62 results found
Sapienza R, Pendry J, Maier S, et 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.
De Paz MB, González-Tudela A, Huidobro PA, 2022, Manipulating generalized Dirac cones in subwavelength dipolar arrays, Physical Review A, Vol: 106, ISSN: 2469-9926
We discuss the emergence and manipulation of generalized Dirac cones in the subradiant collective modes of a subwavelength dipolar array. We consider a collection of single quantum emitters modeled as point dipoles arranged in a honeycomb lattice with subwavelength periodicity. While conventional honeycomb arrays host bound modes that display Dirac cones at the K and K′ points, we show that introducing uniaxial anisotropy in the lattice results in modified dispersion relations. These include the tilting of Dirac cones arising purely due to long-range, retarded, electromagnetic coupling in the lattice, which changes the local density of states at the Dirac point from vanishing (type I) to diverging (types II and III), the emergence of semi-Dirac points, with linear and quadratic dispersions in orthogonal directions, and the anisotropic movement of Dirac cones away from the K and K′ points. Such energy dispersions can modify substantially the dynamics of local probes, such as quantum emitters, for which they have been shown to induce anisotropic power-law interactions.
Blanco de Paz M, Herrera MAJ, Arroyo Huidobro P, et al., 2022, Energy density as a probe of band representations in photonic crystals, JOURNAL OF PHYSICS-CONDENSED MATTER, Vol: 34, ISSN: 0953-8984
- Author Web Link
- Citations: 2
Galiffi E, Huidobro PA, Pendry JB, 2022, Publisher Correction: An Archimedes’ screw for light, Nature Communications, Vol: 13, Pages: 1-1, ISSN: 2041-1723
Pendry JB, Galiffi E, Huidobro PA, 2022, Photon conservation in trans-luminal metamaterials, Optica, Vol: 9, Pages: 724-730, ISSN: 2334-2536
Structures that appear to move at or near the velocity of light contain singular points. Energy generated by motion accumulates at these points into ever-narrowing peaks. In this paper, we show that energy is generated by a curious process that conserves the number of photons, adding energy by forcing photons already present to climb a ladder of increasing frequency. We present both a classical proof based on conservation of lines of force, and a more formal quantum electrodynamics proof demonstrating the absence of unpaired creation and annihilation operators. Exceptions to this rule are found when negative frequencies make an appearance. Finally, we make a connection to laboratory-based models of black holes and Hawking radiation.
Rider MS, Buendia A, Abujetas DR, et al., 2022, Advances and Prospects in Topological Nanoparticle Photonics, ACS PHOTONICS, Vol: 9, Pages: 1483-1499, ISSN: 2330-4022
- Author Web Link
- Citations: 5
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.
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.
Piccardo M, Ginis V, Forbes A, et al., 2022, Roadmap on multimode light shaping, JOURNAL OF OPTICS, Vol: 24, ISSN: 2040-8978
- Author Web Link
- Citations: 19
Galiffi E, Tirole R, Yin S, et al., 2022, Photonics of time-varying media, ADVANCED PHOTONICS, Vol: 4
- Author Web Link
- Citations: 42
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.
Redondo-Yuste J, Blanco de Paz M, Huidobro PA, et al., 2021, Quantum electrodynamics in anisotropic and tilted Dirac photonic lattices, NEW JOURNAL OF PHYSICS, Vol: 23, ISSN: 1367-2630
- Author Web Link
- Citations: 1
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
Huidobro PA, Silveirinha MG, Galiffi E, et al., 2021, Homogenization theory of space-time metamaterials, Physical Review Applied, Vol: 16, Pages: 1-13, ISSN: 2331-7019
We present a general framework for the homogenization theory of space-time metamaterials. By mapping to a frame comoving with the space-time modulation, we derive analytical formulas for the effective material parameters for traveling-wave modulations in the low-frequency limit: electric permittivity, magnetic permeability, and magnetoelectric coupling. In doing so, we provide a recipe for the calculation of effective parameters of space–time-modulated media where the parameters follow a traveling-wave form of any shape and we show how synthetic motion can result in giant bianisotropy. This allows us to deepen the understanding of how nonreciprocity can be achieved in the long-wavelength limit and to completely characterize the different nonreciprocal behaviors available in space–time-modulated media. In particular, we show how the modulation speed, which can be subluminal or superluminal, together with the relative phase between electric and magnetic modulations, provide tuning knobs for the nonreciprocal response of these systems. Furthermore, we apply the theory to derive exact formulas for the Fresnel drag experienced by light traveling through traveling-wave modulations of electromagnetic media, providing insight into the differences and similarities between synthetic motion and moving matter. Since we exploit a series of Galilean coordinate transformations, the theory may be generalized to other kinds of waves.
Galiffi E, Silveirinha MG, Huidobro PA, et al., 2021, Photon localization and Bloch symmetry breaking in luminal gratings, Physical Review B: Condensed Matter and Materials Physics, Vol: 104, Pages: 1-6, ISSN: 1098-0121
In gratings synthetically moving at nearly the velocity of light a symmetry breaking transition is observed between free-flowing fluidlike Bloch waves observed at lower grating velocities and, at luminal velocities, condensed, localized states of light captured in each period of the grating and locked to its velocity. We introduce a technique for calculating in this regime and use it to study the transition in detail shedding light on the critical exponents and the periodic oscillations in transmitted intensity seen in the pretransition regime.
