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We analyze the coupling into a slotted cylindrical cavity operating at fundamental cavity modal frequencies overlapping with the slot’s first resonance frequency through an unmatched formulation th...

Mie-resonant dielectric metasurfaces are excellent candidates for both fundamental studies related to light-matter interactions and for numerous applications ranging from holography to sensing to nonlinear optics. To date, however, most applications using Mie metasurfaces utilize only weak light-matter interaction. Here, we go beyond the weak coupling regime and demonstrate for the first time strong polaritonic coupling between Mie photonic modes and intersubband (ISB) transitions in semiconductor heterostructures. Furthermore, along with demonstrating ISB polaritons with Rabi splitting as large as 10%, we also demonstrate the ability to tailor the strength of strong coupling by engineering either the semiconductor heterostructure or the photonic mode of the resonators. Unlike previous plasmonic-based works, our new all-dielectric metasurface approach to generate ISB polaritons is free from ohmic losses and has high optical damage thresholds, thereby making it ideal for creating novel and compact mid-infrared light sources based on nonlinear optics.

In this article, we examine the coupling into an electrically short azimuthal slot on a cylindrical cavity operating at fundamental cavity modal frequencies. We first develop a matched bound formulation through which we can gather information for maximum achievable levels of interior cavity fields. Actual field levels are below this matched bound; therefore, we also develop an unmatched formulation for frequencies below the slot resonance to achieve a better insight on the physics of this coupling. Good agreement is observed between the unmatched formulation, full-wave simulations, and experimental data, providing a validation of our analytical models. We then extend the unmatched formulation to treat an array of slots, found again in good agreement with full-wave simulations. These analytical models can be used to investigate ways to mitigate electromagnetic interference and electromagnetic compatibility effects within cavities.

Toroidal moment is an electromagnetic excitation that lies outside the familiar picture of electric and magnetic multipoles. It has recently been a topic of intense research in the fields of nanoph...

The Lorentz-like effective medium resonance (LEMR) exhibited by the longitudinal effective permittivity of semiconductor hyperbolic metamaterials (SHMs) has been known for some time. However, direct observation of this resonance proved to be difficult. Herein, we experimentally demonstrate its existence by strongly coupling SHMs to plasmonic metasurfaces. We consider four strong coupling implementations of SHMs that exhibit different LEMR absorption profiles (both in frequency and in strength) to validate our approach.

High-quality factor resonant cavities are challenging structures to model in electromagnetics owing to their large sensitivity to minute parameter changes. Therefore, uncertainty quantification (UQ) strategies are pivotal to understanding key parameters affecting the cavity response. We discuss here some of these strategies focusing on shielding effectiveness (SE) properties of a canonical slotted cylindrical cavity that will be used to develop credibility evidence in support of predictions made using computational simulations for this application.

This paper considers plane wave coupling to a transmission line consisting of an aerial wire above a conducting ground. Simple circuit models are constructed for the terminating impedances at the ends of the line including radiation effects. We consider the following load topologies: open circuit, short circuit, and grounded rods. Results from the transmission line model with these loads show good agreement with full-wave simulations.

In a transmission line, we evaluate the coupling between a line and a tower above ground when the excitation is an El high-altitude electromagnetic pulse (HEMP). Our model focuses on capturing correctly the effect of the coupling on the peak of the HEMP induced current that propagates along the line. This assessment is necessary to accurately estimate the effect of the excitation on the systems and components of the power grid. This analysis is a step towards a quantitative evaluation of HEMP excitation on the power grid.

We demonstrate an extremely nonlinear all-dielectric metasurface that employs intersubband polaritons to achieve a second-harmonic conversion coefficient of 3 mW/W2, and second-harmonic power conversion efficiency of 0.045% at a modest pump intensity of 6.7 kW/cm2.

In this paper we develop a fully-retarded, dipole approximation model to estimate the effective polarizabilities of a dimer made of dielectric resonators. They are computed from the polarizabilities of the two resonators composing the dimer. We analyze the situation of full-cubes as well as split-cubes, which have been shown to exhibit overlapping electric and magnetic resonances. We compare the effective dimer polarizabilities to ones retrieved via full-wave simulations as well as ones computed via a quasi-static, dipole approximation. We observe good agreement between the fully-retarded solution and the full-wave results, whereas the quasi-static approximation is less accurate for the problem at hand. The developed model can be used to predict the electric and magnetic resonances of a dimer under parallel or orthogonal (to the dimer axis) excitation. This is particularly helpful when interested in locating frequencies at which the dimer will emit directional radiation.

