Publications
468 results found
Tirole R, Attavar T, Dranczewski J, et al., 2021, Time Diffraction in an Epsilon-Near-Zero Metasurface, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
Pendry JB, Galiffi E, Huidobro PA, 2020, A new mechanism for gain in time dependent media
Time dependent systems do not in general conserve energy invalidating much ofthe theory developed for static systems and turning our intuition on its head.This is particularly acute in luminal space time crystals where the structuremoves at or close to the velocity of light. Conventional Bloch wave theory nolonger applies, energy grows exponentially with time, and a new perspective isrequired to understand the phenomenology. In this letter we identify a newmechanism for amplification: the compression of lines of force that arenevertheless conserved in number.
Galiffi E, Wang Y-T, Lim Z, et al., 2020, Wood Anomalies and Surface-Wave Excitation with a Time Grating, PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007
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- Citations: 38
Yang F, Huidobro PA, Pendry JB, 2020, Electron Energy Loss Spectroscopy of Singular Plasmonic Metasurfaces, LASER & PHOTONICS REVIEWS, Vol: 14, ISSN: 1863-8880
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- Citations: 2
Yang F, Ding K, Pendry J, 2020, Shrinking the surface plasmon, Nanophotonics, Vol: 10, Pages: 545-548, ISSN: 2192-8606
Surface plasmons at an interface between dielectric and metal regions can in theory be made arbitrarily compact normal to the interface by introducing extreme anisotropy in the material parameters. We propose a metamaterial structure comprising a square array of gold cylinders and tune the filling factor to achieve the material parameters we seek. Theory is compared to a simulation wherein the unit cell dimensions of the metamaterial are shown to be the limiting factor in the degree of localisation achieved.
Yang F, Ma S, Ding K, et al., 2020, Continuous topological transition from metal to dielectric, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 117, Pages: 16739-16742, ISSN: 0027-8424
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- Citations: 3
Sikdar D, Pendry JB, Kornyshev AA, 2020, Nanoparticle meta-grid for enhanced light extraction from light-emitting devices., Light Sci Appl, Vol: 9
Based on a developed theory, we show that introducing a meta-grid of sub-wavelength-sized plasmonic nanoparticles (NPs) into existing semiconductor light-emitting-devices (LEDs) can lead to enhanced transmission of light across the LED-chip/encapsulant interface. This results from destructive interference between light reflected from the chip/encapsulant interface and light reflected by the NP meta-grid, which conspicuously increase the efficiency of light extraction from LEDs. The "meta-grid", should be inserted on top of a conventional LED chip within its usual encapsulating packaging. As described by the theory, the nanoparticle composition, size, interparticle spacing, and distance from the LED-chip surface can be tailored to facilitate maximal transmission of light emitted from the chip into its encapsulating layer by reducing the Fresnel loss. The analysis shows that transmission across a typical LED-chip/encapsulant interface at the peak emission wavelength can be boosted up to ~99%, which is otherwise mere ~84% at normal incidence. The scheme could provide improved transmission within the photon escape cone over the entire emission spectrum of an LED. This would benefit energy saving, in addition to increasing the lifetime of LEDs by reducing heating. Potentially, the scheme will be easy to implement and adopt into existing semiconductor-device technologies, and it can be used separately or in conjunction with other methods for mitigating the critical angle loss in LEDs.
Kornyshev A, Pendry J, Sikdar D, 2020, Nanoparticle meta-grid for enhanced light extraction from light emitting devices, Light: Science and Applications, Vol: 9, Pages: 1-11, ISSN: 2047-7538
Based on a developed theory, we show that introducing a meta-grid of sub-wavelength-sized plasmonic nanoparticles (NPs) into existing semiconductor light-emitting-devices (LEDs) can lead to enhanced transmission of light across the LED-chip/encapsulant interface. This results from destructive interference between light reflected from the chip/encapsulant interface and light reflected by the NP meta-grid, which conspicuously increase the efficiency of light extraction from LEDs. The “meta-grid”, should be inserted on top of a conventional LED chip within its usual encapsulating packaging. As described by the theory, the nanoparticle composition, size, interparticle spacing, and distance from the LED-chip surface can be tailored to facilitate maximal transmission of light emitted from the chip into its encapsulating layer by reducing the Fresnel loss. The analysis shows that transmission across a typical LED-chip/encapsulant interface at the peak emission wavelength can be boosted up to ~99%, which is otherwise mere ~84% at normal incidence. The scheme could provide improved transmission within the photon escape cone over the entire emission spectrum of an LED. This would benefit energy saving, in addition to increasing the lifetime of LEDs by reducing heating. Potentially, the scheme will be easy to implement and adopt into existing semiconductor-device technologies, and it can be used separately or in conjunction with other methods for mitigating the critical angle loss in LEDs.
