Publications
470 results found
Pendry JB, Horsley SAR, 2024, QED in space–time varying materials, APL Quantum, Vol: 1
<jats:p>Space–time variation spoils frequency conservation and brings negative frequencies into the picture. In addition, the quantum nature of light comes to the fore in a manner not evident in static systems. Here, we explore the quantum structure of these systems; propose a Hamiltonian; show that, in the Heisenberg picture, quantum field operators evolve according to classical equations; and discuss the uniquely quantum phenomenon of photon-pair creation.</jats:p>
Serra JC, Galiffi E, Huidobro PA, et al., 2024, Particle-hole instabilities in photonic time-varying systems, Optical Materials Express, Vol: 14, Pages: 1459-1459
<jats:p>Photonic systems with time-varying modulations have attracted considerable attention as they allow for the design of non-reciprocal devices without the need for an external magnetic bias. Unlike time-invariant systems, such modulations couple modes with different frequencies. Here, we discuss how this coupling and particle-hole symmetry may lead to the resonant interaction of positive and negative frequency oscillators. To illustrate this idea, we analyze a dispersive spacetime crystal described by a Drude-Lorentz model with a traveling-wave modulation. Our findings demonstrate that the interaction between positive and negative frequency bands can induce parametric instabilities under certain conditions, stemming from the interplay between dispersion and spacetime modulations. In particular, we find that material dispersion creates the conditions for the formation of instabilities for arbitrarily small modulations speeds in the absence of dissipation mechanisms.</jats:p>
Pendry JB, 2024, Air conditioning for photons [Invited], Optical Materials Express, Vol: 14, Pages: 407-407
<jats:p>A simple time dependent system is solved analytically taking the form of a moving step-up or step-down in refractive index. We demonstrate that step motion, by a process of compression or expansion, adds or subtracts energy from radiation passing through, so heating or cooling the photons.</jats:p>
Horsley SAR, Pendry JB, 2023, Quantum electrodynamics of time-varying gratings., Proc Natl Acad Sci U S A, Vol: 120
Gratings which are in apparent motion reveal some startling properties for classical radiation, especially for luminal gratings traveling at or around the speed of light. We show here that their quantum properties are even more remarkable, their effective refractive index modeling the Schwarzschild singularity which as we show generates spontaneous Hawking radiation in correlated photon pairs. Subjected to external radiation, luminal gratings provoke stimulated emission of photon pairs which we propose as a possible means of observing Hawking radiation in the laboratory.
Guan F, Guo X, Zeng K, et al., 2023, Overcoming losses in superlenses with synthetic waves of complex frequency., Science, Vol: 381, Pages: 766-771
Superlenses made of plasmonic materials and metamaterials can image features at the subdiffraction scale. However, intrinsic losses impose a serious restriction on imaging resolution, a problem that has hindered widespread applications of superlenses. Optical waves of complex frequency that exhibit a temporally attenuating behavior have been proposed to offset the intrinsic losses in superlenses through the introduction of virtual gain, but experimental realization has been lacking because of the difficulty of imaging measurements with temporal decay. In this work, we present a multifrequency approach to constructing synthetic excitation waves of complex frequency based on measurements at real frequencies. This approach allows us to implement virtual gain experimentally and observe deep-subwavelength images. Our work offers a practical solution to overcome the intrinsic losses of plasmonic systems for imaging and sensing applications.
