Directive antenna nanocoupler to plasmonic gap waveguides

Research Square (Research Square), 2023

An array of metallic nanoparticles can diffract or concentrate the incident electromagnetic wave and hence behaves as an antenna. In this paper, the effects of inner sub-wavelength structure of nanoparticles is studied on the directivity of the plasmonic nanoantenna which is coated on the output of a waveguide. The results show that structured nanoantennas can improve the directivity of the antenna due to the hybridization mechanism. The resuls may be useful for designing and fabricateing directive optical fibers endcaps.

Physical Review B, 2008

For their capability to localize and redirect electromagnetic field, metal nanoparticles have been recently viewed as efficient nanoantenna operating in the optical regime. In this article, we experimentally investigated the optical responses of coupled gold antenna pairs and measured the critical parameters defining antenna characteristics: resonant frequencies and bandwidths, detuning and gains, and radiation patterns.

Nano Lett, 2009

Optics Letters, 2010

We propose a type of photonic-plasmonic antennas capable of focusing light into subwavelength focal point(s) at several wavelengths, which are formed by embedding conventional dimer gap or bow-tie nanoantennas into multiple-periodic gratings. Fano-type coupling between localized surface plasmon resonances of dimer antennas and photonic modes in the gratings adds new functionalities, including multiple-wavelength operation and controllable enhancement of the field intensity in the focal point. Multiple-wavelength operation of nanoantennas provides tremendous opportunities for broadband single-molecule fluorescence and Raman sensing, emission enhancement, and near-field imaging.

Nano Letters, 2014

We successfully demonstrate the plasmonic coupling between metal nanoantennas and individual GaAs nanowires (NWs). In particular, by using dark-field scattering and second harmonic excitation spectroscopy in partnership with analytical and full-vector FDTD modeling, we demonstrate controlled electromagnetic coupling between individual NWs and plasmonic nanoantennas with gap sizes varied between 90 and 500 nm. The significant electric field enhancement values (up to 20×) achieved inside the NWnanoantennas gap regions allowed us to tailor the nonlinear optical response of NWs by engineering the plasmonic near-field coupling regime. These findings represent an initial step toward the development of coupled metal−semiconductor resonant nanostructures for the realization of next generation solar cells, detectors, and nonlinear optical devices with reduced footprints and energy consumption.

Cornell University - arXiv, 2022

In this paper we propose and demonstrate single subwavelength hybrid dielectricplasmonic optical nanoantennas coupled to localised quantum dot emitters that constitute efficient and bright unidirectional photon sources under optical pumping. To 1 achieve this, we devised a silicon nanoring sitting on a metallic (gold) mirror with a 10 nm gap in between, where an assembly of quantum dots is embedded. Such a structure supports both gap mode and (radiative) antenna mode resonances. We experimentally show that the assembly of quantum dots localised within the nanogap can efficiently couple to these two kind of modes, the resonant gap modes and the antenna modes, for the dual purpose of enhancing the absorption of the optical pump by the emitters, and for out-coupling the light into the far-field with high directionality. Moreover, almost independent control of the resonance spectral positions is achieved by simple tuning of geometrical parameters such as the ring outer and inner diameters, which is not possible with other, simpler, particle-on-mirror nanoantennas. Using the proposed architecture, we obtain average fluorescence enhancement factors of the assembly of emitters up to 654× folds together with a high radiation efficiency, and a directional emission of the photoluminescence into a cone of ±17°in the direction normal to the sample plane.

Physics Research International, 2012

The optical properties of plasmonic nanoantennas are investigated in detail using the finite integration technique (FIT). The validity of this technique is verified by comparison to the exact solution generalized Mie method (GMM). The influence of the geometrical parameters (antenna length, gap dimension, and shapes) on the antenna field enhancement and spectral response is discussed. Localized surface plasmon resonances of Au (gold) dimers nanospheres, bowtie, and aperture bowtie nanoantennas are modeled. The enhanced field is equivalent to a strong light spot which can lead to the resolution improvement of the microscopy and optical lithography, thus increasing the optical data storage capacity. Furthermore, the sensitivity of the antennas to index changes of the environment and substrate is investigated in detail for biosensing applications. We confirm that our approach yields an exact correspondence with GMM theory for Au dimers nanospheres at gap dimensions 5 nm and 10 nm but g...

Optics Express, 2012

We study in detail a novel type of optical nanoantennas made of high-permittivity low-loss dielectric particles. In addition to the electric resonances, the dielectric particles exhibit very strong magnetic resonances at the nanoscale, that can be employed in the Yagi-Uda geometry for creating highly efficient optical nanoantennas. By comparing plasmonic and dielectric nanoantennas, we demonstrate that all-dielectric nanoantennas may exhibit better radiation efficiency also allowing more compact design.

ACS Photonics, 2017

Electrically-driven optical antennas can serve as compact sources of electromagnetic radiation operating at optical frequencies. In the most widely explored configurations, the radiation is generated by electrons tunneling between metallic parts of the structure when a bias voltage is applied across the tunneling gap. Rather than relying on an inherently inefficient inelastic light emission in the gap, we suggest to use a ballistic nanoconstriction as the feed element of an optical antenna supporting plasmonic modes. We discuss the underlying mechanisms responsible for the optical emission, and show that with such a nanoscale contact, one can reach quantum efficiency orders of magnitude larger than with standard light-emitting tunneling structures.

Journal of Nanophotonics, 2011