Lu L, Galiffi E, Ding K, et al., 2020, Plasmon Localization Assisted by Conformal Symmetry, ACS Photonics, ISSN: 2330-4022
Yang F, Galiffi E, Huidobro PA, et al., 2020, Nonlocal effects in plasmonic metasurfaces with almost touching surfaces, PHYSICAL REVIEW B, Vol: 101, ISSN: 2469-9950
Galiffi E, Arroyo Huidobro P, Goncalves PAD, et 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.
Galiffi E, Huidobro PA, Goncalves PAD, et 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.
Huidobro PA, Galiffi E, Guenneau S, et 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.
Zhang Y, Luo Y, Pendry JB, et al., 2019, Transformation-Invariant Metamaterials, PHYSICAL REVIEW LETTERS, Vol: 123, ISSN: 0031-9007
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.
Yang F, Wang Y-T, Huidobro PA, et al., 2019, Nonlocal effects in singular plasmonic metasurfaces, Physical Review B, Vol: 99, ISSN: 2469-9950
A local model of the dielectric response of a metal predicts that singular surfaces, such as sharp-edged structures, have a continuous absorption spectrum and extreme concentration of energy at the singularity. Here, we show that nonlocality drastically alters this picture: The spectrum is now discrete and the energy concentration, though still substantial, is greatly reduced.
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.
Pendry JB, Huidobro PA, Ding K, 2019, Computing one-dimensional metasurfaces, Physical Review B, Vol: 99, ISSN: 2469-9950
We show that complex periodic metasurfaces can be simply represented by conformal transformations from the flat surface of a slab of material to a periodic grating leading to a methodology for computing their properties. Matrix equations are solved to give accurate solutions of Maxwell's equations with detailed derivations given in the Supplemental Material.
Zhang J, Pendry JB, Luo Y, 2019, Transformation optics from macroscopic to nanoscale regimes, ADVANCED PHOTONICS, Vol: 1
Zhang J, Pendry JB, Luo Y, 2019, Transformation optics from macroscopic to nanoscale regimes: a review, ADVANCED PHOTONICS, Vol: 1
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- Citations: 25
Zhang J, Pendry JBB, Luo Y, 2019, Transformation optics from macroscopic to nanoscale regimes, ADVANCED PHOTONICS, Vol: 1
Garnov SV, Dianov EM, Konov VI, et al., 2019, In memory of Viktor Georgievich Veselago, PHYSICS-USPEKHI, Vol: 62, Pages: 315-316, ISSN: 1063-7869
Yang F, Huidobro PA, Pendry JB, 2018, Transformation optics approach to singular metasurfaces, Physical Review B, Vol: 98, ISSN: 2469-9950
Surface plasmons dominate the optical response of metal surfaces, and their nature is controlled by surface geometry. Here we study metasurfaces containing singularities in the form of sharp edges and characterized by three quantum numbers despite the two-dimensional nature of the surface. We explore the nature of the plasmonic excitations, their ability to generate large concentrations of optical energy, and the transition from the discrete excitation spectrum of a nonsingular surface to the continuous spectrum of a singular metasurface.
