Imperial College London

DrEmanueleGaliffi

Faculty of Natural SciencesDepartment of Physics

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emanuele.galiffi12 CV

 
 
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Location

 

Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

26 results found

Matson J, Wasserroth S, Ni X, Obst M, Diaz-Granados K, Carini G, Renzi EM, Galiffi E, Folland TG, Eng LM, Michael Klopf J, Mastel S, Armster S, Gambin V, Wolf M, Kehr SC, Alu A, Paarmann A, Caldwell JDet al., 2023, Controlling the propagation asymmetry of hyperbolic shear polaritons in beta-gallium oxide, NATURE COMMUNICATIONS, Vol: 14

Journal article

Galiffi E, Xu G, Yin S, Moussa H, Ra'di Y, Alu Aet al., 2023, Broadband coherent wave control through photonic collisions at time interfaces, NATURE PHYSICS, ISSN: 1745-2473

Journal article

Moussa H, Xu G, Yin S, Galiffi E, Ra'di Y, Alu Aet al., 2023, Observation of temporal reflection and broadband frequency translation at photonic time interfaces, NATURE PHYSICS, Vol: 19, Pages: 863-+, ISSN: 1745-2473

Journal article

Ni X, Carini G, Ma W, Renzi EM, Galiffi E, Wasserroth S, Wolf M, Li P, Paarmann A, Alu Aet al., 2023, Observation of directional leaky polaritons at anisotropic crystal interfaces, NATURE COMMUNICATIONS, Vol: 14

Journal article

Sapienza R, Pendry J, Maier S, Vezzoli S, Tirole R, Galiffi E, Dranczewski J, Attavar Tet al., 2022, Saturable time-varying mirror based on an epsilon-near-zero material, Physical Review Applied, Vol: 18, ISSN: 2331-7019

We report a switchable time-varying mirror, composed of an indium-tin-oxide–gold bilayer, displaying a tenfold modulation of reflectivity (ΔR≈0.6), which saturates for a driving-pump intensity Ipump≈100GW/cm2. Upon interacting with the saturated time-varying mirror, the frequency content of a reflected pulse is extended up to 31 THz, well beyond the pump spectral content (2.8 THz). We interpret the spectral broadening as a progressive shortening of the mirror rise time from 110 fs to below 30 fs with increasing pump power, which is confirmed by four-wave-mixing experiments and partially captured by a linear time-varying model of the mirror. A temporal response unbounded by the pump bandwidth enables applications for spectral manipulation from time-varying systems with impact for communication networks, optical switching, and computing.

Journal article

Galiffi E, Yin S, Alu A, 2022, Tapered photonic switching, NANOPHOTONICS, Vol: 11, Pages: 3575-3581, ISSN: 2192-8606

Journal article

Galiffi E, Huidobro PA, Pendry JB, 2022, Publisher Correction: An Archimedes’ screw for light, Nature Communications, Vol: 13, Pages: 1-1, ISSN: 2041-1723

Journal article

Tsai Y-W, Wang Y-T, Galiffi E, Alu A, Yen T-Jet al., 2022, Surface-wave coupling in double Floquet sheets supporting phased temporal Wood anomalies, NANOPHOTONICS, Vol: 11, Pages: 3509-3517, ISSN: 2192-8606

Journal article

Galiffi E, Huidobro PA, Pendry J, 2022, An Archimedes' screw for light, Nature Communications, Vol: 13, Pages: 1-8, ISSN: 2041-1723

An Archimedes’ Screw captures water, feeding energy into it by lifting it to a higher level. We introduce the first instance of an optical Archimedes’ Screw, and demonstrate how this system is capable of capturing light, dragging it and amplifying it. We unveil new exact analytic solutions to Maxwell’s Equations for a wide family of chiral space-time media, and show their potential to achieve chirally selective amplification within widely tunable parity-time-broken phases. Our work, which may be readily implemented via pump-probe experiments with circularly polarized beams, opens a new direction in the physics of time-varying media by merging the rising field of space-time metamaterials and that of chiral systems, and offers a new playground for topological and non-Hermitian photonics, with potential applications to chiral spectroscopy and sensing.

Journal article

Galiffi E, Huidobro P, Pendry J, 2022, An Archimedes' screw for light, Publisher: ArXiv

An Archimedes' Screw captures water, feeding energy into it by lifting it to a higher level. We introduce the first instance of an optical Archimedes' Screw, and demonstrate how this system is capable of capturing light, dragging it and amplifying it. We unveil new exact analytic solutions to Maxwell's Equations for a wide family of chiral space-time media, and show their potential to achieve chirally selective amplification within widely tunable parity-time-broken phases. Our work, which may be readily implemented via pump-probe experiments with circularly polarized beams, opens a new direction in the physics of time-varying media by merging the rising field of space-time metamaterials and that of chiral systems, and offers a new playground for topological and non-Hermitian photonics, with potential applications to chiral spectroscopy and sensing.

