Coherent perfect absorption in epsilon-near-zero metamaterials

Abstract

Above-light-line surface plasmon polaritons can arise at the interface between a metal and ǫ-near-zero metamaterial. This unique feature induces unusual fast-wave non-radiative modes in a ǫ-near-zero material/metal bilayer. Excitation of this peculiar mode leads to wide-angle perfect absorption in low-loss ultrathin metamaterials. The ratio of the perfect absorption wavelength to the thickness of the ǫ-near-zero metamaterial can be as high as 10 4 ; the electromagnetic energy can be confined in a layer as thin as λ/10000. Unlike conventional fast-wave leaky modes, these fast-wave non-radiative modes have quasi-static capacitive features that naturally match with the space-wave field, and thus are easily accessible from free space. The perfect absorption wavelength can be tuned from mid-to far-infrared by tuning the ǫ ≈ 0 wavelength while keeping the thickness of the structure unchanged. PACS numbers: 42.25.Bs, 78.67.Pt, 42.82.Et A metamaterial is a composite structure with an electromagnetic (EM) response not readily observed in naturally occurring materials. Many remarkable phenomenon have been predicted [1][2][3][4] by tuning the permittivity ǫ and permeability µ in extraordinary ways. If the dielectric response is made vanishingly small, creating an epsilon-near-zero (ENZ) material, interesting radiative effects are expected to occur [5][6][7]. On the other hand, by manipulating the EM response to achieve a small transmittance (T ) and reflectance (R), enhanced absorption can ensue. Strong absorption in a thin layer typically requires high loss. One of the earliest absorbers, the Salisbury screen [8], is based on the phenomenon of destructive wave interference, and is thus limited to a minimum thickness of one quarter wavelength. To overcome the thickness constraint, absorbing screens using metamaterials [9] and high impedance ground planes [10] have recently been proposed. By exploring resonant enhancement, thin metamaterial and nanoplasmonic absorbers were demonstrated in structures having localized resonances [11][12][13][14][15][16][17][18][19][20][21][22][23]. In those structures, the geometrical quality factor (GQF), i.e. the ratio of the perfect absorption wavelength to the thickness of the medium, is significantly improved compared to the standard Salisbury screen. The best GQF of those structures is about 40 [14].Based on a fundamentally different mechanism, in this paper we demonstrate wide-angle perfect absorption in a lowloss ultrathin ENZ-metamaterial/metal bilayer as shown in Fig. 1. In our structure, the GQF can be as high as 10 4 . This structure possesses fast-wave non-radiative (FWNR) modes due to unconventional above-light-line surface plasmon polaritons (ALL-SPPs) at the ENZ-metal interface, which is easily accessible from free space. Fast waves have phase velocities exceeding the speed of light in vacuum. Conventional fast waves in planar structures are radiative leaky modes that cannot be excited by plane wave incidence due to wave-vector mismatch at the boundary. For our ENZ-metal st...

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

“…Moreover, ENZ may be synthesized at virtually any frequency with properly designed metamaterials, using subwavelength arrangements of plasmonic resonators or using guided modes and operating near the cutoff frequency. Many optical effects and potential applications arising from ENZ behavior have been proposed or demonstrated including optical tunneling [14][15][16] , phase patterning 17 , directional emission 18 , perfect absorption 19,20 , dielectric sensing 21 , guided index lensing 22 , enhanced emission [23][24][25] , optical cloaking 26 , strong coupling phenomena [27][28][29] , optical modulation 30,31 , thermo-photovoltaics 32 , and enhanced optical nonlinearities [33][34][35] .…”

Perfect absorption and no reflection in disordered photonic crystals

“…where we have phenomenologically introduced the dephasing rates γ ij with the assumption γ 13 = γ 14 = γ γ 12 . Note that the dressing field comprises a red-detuned traveling-wave (TW) component and a blue-detuned standing-wave (SW) component so as to yield a small space-dependent dynamic shift [43], mismatch between the optical lattice (black solid curve) and the space-periodic dynamic shift δ ds (z) (red dashed curve) arising, respectively, from the dipole-trap beams and from the dressing field beams.…”

“…Among them, unidirectional reflectionless (URL) media [1][2][3], where reflection from one side is significantly suppressed, and coherent perfect absorption (CPA) media [4][5][6][7][8][9][10], where the two-sided incident waves are completely quenched, are extensively studied wave phenomena, especially in optics [6,[9][10][11][12][13][14][15][16][17]. On-chip implementation of URL media, e.g., is expected to underpin a new generation of photonic devices [18], while CPA media clearly provides an additional flexibility to tune absorption when compared to perfect one-port absorbers.…”

Resonant absorption of electromagnetic waves in transition anisotropic media

“…More recently, hyperbolic media, where one of the principal values of the permittivity tensor has a different sign from the others and their dispersion surface is a hyperboloid, have attracted great interest from many researchers [24][25][26]. The strong absorption of EM waves in uniform anisotropic media has been studied recently by several authors, with an emphasis on the role of a hyperbolic dispersion relation [9][10][11][12][13][14]. In this paper, we consider an inhomogeneous slab of a stratified anisotropic medium, optical axes of which are tilted with respect to the direction of inhomogeneity.…”

“…In recent years, there have been many studies on the strong absorption of electromagnetic (EM) waves occurring in media with near-zero effective dielectric permittivity ǫ, termed epsilon-nearzero media, and in transition metamaterials inside which ǫ varies continuously from positive to negative values, passing through a narrow resonance region where the real part of ǫ is identically zero [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In the presence of an infinitesimally small amount of damping in the resonance region, a large absorption of the EM wave energy occurs.…”