Optical nonlinearities are intimately related to the spatial symmetry of the nonlinear media. For example, the second order susceptibility vanishes for centrosymmetric materials under the dipole approximation. The latter concept has been naturally extended to the metamaterials’ realm, sometimes leading to the (erroneous) hypothesis that second harmonic (SH) generation is negligible in highly symmetric meta-atoms. In this work we aim to show that such symmetric meta-atoms can radiate SH light efficiently. In particular, we investigate in-plane centrosymmetric meta-atom designs where the approximation for meta-atoms breaks down. In a periodic array this building block allows us to control the directionality of the SH radiation. We conclude by showing that the use of symmetry considerations alone allows for the manipulation of the nonlinear multipolar response of a meta-atom, resulting in e.g. dipolar, quadrupolar, or multipolar emission on demand. This is because the size of the meta-atom is comparable with the free-space wavelength, thus invalidating the dipolar approximation for meta-atoms.

Dielectric metasurfaces that exploit the different Mie resonances of nanoscale dielectric resonators are a powerful platform for manipulating electromagnetic fields and can provide novel optical behavior. In this work, we experimentally demonstrate independent tuning of the magnetic dipole resonances relative to the electric dipole resonances of split dielectric resonators (SDRs). By increasing the split dimension, we observe a blue shift of the magnetic dipole resonance toward the electric dipole resonance. Therefore, SDRs provide the ability to directly control the interaction between the two dipole resonances within the same resonator. For example, we achieve the first Kerker condition by spectrally overlapping the electric and magnetic dipole resonances and observe significantly suppressed backward scattering. Moreover, we show that a single SDR can be used as an optical nanoantenna that provides strong unidirectional emission from an electric dipole source.

This paper details a model for the response of a finite- or an infinite-length wire interacting with a conducting ground to an electromagnetic pulse excitation. We develop a frequency–domain method based on transmission line theory that we name ATLOG – Analytic Transmission Line Over Ground. This method is developed as an alternative to full-wave methods, as it delivers a fast and reliable solution. It allows for the treatment of finite or infinite lossy, coated wires, and lossy grounds. The cases of wire above ground, as well as resting on the ground and buried beneath the ground are treated. The reported method is general and the time response of the induced current is obtained using an inverse Fourier transform of the current in the frequency domain. The focus is on the characteristics and propagation of the transmission line mode. Comparisons with full-wave simulations strengthen the validity of the proposed method.

Electromagnetic shields are usually employed to protect cables and other devices; however, these are generally not perfect, and may permit external magnetic and electric fields to penetrate into the interior regions of the cable, inducing unwanted current and voltages. The aim of this paper is to verify a circuit model tool with our previously proposed analytical model [1] for evaluating currents and voltages induced in the inner conductor of braided-shield cables. This circuit model will enable coupling between electromagnetic and circuit simulations.

We experimentally demonstrate strong coupling between Mie modes of dielectric resonators in a metasurface and intersubband transitions in semiconductor quantum wells that are embedded inside the resonator. The ability to achieve such light-matter coupling creates the possibility to realize ultrathin nonlinear optical devices that are free from complex phase matching requirements and have very high nonlinear conversion efficiencies.

We present a new approach to dielectric metasurface design that relies on a single resonator per unit cell and produces robust, high quality factor Fano resonances. Our approach utilizes symmetry breaking of highly symmetric resonator geometries, such as cubes, to induce couplings between the otherwise orthogonal resonator modes. In particular, we design perturbations that couple “bright” dipole modes to “dark” dipole modes whose radiative decay is suppressed by local field effects in the array. Our approach is widely scalable from the near-infrared to radio frequencies. We first unravel the Fano resonance behavior through numerical simulations of a germanium resonator-based metasurface that achieves a quality factor of ∼1300 at ∼10.8 μm. Then, we present two experimental demonstrations operating in the near-infrared (∼1 μm): a silicon-based implementation that achieves a quality factor of ∼350; and a gallium arsenide-based structure that achieves a quality factor of ∼600, the highest near-infrared qualit...

We study semiconductor hyperbolic metamaterials (SHMs) at the quantum limit experimentally using spectroscopic ellipsometry as well as theoretically using a new microscopic theory. The theory is a combination of microscopic density matrix approach for the material response and Green’s function approach for the propagating electric field. Our approach predicts absorptivity of the full multilayer system and for the first time allows the prediction of in-plane and out-of-plane dielectric functions for every individual layer constructing the SHM as well as effective dielectric functions that can be used to describe a homogenized SHM.