Working paper

Galiffi E, Tirole R, Yin S, Li H, Vezzoli S, Huidobro PA, Silveirinha MG, Sapienza R, Alu A, Pendry JBet al., 2022, Photonics of time-varying media, ADVANCED PHOTONICS, Vol: 4

Journal article

Pendry J, Galiffi E, Huidobro P, 2021, Gain in time dependent media - a new mechanism, Journal of the Optical Society of America B, Vol: 38, Pages: 3360-3366, ISSN: 0740-3224

Time dependent systems do not in general conserve energy invalidating much of thetheory developed for static systems and turning our intuition on its head. This is particularlyacute in luminal space time crystals where the structure moves at or close to the velocity oflight. Conventional Bloch wave theory no longer applies, energy grows exponentially withtime, and a new perspective is required to understand the phenomenology. In this letter weidentify a new mechanism for amplification: the compression of lines of force that arenevertheless conserved in number.

Journal article

Li H, Yin S, Galiffi E, Alù Aet al., 2021, Temporal Parity-Time Symmetry for Extreme Energy Transformations., Phys Rev Lett, Vol: 127

Temporal interfaces introduced by abrupt switching of the constitutive parameters of unbounded media enable unusual wave phenomena. So far, their explorations have been mostly limited to lossless media. Yet, non-Hermitian phenomena leveraging material loss and gain, and their balanced combination in parity-time (PT)-symmetric systems, have been opening new vistas in photonics. Here, we unveil the role that temporal interfaces offer in non-Hermitian physics, introducing the dual of PT symmetry for temporal boundaries. Our findings reveal unexplored interference mechanisms enabling extreme energy manipulation, and open new scenarios for time-switched metamaterials, connecting them with the broad opportunities offered by non-Hermitian phenomena.

Journal article

Huidobro et al, 2021, Correction for Huidobro et al., Fresnel drag in space–time-modulated metamaterials, Proceedings of the National Academy of Sciences, Vol: 118, Pages: 1-1, ISSN: 0027-8424

Journal article

Pendry JB, Galiffi E, Huidobro PA, 2021, Gain mechanism in time-dependent media, OPTICA, Vol: 8, Pages: 636-637, ISSN: 2334-2536

Journal article

Galiffi E, Wang Y-T, Lim Z, Pendry JB, Alu A, Huidobro PAet al., 2020, Wood Anomalies and Surface-Wave Excitation with a Time Grating, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007

Journal article

Lu L, Galiffi E, Ding K, Dong T, Ma X, Pendry JBet al., 2020, Plasmon Localization Assisted by Conformal Symmetry, ACS Photonics, ISSN: 2330-4022

Journal article

Yang F, Galiffi E, Huidobro PA, Pendry Jet al., 2020, Nonlocal effects in plasmonic metasurfaces with almost touching surfaces, PHYSICAL REVIEW B, Vol: 101, ISSN: 2469-9950

Journal article

Galiffi E, Arroyo Huidobro P, Goncalves PAD, Mortensen NA, Pendry Jet al., 2020, Probing graphene’s nonlocality with singular metasurfaces, Nanophotonics, Vol: 9, Pages: 309-316, ISSN: 2192-8606

Singular graphene metasurfaces, conductivity gratings realized by periodically suppressing the local doping level of a graphene sheet, were recently proposed to efficiently harvest THz light and couple it to surface plasmons over broad absorption bands, thereby achieving remarkably high field enhancement. However, the large momentum wavevectors thus attained are sensitive to the nonlocal behavior of the underlying electron liquid. Here, we extend the theory of singular graphene metasurfaces to account for the full nonlocal optical response of graphene and discuss the resulting impact on the plasmon resonance spectrum. Finally, we propose a simple local-analogue model that is able to reproduce the effect of nonlocality in local-response calculations by introducing a constant conductivity offset, which could prove a valuable tool in the modeling of more complex experimental graphene-based platforms.

Journal article

Galiffi E, Huidobro PA, Goncalves PAD, Mortensen NA, Pendry JBet al., 2019, Probing graphene's nonlocality with singular metasurfaces, Publisher: arXiv

Singular graphene metasurfaces, conductivity gratings realized by periodically suppressing the local doping level of a graphene sheet, have recently been proposed to efficiently harvest THz light and couple it to surface plasmons over broad absorption bands, achieving remarkably high field enhancement. However, the large momentum wavevectors thus attained are sensitive to the nonlocal behaviour of the underlying electron liquid. Here, we extend the theory of singular graphene metasurfaces to account for the full nonlocal optical response of graphene and discuss the resulting impact on the plasmon resonance spectrum. Finally, we propose a simple local analogue model that is able to reproduce the effect of nonlocality in local-response calculations by introducing a constant conductivity offset, which could prove a valuable tool in the modelling of more complex experimental graphene-based platforms.

