Conformal transformation in bowtie nanoantennas and nanocavities: unveiling hidden symmetries

In this work, bowtie nanoantennas and nanocavities are analyzed using the conformal transformation technique. Their performance is studied in terms of the non-radiative Purcell enhancement and self-induced optical forces experienced by quantum emitters. It is demonstrated how these two geometrically different plasmonic nanoparticles can share the same non-radiative Purcell spectra. This hidden symmetric response is unveiled by properly applying the conformal transformation technique, demonstrating that both nanoparticles share the same transformed geometry

Impact of plasmonic bowtie nanoantennas and nanocavities on the dynamics of nearby nanoemitters

Metallic nanoparticles exert a strong influence on the electrodynamics and mechanical dynamics of nanoemitters in their vicinity. Transformation optics can provide analytical descriptions and physical insight on these scenarios. As a case of study, we discuss the use of conformal transformation to understand the nonradiative Purcell enhancement and the optical forces experienced by nanoemitters nearby bowtie nanocavities and nanoantennas

Zoned near-zero refractive index fishnet lens antenna: Steering millimeter waves

The following article appeared in Pacheco-Pena, V., Orazbayev, B., Beaskoetxea, U., Beruete, M., & Navarro-Cia, M. (n.d). Zoned near-zero refractive index fishnet lens antenna: Steering millimeter waves. Journal Of Applied Physics, 115(12), and may be found at http://dx.doi.org/10.1063/1.4869436.A zoned fishnet metamaterial lens is designed, fabricated, and experimentally demonstrated at millimeter wavelengths to work as a negative near-zero refractive index lens suitable for compact lens antenna configurations. At the design frequency f=56.7GHz (wavelength = 5.29 mm), the zoned fishnet metamaterial lens, designed to have a focal length FL= 9 wavelengths, exhibits a refractive index n = 0.25. The focusing performance of the diffractive optical element is briefly compared with that of a non-zoned fishnet metamaterial lens and an isotropic homogeneous zoned lens made of a material with the same refractive index. Experimental and numerically-computed radiation diagrams of the fabricated zoned lens are presented and compared in detail with that of a simulated non-zoned lens. Simulation and experimental results are in good agreement, demonstrating an enhancement generated by the zoned lens of 10.7 dB, corresponding to a gain of 12.26 dB. Moreover, beam steering capability of the structure by shifting the feeder on the xz-plane is demonstrated.This work was supported in part by the Spanish Government under contract Consolider Engineering Metamaterials CSD2008-00066 and Contract No. TEC2011- 28664-C02-01. V.P.-P. is sponsored by Spanish Ministerio de Educacion, Cultura y Deporte under Grant No. FPU AP- 2012-3796. B.O. is sponsored by Spanish Ministerio de Economıa y Competitividad under Grant No. FPI BES-2012- 054909. M.B. is sponsored by the Spanish Government via RYC-2011-08221. M. N.-C. is supported by the Imperial College Junior Research Fellowship

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations

Understanding Bowtie Nanoantennas Excited by a Localized Emitter

A full analytical description of a bowtie nanoantenna excited by a localized emitter is presented using the transformation electromagnetic technique. By applying the conformal mapping, the bowtie nanoantenna is transformed into a periodic multi-parallel plate transmission line problem which can be easily evaluated analytically providing physical insight of the coupling between the dipole nanoemitter and the bowtie nanoantenna. The non-radiative Purcell enhancement spectrum is evaluated both analytically and numerically for different lengths, arm angles and metals, demonstrating a good agreement between both approaches. The method here presented fills the gap of the design techniques for optical nanoantennas