Valev VK, Engheta N, Pendry JB, 2023, Photonic Nanomaterials are Lighting the Way, ADVANCED MATERIALS, Vol: 35, ISSN: 0935-9648
Tirole R, Vezzoli S, Galiffi E, et al., 2023, Double-slit time diffraction at optical frequencies, Nature Physics, Vol: 19, Pages: 999-1002, ISSN: 1745-2473
Double-slit experiments—where a wave is transmitted through a thin double aperture in space—have confirmed the wave–particle duality of quantum objects, such as single photons, electrons, neutrons, atoms and large molecules. Yet, the temporal counterpart of Young’s double-slit experiment—a wave interacting with a double temporal modulation of an interface—remains elusive. Here we report such a time-domain version of the classic Young’s double-slit experiment: a beam of light twice gated in time produces an interference in the frequency spectrum. The ‘time slits’, narrow enough to produce diffraction at optical frequencies, are generated from the optical excitation of a thin film of indium tin oxide near its epsilon-near-zero point. The separation between time slits determines the period of oscillations in the frequency spectrum, whereas the decay of fringe visibility in frequency reveals the shape of the time slits. Surprisingly, many more oscillations are visible than expected from existing theory, implying a rise time that approaches an optical cycle. This result enables the further exploration of time-varying physics, towards the spectral synthesis of waves and applications such as signal processing and neuromorphic computation.
Oue D, Ding K, Pendry JB, 2023, Noncontact frictional force between surfaces by peristaltic permittivity modulation, PHYSICAL REVIEW A, Vol: 107, ISSN: 2469-9926
Pendry JB, 2023, Photon number conservation in time dependent systems [Invited], OPTICS EXPRESS, Vol: 31, Pages: 452-458, ISSN: 1094-4087
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- Citations: 2
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.
Liu Y, Wang GP, Pendry JB, et al., 2022, All-angle reflectionless negative refraction with ideal photonic Weyl metamaterials, LIGHT-SCIENCE & APPLICATIONS, Vol: 11, ISSN: 2095-5545
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- Citations: 8
Zagar C, Krammer FGP, Pendry JB, et al., 2022, Optical response of hyperbolic metamaterials with adsorbed nanoparticle arrays, Nanoscale Horizons, Vol: 7, Pages: 1228-1239, ISSN: 2055-6756
Experimental studies of have been recently performed to determine the optical effect of adsorption of arrays of gold nanoparticles, NPs (16 nm or 40 nm in diameter) on reflective substrates (Ma et al., ACS Photonics, 2018, 5, 4604–4616; Ma et al., ACS Nano, 2020, 14, 328–336) and on transparent interfaces (Montelongo et al., Nat. Mater., 2017, 16, 1127–1135). As predicted by the theory (Sikdar et al., Phys. Chem. Chem. Phys., 2016, 18, 20486–20498), a reflection quenching effect was observed on the reflective substrates, in the frequency domain centred around the nanoparticle localised plasmon resonance. Those results showed a broad dip in reflectivity, which was deepening and red-shifting with increasing array densities. In contrast, the second system has shown, also in accordance with the theory (Sikdar and Kornyshev, Sci. Rep., 2016, 6, 1–16), a broad reflectivity peak in the same frequency domain, increasing in intensity and shifting to the red with densification of the array. In the present paper, we develop a theory of an optical response of NP arrays adsorbed on the surface of stacked nanosheet hyperbolic substrates. The response varies between quenched and enhanced reflectivity, depending on the volume fractions of the metallic and dielectric components in the hyperbolic metamaterial. We reproduce the results of the earlier works in the two opposite limiting cases – of a pure metal and a pure dielectric substrates, while predicting novel resonances for intermediate compositions. Whereas the metal/dielectric ratio in the hyperbolic substrate cannot be changed in time – for each experiment a new substrate should be fabricated – the density of the adsorbed nanoparticle arrays can be controlled in real time in electrochemical photonic cells (Montelongo et al., Nat. Mater., 2017, 16, 1127–1135; Ma et al., ACS Photonics, 2018, 5, 4604–4616; Ma et al., ACS Nano, 2020, 14, 328–336). Therefore, we syst
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.
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.