Pendry JB, Galiffi E, Huidobro PA, 2021, Gain mechanism in time-dependent media, OPTICA, Vol: 8, Pages: 636-637, ISSN: 2334-2536
- Author Web Link
- Citations: 13
Proctor M, Blanco de Paz M, Bercioux D, et al., 2021, Higher-order topology in plasmonic Kagome lattices, APPLIED PHYSICS LETTERS, Vol: 118, ISSN: 0003-6951
- Author Web Link
- Citations: 10
Proctor M, Huidobro PA, Bradlyn B, et al., 2020, Robustness of topological corner modes in photonic crystals, PHYSICAL REVIEW RESEARCH, Vol: 2
- Author Web Link
- Citations: 25
Proctor M, Xiao X, Craster RV, et al., 2020, Near- and far-field excitation of topological plasmonic metasurfaces, Photonics, Vol: 7, ISSN: 2304-6732
The breathing honeycomb lattice hosts a topologically non-trivial bulk phase due to the crystalline-symmetry of the system. Pseudospin-dependent edge states, which emerge at the interface between trivial and non-trivial regions, can be used for the directional propagation of energy. Using the plasmonic metasurface as an example system, we probe these states in the near- and far-field using a semi-analytical model. We provide the conditions under which directionality was observed and show that it is source position dependent. By probing with circularly-polarised magnetic dipoles out of the plane, we first characterise modes along the interface in terms of the enhancement of source emissions due to the metasurface. We then excite from the far-field with non-zero orbital angular momentum beams. The position-dependent directionality holds true for all classical wave systems with a breathing honeycomb lattice. Our results show that a metasurfac,e in combination with a chiral two-dimensional material, could be used to guide light effectively on the nanoscale.
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
- Author Web Link
- Citations: 26
Yang F, Huidobro PA, Pendry JB, 2020, Electron Energy Loss Spectroscopy of Singular Plasmonic Metasurfaces, LASER & PHOTONICS REVIEWS, Vol: 14, ISSN: 1863-8880
- Author Web Link
- Citations: 2
Proctor M, Huidobro PA, Maier SA, et al., 2020, Manipulating topological valley modes in plasmonic metasurfaces, Nanophotonics, Vol: 9, Pages: 657-665, ISSN: 2192-8606
The coupled light-matter modes supported by plasmonic metasurfaces can be combined with topological principles to yield subwavelength topological valley states of light. We give a systematic presentation of the topological valley states available for lattices of metallic nanoparticles: All possible lattices with hexagonal symmetry are considered, as well as valley states emerging on a square lattice. Several unique effects which have yet to be explored in plasmonics are identified, such as robust guiding, filtering and splitting of modes, as well as dual-band effects. We demonstrate these by means of scattering computations based on the coupled dipole method that encompass the full electromagnetic interactions between nanoparticles.
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.
Huidobro PA, Fernandez-Dominguez A, 2020, Transformation optics for plasmonics: from metasurfaces to excitonic strong coupling, COMPTES RENDUS PHYSIQUE, Vol: 21, Pages: 389-408, ISSN: 1631-0705
- Author Web Link
- Citations: 4
Proctor M, Craster RV, Maier SA, et al., 2019, Exciting pseudospin-dependent edge states in plasmonic metasurfaces, ACS Photonics, Vol: 6, Pages: 2985-2995, ISSN: 2330-4022
We study a plasmonic metasurface that supports pseudospin-dependent edge states confined at a subwavelength scale, considering full electrodynamic interactions including retardation and radiative effects. The spatial symmetry of the lattice of plasmonic nanoparticles gives rise to edge states with properties reminiscent of the quantum spin Hall effect in topological insulators. However, unlike the spin-momentum locking characteristic of topological insulators, these modes are not purely unidirectional and their propagation properties can be understood by analyzing the spin angular momentum of the electromagnetic field, which is inhomogeneous in the plane of the lattice. The local sign of the spin angular momentum determines the propagation direction of the mode under a near-field excitation source. We also study the optical response under far-field excitation and discuss in detail the effects of radiation and retardation.
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.
Pocock S, Huidobro PA, Giannini V, 2019, Bulk-edge correspondence and long range hopping in the topological plasmonic chain, Nanophotonics, Vol: 8, Pages: 1337-1347, ISSN: 2192-8606
The existence of topologically protected edge modes is often cited as a highly desirable trait of topological insulators. However, these edge states are not always present. A realistic physical treatment of long-range hopping in a one-dimensional dipolar system can break the symmetry that protects the edge modes without affecting the bulk topological number, leading to a breakdown in bulk-edge correspondence (BEC). Hence, it is important to gain a better understanding of where and how this occurs, as well as how to measure it. Here we examine the behaviour of the bulk and edge modes in a dimerised chain of metallic nanoparticles and in a simpler non-Hermitian next-nearest-neighbour model to provide some insights into the phenomena of bulk-edge breakdown. We construct BEC phase diagrams for the simpler case and use these ideas to devise a measure of symmetry-breaking for the plasmonic system based on its bulk properties. This provides a parameter regime in which BEC is preserved in the topological plasmonic chain, as well as a framework for assessing this phenomenon in other systems.
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.
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