Metamaterials provide a means to tailor the spectral response of a surface. Given the periodic nature of the metamaterial, proper design of the unit cell requires intimate knowledge of the parameter space for each design variable. We present a detailed study of the parameter space surrounding vertical split-ring resonators and planar split-ring resonators, and demonstrate widening of the perfect absorption bandwidth based on the understanding of its parameter space.

In this paper, we report our recent findings about a first principles, multipole-based model of electric and magnetic cable braid penetrations. We consider for brevity a one-dimensional array of wires, but the model can be readily applied to realistic cable geometries. Comparisons between the first principles method and analytical formulas will be provided for both electric and magnetic penetration cases. These comparisons confirm that our first principles model works within the geometric characteristics of many commercial cables.

Optical nonlocalities are elusive and hardly observable in traditional plasmonic materials like noble and alkali metals. Here we report experimental observation of viscoelastic nonlocalities in the infrared optical response of doped cadmium-oxide, epsilon-near-zero nanofilms. The nonlocality is detectable thanks to the low damping rate of conduction electrons and the virtual absence of interband transitions at infrared wavelengths. We describe the motion of conduction electrons using a hydrodynamic model for a viscoelastic fluid, and find excellent agreement with experimental results. The electrons elasticity blue-shifts the infrared plasmonic resonance associated with the main epsilon-near-zero mode, and triggers the onset of higher-order resonances due to the excitation of electron-pressure modes above the bulk plasma frequency. We also provide evidence of the existence of nonlocal damping, i.e., viscosity, in the motion of optically-excited conduction electrons using a combination of spectroscopic ellipsometry data and predictions based on the viscoelastic hydrodynamic model., 19 pages, 5 figures

We demonstrate a fundamentally new approach of using voltage controlled quantum tunneling for modulating optical response of a metasurface coupled to intersubband transitions in semiconductor quantum wells.

We propose a cable braid electromagnetic penetration model that is based on first-principles and is derived strictly from the geometrical parameters of the cable in question. We apply this formulation to the case of a one-dimensional array of wires, which can also be modeled analytically via a multipole-conformal mapping expansion for the wire charges and is extended by means of Laplace solutions in bipolar coordinates. Both electric and magnetic penetrations are analyzed, and comparisons are performed between results from the first principles cable braid electromagnetic penetration model and those obtained using the multipole-conformal mapping expansion method. We find results in very good agreement when using up to the octopole moment (for the first principles model), covering a dynamic range of radius-to-half-spacing ratio up to 0.6. These results give us the confidence that our first principles model is applicable to the geometric characteristics of many commercial cables.

We report in this paper a first principles, multipole-based cable braid electromagnetic penetration model. We apply this formulation to the case of a one-dimensional array of wires, which can be modeled analytically via a multipole-conformal mapping expansion for the wire charges and extension by means of Laplace solutions in bipolar coordinates. We analyze both electric and magnetic penetrations and compare results from the first principles cable braid electromagnetic penetration model to those obtained using the multipole-conformal mapping expansion method. We find results in very good agreement when using up to the octopole moment (for the first principles model), covering a dynamic range of radius-to-half-spacing ratio up to 0.6. These results give us the confidence that our first principles model works within the geometric characteristics of many commercial cables.

We report a frequency-domain method based on transmission line theory that we name ATLOG — Analytic Transmission Line Over Ground — to model finite or infinite wires interacting with a conducting ground excited by an electromagnetic pulse. This method allows for the treatment of finite or infinite lossy, coated wires above a lossy ground, as well as resting on or buried beneath the ground. Comparisons with full-wave simulations strengthen the validity of the proposed method.

