arXiv subjects

Mario G. Silveirinha

Publications and source records attributed to Mario G. Silveirinha.

At least 37 records · Page 2Linked to original sources

arXiv2019

Robust surface plasmon polaritons on gyrotropic interfaces

Unidirectional surface plasmon polaritons (SPPs) at the interface between a gyrotropic medium and a simple medium are studied in a newly-recognized frequency regime wherein the SPPs form narrow, beam-like patterns due to hyperbolic dispersion. The SPP beams are steerable by controlling parameters such as the cyclotron frequency (external bias) or the frequency of operation. The bulk band structure along different propagation directions is examined to ascertain a common bandgap, valid for all propagation directions, which the SPPs cross. The case of a finite-thickness gyrotropic slab is also considered, for which we present the Green function and examine the thickness and loss level required to maintain a unidirectional SPP.

physics.optics↗

arXiv2019

Lateral Optical Forces on Linearly-Polarized Emitters near a Reciprocal Substrate

We theoretically investigate the emergence of lateral (recoil) forces acting on generic dipole-type emitters in the vicinity of a reciprocal translation-invariant substrate. Surprisingly, we find that for linearly-polarized electric dipoles the lateral force invariably vanishes, independent of the anisotropy (e.g., tilted optical axes) or chirality of the substrate. We identify a novel opportunity to have a recoil force relying on a superposition of two linearly-polarized and collinear electric and magnetic dipoles. Counterintuitively, it is shown that when such an emitter stands above a uniaxial dielectric half-space with tilted optical axes it may experience a recoil force oriented along the direction perpendicular to the plane defined by the interface normal and the substrate optical axis.

physics.optics↗

arXiv2019

Proof of the bulk-edge correspondence through a link between topological photonics and fluctuation-electrodynamics

The bulk-edge correspondence links the Chern-topological numbers with the net number of unidirectional states supported at an interface of the relevant materials. This fundamental principle is perhaps the most consequential result of topological photonics, as it determines the precise physical manifestations of nontrivial topological features. Even though the bulk-edge correspondence has been extensively discussed and used in the literature, it seems that in the general photonic case with dispersive materials it has no solid mathematical foundation and is essentially a conjecture. Here, I present a rigorous demonstration of this fundamental principle by showing that the thermal fluctuation-induced light-angular momentum spectral density in a closed cavity can be expressed in terms of the photonic gap Chern number, as well as in terms of the net number of unidirectional edge states. In particular, I highlight the rather fundamental connections between topological numbers in Chern-type photonic insulators and the fluctuation-induced light-momentum

physics.optics↗

arXiv2019

Modal expansions in dispersive material systems with application to quantum optics and topological photonics

It is proven that in the lossless case the electrodynamics of a generic inhomogeneous possibly bianisotropic and nonreciprocal system may be described by an augmented state-vector whose time evolution is determined by a Hermitian operator. As a consequence, it is shown that a generic electromagnetic field distribution can be expanded into a complete set of normal modes that satisfy generalized orthogonality relations. Importantly, the modal expansions in dispersive systems are not unique because the electromagnetic degrees of freedom span only part of the entire Hilbert space. The developed theory is used to obtain a modal expansion of the system Green's function. Furthermore, it is highlighted that the Hermitian-type formulation of the dispersive Maxwell's equations enables one to extend the powerful ideas of topological photonics to a wide range of electromagnetic systems and to characterize electromagnetic topological phases. In addition, we illustrate how the developed formalism can be applied to quantum optics. We present a simple procedure to quantize the electromagnetic field in a generic bianisotropic and nonreciprocal cavity and derive the quantum correlations of the electromagnetic fields.

physics.optics↗

arXiv2018

Exact Solution for the Protected TEM edge mode in a PTD-Symmetric Parallel-Plate Waveguide

A Parity Time-reversal Dual (PTD) symmetric structure constituted by a Perfectly-Electric-Perfectly magnetic (PEC-PMC) parallel plate waveguide (PPW) is analyzed. This waveguide supports unimodal transverse electromagnetic (TEM) edge mode propagation protected against back-scattering from a certain class of deformations and defects. The TEM solution is found in analytical form by using three different methods, namely conformal mapping, mode-matching, and Fourier-transform methods. It is shown through numerical simulations that the mode propagation is robust with respect to deformations such as 90° bends and discontinuity such as transition to free-space. Implementation of the PMC boundary conditions via both a bed of nails and a mushroom structure is also successfully investigated.

physics.class-ph↗

arXiv2018

Topologically induced transparency in a two-phase metamaterial

It is theoretically and numerically demonstrated that a mixture of two topologically distinct material phases is characterized by an anomalous "transparency window" in a spectral range wherein the individual material phases are strongly reflecting. In particular, it is shown that a metamaterial formed by a metallic wire grid embedded in a magnetized plasma may support the propagation of waves with long wavelengths, notwithstanding the components, when taken separately, completely block the electromagnetic radiation. The effect is explained in terms of the topological properties of the magnetoplasmon. Furthermore, it is highlighted that some naturally available materials may be regarded as a mixture of two topologically distinct phases, and hence may be as well characterized by a similar anomalous transparency effect.