McCall M, Pendry J, Galdi V, et al., 2018, Roadmap on transformation optics, Journal of Optics A: Pure and Applied Optics, Vol: 20, ISSN: 1464-4258
Transformation Optics asks Maxwell’s equations what kind of electromagnetic medium recreate some smooth deformation of space. The guiding principle is Einstein’s principle of covariance: that any physical theory must take the same form in any coordinate system. This requirement fixes very precisely the required electromagnetic medium.The impact of this insight cannot be overestimated. Many practitioners were used to thinking that only a few analytic solutions to Maxwell’s equations existed, such as the monochromatic plane wave in a homogeneous, isotropic medium. At a stroke, Transformation Optics increases that landscape from ‘few’ to ‘infinity’, and to each of the infinitude of analytic solutions dreamt up by the researcher, corresponds an electromagnetic medium capable of reproducing that solution precisely. The most striking example is the electromagnetic cloak, thought to be an unreachable dream of science fiction writers, but realised in the laboratory a few months after the papers proposing the possibility were published. But the practical challenges are considerable, requiring meta-media that are at once electrically and magnetically inhomogeneous and anisotropic. How far have we come since the first demonstrations over a decade ago? And what does the future hold? If the wizardry of perfect macroscopic optical invisibility still eludes us in practice, then what compromises still enable us to create interesting, useful, devices? While 3D cloaking remains a significant technical challenge, much progress has been made in 2-dimensions. Carpet cloaking, wherein an object is hidden under a surface that appears optically flat, relaxes the constraints of extreme electromagnetic parameters. Surface wave cloaking guides sub-wavelength surface waves, making uneven surfaces appear flat. Two dimensions is also the setting in which conformal and complex coordinate transformations are realisable, and the possibilities in this restr
Chen W-J, Hou B, Zhang Z-Q, et al., 2018, Metamaterials with index ellipsoids at arbitrary k-points, Nature Communications, Vol: 9, Pages: 1-10, ISSN: 2041-1723
Propagation behaviors of electromagnetic waves are governed by the equifrequency surface of the medium. Up to now, ordinary materials, including the medium exist in nature and the man-made metamaterials, always have an equifrequency surface (ellipsoid or hyperboloid) centered at zero k-point. Here we propose a new type of metamaterial possessing multiple index ellipsoids centered at arbitrary nonzero k-points. Their locations in momentum space are determined by the connectivity of a set of interpenetrating metallic scaffolds, whereas the group velocities of the modes are determined by the geometrical details. Such system is a new class of metamaterial whose properties arise from global connectivity and hence can have broadband functionality in applications such as negative refraction, orientation-dependent coupling effect, and cavity without walls, and they are fundamentally different from ordinary resonant metamaterials that are inherently bandwidth limited. We perform microwave experiments to confirm our findings.
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.
Fernandez-Dominguez AI, Luo Y, Zhao R, et al., 2018, Plasmonics and Transformation Optics, WORLD SCIENTIFIC HANDBOOK OF METAMATERIALS AND PLASMONICS, VOL 4: RECENT PROGRESS IN THE FIELD OF NANOPLASMONICS, Editors: Maier, Aizpurua, Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 147-196, ISBN: 978-981-3227-65-1
Pendry JB, Huidobro PA, Luo Y, et 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.
Demetriadou A, Hamm J, Luo Y, et al., 2017, Spatio-temporal dynamics and control of strong coupling in plasmonic nano-cavities, ACS Photonics, Vol: 4, Pages: 2410-2418, ISSN: 2330-4022
In the light-matter strong coupling regime, the excited state of quantum emitters is inextricably linked to a photonic mode, leading to hybrid states that are part-light and part-matter. Recently, there has been huge effort to realize strong coupling with nanoplasmonics, since it provides a versatile environment to study and control molecules in ambient conditions. Amongst the most promising designs are plasmonic nano-cavities that confine light to unprecedentedly small volumes. Such nano-cavities though support multiple types of modes, with different field profiles and radiative decay rates (bright and dark modes). Here, we show theoretically that the different nature of these modes leads to mode beating within the nano-cavity and the Rabi-oscillations, which alters the spatio-temporal dynamics of the hybrid system. By specifically designing the illumination set-up, we decompose and control the dark and bright plasmon mode excitation and therefore their coupling with quantum emitters. Hence, this work opens new routes for dynamically dressing emitters, to tailor their hybrid states with external radiation.
Zhang Y-L, Pendry JB, Lei DY, 2017, Radial anisotropy from a geometric viewpoint: Topological singularity and effective medium realization, PHYSICAL REVIEW B, Vol: 96, ISSN: 2469-9950
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