High-quality infrared focal plane arrays (FPAs) are used in many satellite, astronomical, and terrestrial applications. These applications require highly-sensitive, low-noise FPAs, and therefore do not benefit from advances made in low-cost thermal imagers where reducing cost and enabling high-temperature operation drive device development. Infrared detectors used in FPAs have been made for decades from alloys of mercury cadmium telluride (MCT). These infrared detectors are nearing the believed limit of their performance. This limit, known in the infrared detector community as Rule 07, dictates the dark current floor for MCT detectors, in their traditional architecture, for a given temperature and cutoff wavelength. To overcome the bounds imposed by Rule 07, many groups are working on detector compounds other than MCT. We focus on detectors employing III-V-based gallium-free In As Sb superlattice active regions while also changing the basic architecture of the pixel to improve signal-to-noise. Our architecture relies on a resonant, metallic, subwavelength nanoantenna patterned on the absorber surface, in combination with a Fabry-Perot cavity, to couple the incoming radiation into tightly confined modes near the nanoantenna. This confinement of the incident energy in a thin layer allows us to greatly reduce the volume of the absorbing layer to a fraction of the free-space wavelength, yielding a corresponding reduction in dark current from spontaneously generated electron-hole pairs in the absorber material. This architecture is detector material agnostic and could be applied to MCT detector structures as well, although we focus on using superlattice antimonide-based detector materials. This detector concept has been applied to both mid-wave (3–5 μm) and longwave (8–12 μm) infrared detectors and absorbers. Here we examine long-wave devices, as these detectors currently have a larger gap between desired device performance and that of currently existing detectors. The measured structures show an external quantum efficiency exceeding 50%. We present a comparison of the modeled and measured photoresponse of these detectors and compare these detectors to currently available commercial detectors using relevant metrics such as external quantum efficiency. We also discuss modeling of crosstalk between adjacent pixels and its influence on the potential for a dual-wavelength detector. Finally, we evaluate potential advances in these detectors that may occur in the near future.

The goal of this paper is to investigate full-wave simulations of realistic implementations of multifunctional nanoantenna enabled detectors (NEDs). We realize a 2×2 pixelated array structure that supports two wavelengths of operation. After designing each resonating structure independently using full-wave simulations with periodic boundary conditions mimicking the whole infinite array, we construct a supercell made of a 2×2 pixelated array with periodic boundary conditions mimicking the full NED. In the NED, each pixel comprises 10–20 nanoantennas. Our simulations account for the cross-talk between contiguous pixels. We observe that, even though there are finite extent effects, the pixels work as designed, each responding at the respective wavelength of operation. We want to stress that realistic simulations of multifunctional NEDs need to be performed to verify the design functionality by taking into account finite extent and cross-talk effects.

We investigate for the first time the capacity of a two-dimensional periodic array (a metasurface) of circular nanoclusters (CNCs) of plasmonic nanoparticles to support magnetic Fano resonances. These resonances are characterized by narrow angular and/or spectral features in the reflection/transmission/absorption coefficients associated with a circular disposition of nanoparticles’ dipole moments (forming a current loop) under oblique TE-polarized plane wave incidence illumination. We find that these narrow resonant features are either array-induced or single-CNC-induced, as shown by using a theoretical analysis based on the single dipole approximation and full-wave simulations, leading to enhanced magnetic and electric fields. In particular, array-induced resonances are narrower than single-CNC-induced ones and also provide even larger field enhancements, in particular generating a magnetic field enhancement of about 10-fold and an electric field enhancement of about 40-fold for a representative metasurf...

Control and manipulation of polarisation is an important topic for imaging and light matter interactions. In the infrared regime, the large wavelengths make wire grid polarisers (WGPs) a viable option, as it is possible to create periodic arrays of metallic wires at that scale. The recent advent of metamaterials has spurred an increase in non-traditional polariser motifs centred around more complicated repeat units, which potentially provide more functionality. The authors explore the use of 2D arrays of single and back-to-back vertically oriented cross dipoles arranged in a cubic in-plane silicon matrix. They show that both single and back-to-back versions have higher rejection ratios and larger bandwidths than either WGPs or 2D arrays of linear dipoles.

The development of novel thermal sources that control the emission spectrum and the angular emission pattern is of fundamental importance. In this paper, we investigate the thermal emission properties of semiconductor hyperbolic metamaterials (SHMs). Our structure does not require the use of any periodic corrugation to provide monochromatic and directional emission properties. We show that these properties arise because of epsilon-near-zero conditions in SHMs. The thermal emission is dominated by the epsilon-near-zero effect in the doped quantum wells composing the SHM. Furthermore, different properties are observed for s and p polarizations, following the characteristics of the strong anisotropy of hyperbolic metamaterials.

Metamaterial dielectric resonators represent a promising path toward low-loss metamaterials at optical frequencies. In this paper we utilize perturbations of high symmetry resonator geometries, such as cubes, either to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering and Huygens' metasurfaces, or to induce couplings between the otherwise orthogonal resonator modes to achieve high-quality factor Fano resonances. Our results are fully scalable across any frequency bands where high-permittivity dielectric materials are available, including microwave, THz, and infrared frequencies.