physics.optics↗

arXiv2017

Revisiting the Abraham-Minkowski Dilemma

Here, the Abraham-Minkowski controversy on the correct definition of the light momentum in a macroscopic medium is revisited with the purpose to highlight that an effective medium formalism necessarily restricts the available information on the internal state of a system, and that this is ultimately the reason why the dilemma has no universal solution. Despite these difficulties, it is demonstrated that in the limit of no material absorption and under steady-state conditions, the time-averaged light (kinetic) momentum may be unambiguously determined by the Abraham result, both for bodies at rest and for circulatory flows of matter. The implications of these findings are discussed in the context of quantum optics of moving media, and we examine in detail the fundamental role of the Minkowski momentum in such a context.

physics.optics↗

arXiv2017

Topological Angular Momentum and Radiative Heat Transport in Closed Orbits

Here, we study the role of topological edge states of light in the transport of thermally generated radiation in a closed cavity at a thermodynamic equilibrium. It is shown that even in the zero temperature limit - when the field fluctuations are purely quantum mechanical - there is a persistent flow of electromagnetic momentum in the cavity in closed orbits, deeply rooted in the emergence of spatially separated unidirectional edge state channels. It is highlighted the electromagnetic orbital angular momentum of the system is nontrivial, and that the energy circulation is towards the same direction as that determined by incomplete cyclotron orbits near the cavity walls. Our findings open new inroads in topological photonics and suggest that topological states of light can determine novel paradigms in the context of radiative heat transport.

physics.optics↗

arXiv2016

PTD Symmetry Protected Scattering Anomaly in Optics

In time-reversal invariant electronic systems the scattering matrix is anti-symmetric. This property enables an effect, designated here as "scattering anomaly", such that the electron transport does not suffer from back reflections, independent of the specific geometry of the propagation path or the presence of time-reversal invariant defects. In contrast, for a generic time-reversal invariant photonic system the scattering matrix is symmetric and there is no similar anomaly. Here, it is theoretically proven that despite these fundamental differences there is a wide class of photonic platforms - in some cases formed only by time-reversal invariant media - in which a scattering anomaly can occur. It is shown that an optical system invariant under the action of the composition of the parity, time-reversal, and duality operators (PTD) is characterized by an anti-symmetric scattering matrix. Specific examples of photonic platforms wherein the scattering anomaly occurs are given, and it is demonstrated with full wave numerical simulations that the proposed systems enable bidirectional waveguiding immune to arbitrary deformations of the propagation path. Importantly, our theory unveils a new class of fully three dimensional structures wherein the transport of light is fully protected against reflections and uncovers unsuspected links between the electrodynamics of reciprocal and nonreciprocal materials.

physics.optics↗

arXiv2016

Bulk-edge correspondence for topological photonic continua

Here, building on our previous work [Phys. Rev. B, 92, 125153, (2015)], it is shown that the propagation of unidirectional gapless edge states at an interface of two topologically distinct electromagnetic continua with a well-behaved asymptotic electromagnetic response is rigorously predicted by the bulk-edge correspondence principle. We work out detailed examples demonstrating that when the spatial-cut off of the nonreciprocal part of the material response is considered self-consistently in the solution of the relevant electromagnetic problem, the number of unidirectional gapless edge modes is identical to the difference of the Chern numbers of the bulk materials. Furthermore, it is shown how the role of the spatial cut-off can be imitated in realistic systems using a tiny air gap with a specific thickness. This theory provides a practical roadmap for the application of topological concepts to photonic platforms formed by nonreciprocal electromagnetic continua.

physics.optics↗

arXiv2016

Effective Medium Theory of Electromagnetic and Quantum Metamaterials

Here, we present an overview of recent developments in the characterization of electromagnetic and quantum metamaterials using effective medium methods. It is highlighted that both electromagnetic and electronic systems can be homogenized in a unified manner based on the introduction of an effective Hamiltonian operator that describes the time evolution of the macroscopic initial states as well as the stationary states of the relevant system. Furthermore, it is shown that in some circumstances quadratic forms of the fields, such as the energy, can be exactly determined using the effective medium theory.

