical manipulation with hyperbolic metasurfaces
Auxiliary nanostructures introduce additional flexibility into optomechanical
manipulation schemes. Metamaterials and metasurfaces capable to control
electromagnetic interactions at the near-field regions are especially
beneficial for achieving improved spatial localization of particles, reducing
laser powers required for trapping, and for tailoring directivity of optical
forces. Here, optical forces acting on small particles situated next to
anisotropic substrates, are investigated. A special class of hyperbolic
metasurfaces is considered in details and is shown to be beneficial for
achieving strong optical pulling forces in a broad spectral range. Spectral
decomposition of the Green functions enables identifying contributions of
different interaction channels and underlines the importance of the hyperbolic
dispersion regime, which plays the key role in optomechanical interactions.
Homogenised model of the hyperbolic metasurface is compared to its
metal-dielectric multilayer realizations and is shown to predict the
optomechanical behaviour under certain conditions related to composition of the
top layer of the structure and its periodicity. Optomechanical metasurfaces
open a venue for future fundamental investigations and a range of practical
applications, where accurate control over mechanical motion of small objects is
required
Purcell effect in Hyperbolic Metamaterial Resonators
The radiation dynamics of optical emitters can be manipulated by properly
designed material structures providing high local density of photonic states, a
phenomenon often referred to as the Purcell effect. Plasmonic nanorod
metamaterials with hyperbolic dispersion of electromagnetic modes are believed
to deliver a significant Purcell enhancement with both broadband and
non-resonant nature. Here, we have investigated finite-size cavities formed by
nanorod metamaterials and shown that the main mechanism of the Purcell effect
in these hyperbolic resonators originates from the cavity hyperbolic modes,
which in a microscopic description stem from the interacting cylindrical
surface plasmon modes of the finite number of nanorods forming the cavity. It
is found that emitters polarized perpendicular to the nanorods exhibit strong
decay rate enhancement, which is predominantly influenced by the rod length. We
demonstrate that this enhancement originates from Fabry-Perot modes of the
metamaterial cavity. The Purcell factors, delivered by those cavity modes,
reach several hundred, which is 4-5 times larger than those emerging at the
epsilon near zero transition frequencies. The effect of enhancement is less
pronounced for dipoles, polarized along the rods. Furthermore, it was shown
that the Purcell factor delivered by Fabry-Perot modes follows the dimension
parameters of the array, while the decay rate in the epsilon near-zero regime
is almost insensitive to geometry. The presented analysis shows a possibility
to engineer emitter properties in the structured metamaterials, addressing
their microscopic structure
Multimode hybrid gold-silicon nanoantennas for tailored nanoscale optical confinement
High-index dielectric nanoantennas, which provide an interplay between electric and magnetic modes, have been widely used as building blocks for a variety of devices and metasurfaces, both in linear and nonlinear regimes. Here, we investigate hybrid metal-semiconductor nanoantennas, consisting of a multimode silicon nanopillar core coated with a gold layer, that offer an enhanced degree of control over the mode selection and confinement, and emission of light on the nanoscale exploiting high-order electric and magnetic resonances. Cathodoluminescence spectra revealed a multitude of resonant modes supported by the nanoantennas due to hybridization of the Mie resonances of the core and the plasmonic resonances of the shell. Eigenmode analysis revealed the modes that exhibit enhanced field localization at the gold interface, together with high confinement within the nanopillar volume. Consequently, this architecture provides a flexible means of engineering nanoscale components with tailored optical modes and field confinement for a plethora of applications, including sensing, hot-electron photodetection and nanophotonics with cylindrical vector beams.Peer ReviewedPostprint (published version
Optically-programmable nonlinear photonic component for dielectric-loaded plasmonic circuitry
We demonstrate both experimentally and numerically a compact and efficient, optically tuneable plasmonic component utilizing a surface plasmon polariton ring resonator with nonlinearity based on trans-cis isomerization in a polymer material. We observe more than 3-fold change between high and low transmission states of the device at milliwatt control powers (?100 W/cm2 by intensity), with the performance limited by switching speed of the material. Such plasmonic components can be employed in optically programmable and reconfigurable integrated photonic circuitry
- …