The ability to control the light-matter interaction with an external stimulus is a very active area of research since it creates exciting new opportunities for designing optoelectronic devices. Recently, plasmonic metasurfaces have proven to be suitable candidates for achieving a strong light-matter interaction with various types of optical transitions, including intersubband transitions (ISTs) in semiconductor quantum wells (QWs). For voltage modulation of the light-matter interaction, plasmonic metasurfaces coupled to ISTs offer unique advantages since the parameters determining the strength of the interaction can be independently engineered. In this work, we report a proof-of-concept demonstration of a new approach to voltage-tune the coupling between ISTs in QWs and a plasmonic metasurface. In contrast to previous approaches, the IST strength is here modified via control of the electron populations in QWs located in the near field of the metasurface. By turning on and off the ISTs in the semiconductor QWs, we observe a modulation of the optical response of the IST coupled metasurface due to modulation of the coupled light-matter states. Because of the electrostatic design, our device exhibits an extremely low leakage current of ∼6 pA at a maximum operating bias of +1 V and therefore very low power dissipation. Our approach provides a new direction for designing voltage-tunable metasurface-based optical modulators.

Engineering collective excitations such as plasmons and polaritons provides access to exotic optical properties. This study reports semiconductor nanostructures with coupled surface modes that interact with multiple resonant dipoles, yielding double and triple polariton branches in the system's response. This produces useful and tunable properties with the flexibility to enable low-voltage tunable filters, light-emitting diodes, and efficient nonlinear composite materials.

Thin layers of semiconductors where the permittivity crosses zero, support a particular polariton mode called epsilon-near-zero (ENZ) mode. This zero crossing can be obtained near optical phonon resonances in dielectrics or the plasma frequency in doped semiconductors. The coupling of metamaterial resonators to these ENZ modes leads to particularly large Rabi splittings. ENZ layers can be added to metamaterial-based strongly coupled systems to increase this coupling even further. I will discuss several examples of these coupled systems that include metasurfaces, phonons, intersubband transitions and ENZ modes.

Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum., Controlling light at scales smaller than its wavelength is attractive to manipulate light using small device footprints. Here, the authors propose a scheme to modify light on such small scales using a combination of metamaterial nanocavities coupled to nonlinear semiconductor heterostructures.

In this paper we describe a methodology for tailoring the design of metamaterial dielectric resonators, which represent a promising path toward low-loss metamaterials at optical frequencies. We first describe a procedure to decompose the far field scattered by subwavelength resonators in terms of multipolar field components, providing explicit expressions for the multipolar far fields. We apply this formulation to confirm that an isolated high-permittivity cube resonator possesses frequency separated electric and magnetic dipole resonances, as well as a magnetic quadrupole resonance in close proximity to the electric dipole resonance. We then introduce multiple dielectric gaps to the resonator geometry in a manner suggested by perturbation theory, and demonstrate the ability to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering by satisfying the first Kerker condition. We further demonstrate the ability to push the quadrupole resonance away from the degenerate dipole resonances to achieve local behavior. These properties are confirmed through the multipolar expansion and show that the use of geometries suggested by perturbation theory is a viable route to achieve purely dipole resonances for metamaterial applications such as wave-front manipulation with Huygens' metasurfaces. Our results are fully scalable across any frequency bands where high-permittivity dielectric materials are available, including microwave, THz, and infrared frequencies., 13 pages, 11 figures

The physics of the epsilon-near-zero (ENZ) mode, which is supported by a nanolayer at the frequency where the dielectric permittivity vanishes, has recently been a subject of debate. In this Rapid Communication, we thoroughly investigate and clarify the physics of this mode, providing its main characteristics and its domain of existence. This understanding will benefit all the applications that rely on ENZ modes in semiconductor nanolayers, including directional perfect absorption, voltage-tunable devices, and ultrafast thermal emission.

Strongly coupling metallic nanoresonators with specially designed intersubband-transitions in quantum-wells results in efficient, saturation-limited second-harmonic (SH) generation. This method also grants full control over the polarization and phase-front of the emitted SH radiation.

We use epsilon-near-zero modes in semiconductor nanolayers to design a system whose spectral properties are controlled by their interaction with multi-dipole resonances. This design flexibility renders our platform attractive for efficient nonlinear composite materials.