cond-mat.mes-hall↗

arXiv2016

$\mathbb{Z}_{2}$ Topological Index for Continuous Photonic Materials

Electronic topological insulators are one of the breakthroughs of the 21st century condensed matter physics. So far, the search for a light counterpart of an electronic topological insulator has remained elusive. This is due to the fundamentally different natures of light and matter and the different spins of photons and electrons. Here, it is shown that the theory of electronic topological insulators has a genuine analogue in the context of light wave propagation in time-reversal invariant continuous materials. We introduce a Gauge invariant $Z_2$ index that depends on the global properties of the photonic band structure and is robust to any continuous weak variation of the material parameters that preserves the time-reversal invariance. A nontrivial $Z_2$ index has two possible causes: (i) the lack of smoothness of the pseudo-Hamiltonian in the ${\bf{k}} \to \infty$ limit, and (ii) the entanglement between positive and negative frequency eigenmode branches. In particular, it is proven that electric-type plasmas and magnetic-type plasmas are topologically inequivalent for a fixed wave polarization. We propose a bulk-edge correspondence that links the number of edge modes with the topological invariants of two continuous bulk materials, and present detailed numerical examples that illustrate the application of the theory.

cond-mat.mes-hall↗

arXiv2014

Optical instabilities and spontaneous light emission by polarizable moving matter

One of the most extraordinary manifestations of the coupling of the optical field and matter is the emission of light by charged particles passing through a dielectric medium: the Vavilov-Cherenkov effect. In this article, it is theoretically predicted that a related phenomenon may be observed when neutral fast polarizable particles travel near a metal surface supporting surface plasmon polaritons. Rather dramatically, it is found that at some critical velocity, even if the initial optical field is vanishingly small, the system may become unstable and may start spontaneously emitting light such that in some initial time window the optical field grows exponentially with time.

physics.optics↗

arXiv2014

Theory of Quantum Friction

Here, we develop a comprehensive quantum theory for the phenomenon of quantum friction. Based on a theory of macroscopic quantum electrodynamics for unstable systems, we calculate the quantum expectation of the friction force, and link the friction effect to the emergence of system instabilities related to the Cherenkov effect. These instabilities may occur due to the hybridization of particular guided modes supported by the individual moving bodies, and selection rules for the interacting modes are derived. It is proven that the quantum friction effect can take place even when the interacting bodies are lossless and made of nondispersive dielectrics.

quant-ph↗

arXiv2013

Quantization of the Electromagnetic Field in Non-dispersive Polarizable Moving Media above the Cherenkov Threshold

We quantize the macroscopic electromagnetic field in a system of non-dispersive polarizable bodies moving at constant velocities possibly exceeding the Cherenkov threshold. It is shown that in general the quantized system is unstable and neither has a ground state nor supports stationary states. The quantized Hamiltonian is written in terms of quantum harmonic oscillators associated with both positive and negative frequencies, such that the oscillators associated with symmetric frequencies are coupled by an interaction term that does not preserve the quantum occupation numbers. Moreover, in the linear regime the amplitudes of the fields may grow without limit provided the velocity of the moving bodies is enforced to be constant. This requires the application of an external mechanical force that effectively pumps the system.

quant-ph↗

arXiv2013

Theory of Spatial Optical Solitons in Metallic Nanowire Materials

We characterize the spatial optical solitons supported by arrays of metallic nanowires embedded in Kerr-type material. The array of nanowires is described using an effective medium model and is regarded as a continuous medium. It is shown that the conditions necessary for the formation of spatial-solitons are radically different in presence of the nanowires, and in particular within the effective medium model spatial-solitons are allowed in the nanowire material only in case the host material is a "self-defocusing" material. It is proven that the characteristic soliton beamwidth is related to the degree of hyperbolicity of the isofrequency surfaces of the photonic states, and that a sufficiently strong electric field amplitude may enable subwavelength solitary waves.

cond-mat.mes-hall↗

arXiv2012

Transformation Electronics: Tailoring Electron's Effective Mass

The speed of integrated circuits is ultimately limited by the mobility of electrons or holes, which depend on the effective mass in a semiconductor. Here, building on an analogy with electromagnetic metamaterials and transformation optics, we describe a new transport regime in a semiconductor superlattice characterized by extreme anisotropy of the effective mass and a low intrinsic resistance to movement - with zero effective mass - along some preferred direction of electron motion. We theoretically demonstrate that such regime may permit an ultra fast, extremely strong electron response, and significantly high conductivity, which, notably may be weakly dependent on the temperature at low temperatures. These ideas may pave the way for faster electronic devices and detectors and new functional materials with a strong electrical response in the infrared regime.

cond-mat.mes-hall↗

arXiv2012

A Metamaterial-Inspired Model for Electron Waves in Bulk Semiconductors

Based on an analogy with electromagnetic metamaterials, we develop an effective medium description for the propagation of electron matter waves in bulk semiconductors with a zincblende structure. It is formally demonstrated that even though departing from a different starting point, our theory gives results for the energy stationary states consistent with Bastard's envelope function approximation in the long-wavelength limit. Using the proposed approach, we discuss the time evolution of a wave packet in a bulk semiconductor with a zero-gap and linear energy-momentum dispersion.

cond-mat.mes-hall↗