Working paper

Huidobro PA, Galiffi E, Guenneau S, Craster RV, Pendry JBet al., 2019, Fresnel drag in space-time-modulated metamaterials, Publisher: arXiv

A moving medium drags light along with it as measured by Fizeau and explained by Einstein's theory of special relativity. Here we show that the same effect can be obtained in a situation where there is no physical motion of the medium. Modulations of both the permittivity and permeability, phased in space and time in the form of travelling waves, are the basis of our model. Space-time metamaterials are represented by effective bianisotropic parameters, which can in turn be mapped to a moving homogeneous medium. Hence these metamaterials mimic a relativistic effect without the need for any actual material motion. We discuss how both the permittivity and permeability need to be modulated in order to achieve these effects, and we present an equivalent transmission line model.

Working paper

Galiffi E, Huidobro PA, Pendry JB, 2019, Broadband nonreciprocal THz amplification in luminal graphene metasurfaces, Publisher: arXiv

Time has emerged as a new degree of freedom for metamaterials, promising newpathways in wave control. However, electromagnetism suffers from limitations inthe modulation speed of material parameters. Here we argue that theselimitations can be circumvented by introducing a traveling-wave refractiveindex modulation, with the same phase velocity of the waves. We show how theconcept of "luminal grating" can yield giant nonreciprocity, achieve efficientone-way amplification, pulse compression and frequency up-conversion, proposinga realistic implementation in double-layer graphene.

Working paper

Galiffi E, Pendry J, Arroyo Huidobro P, 2019, Singular Graphene Metasurfaces, EPJ Applied Metamaterials, Vol: 6, ISSN: 2272-2394

The spatial tunability of the electron density in graphene enables the dynamic engineering of metasurfaces in the form of conductivity gratings, which can bridge the momentum gap between incident radiation and surface plasmons. Here, we discuss singular graphene metasurfaces, whose conductivity is strongly suppressed at the grating valleys. By analytically characterising their plasmonic response via transformation optics, we first review the physical principles underlying these structures, which were recently found to exhibit broadband, tunable THz absorption. We characterise the spectrum with different common substrates and then move to study in further detail how conductivity gratings may be finely tuned by placing an array of charged gold nanowires at sub-micron distance from the graphene.

Journal article

Galiffi E, Pendry JB, Huidobro PA, 2018, Broadband tunable THz absorption with singular graphene metasurfaces, ACS Nano, Vol: 12, Pages: 1006-1013, ISSN: 1936-0851

By exploiting singular spatial modulations of the graphene conductivity, we design a broadband, tunable THz absorber whose efficiency approaches the theoretical upper bound for a wide absorption band with a fractional bandwidth of 185%. Strong field enhancement is exhibited by the modes of this extended structure, which is able to excite a wealth of high-order surface plasmons, enabling deeply subwavelength focusing of incident THz radiation. Previous studies have shown that the conductivity can be modulated at GHz frequencies, which might lead to the development of efficient high-speed broadband switching by an atomically thin layer.

Journal article

Pendry JB, Huidobro PA, Luo Y, Galiffi Eet al., 2017, Compacted dimensions and singular plasmonic surfaces, Science, Vol: 358, Pages: 915-917, ISSN: 0036-8075

In advanced field theories, there can be more than four dimensions to space, the excess dimensions described as compacted and unobservable on everyday length scales. We report a simple model, unconnected to field theory, for a compacted dimension realized in a metallic metasurface periodically structured in the form of a grating comprising a series of singularities. An extra dimension of the grating is hidden, and the surface plasmon excitations, though localized at the surface, are characterized by three wave vectors rather than the two of typical two-dimensional metal grating. We propose an experimental realization in a doped graphene layer.

Journal article

Galiffi E, Suenderhauf C, DeKieviet M, Wimberger Set al., 2017, Two-dimensional simulation of quantum reflection, Journal of Physics B: Atomic, Molecular and Optical Physics, Vol: 50, ISSN: 0953-4075

A propagation method for the scattering of a quantum wave packet from a potential surface is presented. It is used to model the quantum reflection of single atoms from a corrugated (metallic) surface. Our numerical procedure works well in two spatial dimensions requiring only reasonable amounts of memory and computing time. The effects of the surface corrugation on the reflectivity are investigated via simulations with a paradigm potential. These indicate that our approach should allow for future tests of realistic, effective potentials obtained from theory in a quantitative comparison to experimental data.

Journal article

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