Author
Marco Finazzi
Other affiliations: Leonardo, Sapienza University of Rome, University of Paris ...read more
Bio: Marco Finazzi is an academic researcher from Polytechnic University of Milan. The author has contributed to research in topics: Second-harmonic generation & X-ray magnetic circular dichroism. The author has an hindex of 36, co-authored 302 publications receiving 5405 citations. Previous affiliations of Marco Finazzi include Leonardo & Sapienza University of Rome.
Papers published on a yearly basis
Papers
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TL;DR: Doubly-resonant single-crystalline gold nanostructures with no axial symmetry displaying spatial mode overlap at both the excitation and second harmonic wavelengths are described, enabling a second harmonic photon yield higher than 3 × 10(6) photons per second.
Abstract: An asymmetric plasmonic nanoantenna featuring a double resonant mode that overlaps with both the excitation fundamental wavelength and the second harmonic emission displays a remarkably large nonlinear coefficient for second harmonic generation.
438 citations
TL;DR: The creation and real-space observation of magnetic structures with well-defined topological properties and a lateral size as low as about 150 nm are reported, generated in a thin ferrimagnetic film by ultrashort single optical laser pulses.
Abstract: We report the creation and real-space observation of magnetic structures with well-defined topological properties and a lateral size as low as about 150 nm. They are generated in a thin ferrimagnetic film by ultrashort single optical laser pulses. Thanks to their topological properties, such structures can be classified as Skyrmions of a particular type that does not require an externally applied magnetic field for stabilization. Besides Skyrmions, we are able to generate magnetic features with topological characteristics that can be tuned by changing the laser fluence. The stability of such features is accounted for by an analytical model based on the interplay between the exchange and the magnetic dipole-dipole interactions. Skyrmions [1] are particlelike solutions of wave equations characterized by a topological index which is conserved in time and plays the important role of a quantum number for particle states in the corresponding field theory. One of the most interesting characteristics of such topological states of matter resides in the robustness that they hold with respect to perturbations and disorder. In magnetic materials, Skyrmions emerge as solitonlike excitations that cannot be traced back to the ground ferromagnetic state by continuous deformations of the local
285 citations
TL;DR: The cross antenna is able to convert propagating fields of any polarization state into correspondingly polarized, localized, and enhanced fields and vice versa and opens the road towards the control of light-matter interactions based on polarized light as well as the analysis of polarized fields on the nanometer scale.
Abstract: We propose a novel cross resonant optical antenna consisting of two perpendicular nanosized gold dipole antennas with a common feed gap. We demonstrate that the cross antenna is able to convert propagating fields of any polarization state into correspondingly polarized, localized, and enhanced fields and vice versa. The cross antenna structure therefore opens the road towards the control of light-matter interactions based on polarized light as well as the analysis of polarized fields on the nanometer scale.
195 citations
TL;DR: In this article, the second harmonic generation from AlGaAs nanocylinders of 400 nm height and varying radius was measured with femtosecond pulses delivered at 1554nm wavelength.
Abstract: We demonstrate monolithic aluminum gallium arsenide (AlGaAs) optical nanoantennas. Using a selective oxidation technique, we fabricated epitaxial semiconductor nanocylinders on an aluminum oxide substrate. Second harmonic generation from AlGaAs nanocylinders of 400 nm height and varying radius pumped with femtosecond pulses delivered at 1554-nm wavelength has been measured, revealing a peak conversion efficiency exceeding 10−5 for nanocylinders with an optimized geometry.
162 citations
TL;DR: Second harmonic generation from AlGaAs nanocylinders of 400 nm height and varying radius pumped with femtosecond pulses delivered at 1554-nm wavelength has been measured, revealing a peak conversion efficiency exceeding 10-5 for nanocyleinders with an optimized geometry.
Abstract: We demonstrate monolithic aluminum gallium arsenide (AlGaAs) optical anoantennas. Using a selective oxidation technique, we fabricate such epitaxial semiconductor nanoparticles on an aluminum oxide substrate. Second harmonic generation from an AlGaAs nanocylinder of height h=400 nm and varying radius pumped with femtosecond pulses delivered at 1554-nm wavelength has been measured, revealing a peak conversion efficiency exceeding 10-5 for nanocylinders with an otpimized geometry.
134 citations
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TL;DR: In this article, a two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint phase discontinuities on propagating light as it traverses the interface between two media.
Abstract: Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat’s principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.
6,763 citations
TL;DR: This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam.
Abstract: Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.
4,613 citations
TL;DR: From this description, potential applications of skyrmions as information carriers in magnetic information storage and processing devices are envisaged.
Abstract: Magnetic skyrmions are particle-like nanometre-sized spin textures of topological origin found in several magnetic materials, and are characterized by a long lifetime. Skyrmions have been observed both by means of neutron scattering in momentum space and microscopy techniques in real space, and their properties include novel Hall effects, current-driven motion with ultralow current density and multiferroic behaviour. These properties can be understood from a unified viewpoint, namely the emergent electromagnetism associated with the non-coplanar spin structure of skyrmions. From this description, potential applications of skyrmions as information carriers in magnetic information storage and processing devices are envisaged.
3,132 citations
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TL;DR: Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa as mentioned in this paper, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing.
Abstract: Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa. They enable the control and manipulation of optical fields at the nanometre scale, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing. Although many of the properties and parameters of optical antennas are similar to their radiowave and microwave counterparts, they have important differences resulting from their small size and the resonant properties of metal nanostructures. This Review summarizes the physical properties of optical antennas, provides a summary of some of the most important recent developments in the field, discusses the potential applications and identifies the future challenges and opportunities.
2,557 citations
TL;DR: How high-index dielectric nanoparticles can offer a substitute for plasmonic nanoparticle structures, providing a highly flexible and low-loss route to the manipulation of light at the nanoscale is reviewed.
Abstract: The resonant modes of plasmonic nanoparticle structures made of gold or silver endow them with an ability to manipulate light at the nanoscale. However, owing to the high light losses caused by metals at optical wavelengths, only a small fraction of plasmonics applications have been realized. Kuznetsov et al. review how high-index dielectric nanoparticles can offer a substitute for these metals, providing a highly flexible and low-loss route to the manipulation of light at the nanoscale.
Science , this issue p. [10.1126/science.aag2472][1]
[1]: /lookup/doi/10.1126/science.aag2472
2,161 citations