Recent advancements in nanofabrication technology have allowed for the implementation of nanostructures smaller than the wavelength of light on photonic chips. Integrating mature photonic waveguide technologies with concepts derived from nanophotonics offers exciting possibilities for achieving unparalleled manipulation of guided light waves. Nevertheless, the task of creating novel functionalities while maintaining efficiency and compatibility with existing technology poses a major challenge in the field of on-chip nanophotonics. Here, we introduce a new type of silicon-based optical meta-waveguide operating in the telecom spectral range. Our waveguides comprise a chain of Mie-resonant silicon nano resonators designed to exhibit nearly exclusively forward-scattering characteristics. This yields unique optical properties, including a large transmission gain and efficiently suppressed backscattering even in the presence of strong perturbations. This is an unprecedented combination of characteristics for any photonic system supporting guided modes, thereby unlocking completely new opportunities for fundamental research as well as future applications.
Nanoparticles made of High Refractive Index (HRI) dielectric materials, such as Si, GaP, Ge or other semiconductor compounds have been proposed recently as an alternative to metals, driven by their low-losses and presence of magnetic response in spite of being non-magnetic materials. However, they are known to suffer relatively large losses and absence of magnetic response at optical frequencies. Here, we intend to show a brief overview of our recent research in light scattering by HRI dielectric nanostructures. In particular, we will show how the strong confinement of electromagnetic energy and the outstanding scattering efficiencies of these HRI dielectric structures make them promising candidates to act as basic units for the design of the next generation of nanoantennas that may be able to boost applications such as sensing, light directivity, optical switching, surface enhanced spectroscopies, all-dielectric metamaterials, or non linear phenomena, such as third harmonic generation
Subwavelength metallic nanoparticles have been proposed for optimizing efficiency of current solar cells. However, their inherent ohmic losses limit their performance. High Refractive Index dielectric particles have been suggested as an alternative to metallic ones due to their low-losses in the visible and near infrared spectral regions and also to their magnetic response. The directionality properties that arise from the coherence effects between electric and magnetic resonances, make them very attractive for redirecting the incident radiation. In this work, we analyze the Scattering Directionality Conditions of a symmetric dimer made of High Refractive Index dielectric particles as a function of the gap. We demonstrate that, by using a dimer, it is possible to find, in the dipolar regime, two spectral regions where the incident radiation is redirected in the forward direction. They correspond to the Zero-Backward condition (also observed for isolated particles) and to a “near Zero-Backward” condition. The last would correspond to a “rotation” of the near Zero-Forward condition as a consequence of the interaction effects between the dimer components. The proposed scattering unit could constitute a new block for building more complex systems for applications in optical communications, light guiding and solar energy harvesting devices.
We analyze the effect of contaminants on the quadrupolar magnetic, dipolar electric and dipolar magnetic resonances of silicon nanoparticles (NPs) by considering the spectral evolution of the linear polarization degree at right angle scattering configuration, PL(90°). From an optical point of view, a decrease in the purity of silicon nanoparticles due to the presence of contaminants impacts the NP effective refractive index. We study this effect for a silicon nanosphere of radius 200 nm embedded in different media. The weakness of the resonances induced on the PL(90°) spectrum because of the lack of purity can be used to quantify the contamination of the material. In addition, it is shown that Kerker conditions also suffer from a spectral shift, which is quantified as a function of material purity.
Plasmonics in the UV-range constitutes a new challenge due to the increasing demand to detect, identify and destroy biological toxins, enhance biological imaging, and characterize semiconductor devices at the nanometer scale. Silver and aluminum have an efficient plasmonic performance in the near UV region, but oxidation reduces its performance in this range. Recent studies point out rhodium as one of the most promising metals for this purpose: it has a good plasmonic response in the UV and, as gold in the visible, it presents a low tendency to oxidation. Moreover, its easy fabrication through chemical means and its potential for photocatalytic applications, makes this material very attractive for building plasmonic tools in the UV. In this work, we will show an overview of our recent collaborative research with rhodium nanocubes (NC) for Plasmonics in the UV.
Recent studies show that the spectral behaviour of localized surface plasmon resonances (LPSRs) in metallic nanoparticles suffer from both a redshift and a broadening in the transition from the far- to the near-field regimes. An interpretation of this effect was given in terms of the evanescent and propagating components of the angular spectrum representation of the radiated field. Due to the increasing interest awakened by magnetodielectric materials as a both low-loss material option for nanotechnology applications, and also for their particular scattering properties, here we study the spectral response of a magnetodielectric nanoparticle as a basic element of a dielectric nano-antenna. This study is made by analyzing the changes suffered by the scattered electromagnetic field when propagating from the surface of this dielectric nanostructure to the far-zone in terms of propagating and evanescent plane wave components of the radiated fields.
The spectral evolution of the degree of linear polarization (PL) at a scattering angle of 90° is studied numerically for high refractive index (HRI) dielectric spherical nanoparticles. The behaviour of PL(90°) is analyzed as a function of the refractive index of the surrounding medium and the particle radius. We focus on the spectral region where both electric and magnetic resonances of order not higher than two are located for various semiconductor materials with low absorption. The spectral behavior of PL(90°) has only a small, linear dependence on nanoparticle size R. This weak dependence makes it experimentally feasible to perform real-time retrievals of both the refractive index of the external medium and the NP size R. From an industrial point of view, pure materials are nonrealistic, since they can only be provided under certain conditions. For this reason, we also study the effect of contaminants on the resonances of silicon NPs by considering the spectral evolution of PL(90°).
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