Oue D, Ding K, Pendry J, 2022, Cerenkov radiation in vacuum from a superluminal grating, Physical Review Research, Vol: 4, Pages: 1-6, ISSN: 2643-1564
Nothing can physically travel faster than light in vacuum. There are several ways proposed to bypass the light barrier and produce ˇCerenkov radiation ( ˇCR) in vacuum. In this article, we theoretically predict ˇCR in vacuum from a spatiotemporally modulated boundary. We consider the modulation of traveling wave type and apply a uniform electrostatic field on the boundary to generate electric dipoles. Since the induced dipoles stick to the interface, they travel at the modulation speed. When the grating travels faster than light, it emits ˇCR. In order to quantitatively examine this argument, we need to calculate the field scattered at the boundary. We utilise a dynamicaldifferential method, which we developed in the previous paper, to quantitatively evaluate the field distribution in such a situation. We can confirm that all scattered fields are evanescent if the modulation speed is slower than light while some become propagating if the modulation is fasterthan light.
Galiffi E, Yin S, Huidobro PA, et al., 2022, Wave Scattering in Dynamical Media
In this talk we report on recent theoretical explorations in the context of time-varying media, aiming at offering a few perspectives on the peculiarities of wave scattering from abrupt, continuous, periodic, chiral and dispersive temporal inhomogeneities, as well as their implications for distinct forms of wave amplification, localization nonreciprocity, frequency modulation and harmonic generation.
Galiffi E, Tirole R, Yin S, et al., 2022, Photonics of time-varying media, ADVANCED PHOTONICS, Vol: 4
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- Citations: 101
Piccardo M, Ginis V, Forbes A, et al., 2022, Roadmap on multimode light shaping, JOURNAL OF OPTICS, Vol: 24, ISSN: 2040-8978
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- Citations: 26
Pendry J, Huidobro P, Silveirinha M, et al., 2021, Crossing the light line, Nanophotonics, Vol: 11, Pages: 161-167, ISSN: 2192-8606
We ask the question “what happens to Bloch waves in gratings synthetically moving at near the speed of light?”. First we define a constant refractive index (CRI) model in which Bloch waves remain well defined as they break the light barrier, then show their dispersion rotating through 360° from negative to positive and back again. Next we introduce the effective medium approximation (EMA) then refine it into a 4-wave model which proves to be highly accurate. Finally using the Bloch waves to expand a pulse of light we demonstrate sudden inflation of pulse amplitude combined with reversal of propagation direction as a luminal grating is turned on.
Lu L, Ding K, Galiffi E, et al., 2021, Revealing topology with transformation optics, Nature Communications, Vol: 12, Pages: 1-7, ISSN: 2041-1723
Symmetry deepens our insight into a physical system and its interplay with topology enables the discovery of topological phases. Symmetry analysis is conventionally performed either in the physical space of interest, or in the corresponding reciprocal space. Here we borrow the concept of virtual space from transformation optics to demonstrate how a certain class of symmetries can be visualised in a transformed, spectrally related coordinate space, illuminating the underlying topological transitions. By projecting a plasmonic system in a higher-dimensional virtual space onto a lower-dimensional system in real space, we show how transformation optics allows us to construct a topologically non-trivial system by inspecting its modes in the virtual space. Interestingly, we find that the topological invariant can be controlled via the singularities in the conformal mapping, enabling the intuitive engineering of edge states. The confluence of transformation optics and topology here can be generalized to other wave realms beyond photonics.
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.
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.
Oue D, Ding K, Pendry JB, 2021, Calculating spatiotemporally modulated surfaces: A dynamical differential formalism, PHYSICAL REVIEW A, Vol: 104, ISSN: 2469-9926
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- Citations: 4
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.
Zhu X, Wang H, Lei D, et al., 2021, Designing plasmonic exceptional points by transformation optics, OPTICS EXPRESS, Vol: 29, Pages: 16046-16055, ISSN: 1094-4087
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- Citations: 2
Pendry JB, Galiffi E, Huidobro PA, 2021, Gain mechanism in time-dependent media, OPTICA, Vol: 8, Pages: 636-637, ISSN: 2334-2536
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- Citations: 17
Tirole R, Attavar T, Dranczewski J, et al., 2021, Time Diffraction in an Epsilon-Near-Zero Metasurface
We observe strong, efficient all-optical modulations and frequency-shift due to time diffraction in a thin film of ITO over gold. Excitation of the Berreman mode leads to redshift and spectral broadening from a nonlinear grating.
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