Hyperbolic Metamaterials and Metasurfaces: Fundamentals and Applications

Abstract

and their potential applications in various fields, including optical waveguiding, imaging, ultrasensitive optical sensing, and electromagnetic cloaking.Among the different types of optical metamaterials proposed and demonstrated to date, there is one class of highly anisotropic metamaterials which exhibit hyperbolic (or indefinite) dispersions, depending on their effective electric tensors (here, we only consider nonmagnetic media with unit magnetic tensors). Such hyperbolic metamaterials (HMMs) have reached the ultra-anisotropic limit of traditional uniaxial crystal and lead to dramatic changes for the light propagation behaviors. [12][13][14][15][16] Compared with other optical metamaterials, like chiral [17,18] and split ring resonator-based metamaterials, [19,20] HMMs have advantages of relative ease of fabrication at optical frequencies, broadband nonresonant and 3D bulk responses, and flexible wavelength tunability. As a result, HMMs have attracted widespread interest and become a good multifunctional platform for many exotic applications, such as optical negative refraction and light beam steering, [12,[21][22][23][24][25][26][27][28] subdiffraction-limited imaging and nanolithography, [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] spontaneous and thermal emission engineering, [71][72][73][74][75][76][77][78][79][80] ultrasensitive optical, biological, and chemical sensing, [81][82][83][84][85][86][87][88][89] omnidirectional and broadband optical absorption. [90][91][92][93] On the other hand, ultrathin metasurfaces, which comprise a class of planar optical metamaterials with many subwavelength structural units, have attracted much attention due to their ability of locally controlling the phase, amplitude, and polarization of light at the interface between two natural materials. [94][95][96][97] 2D planar metasurfaces have many advantages over bulk metamaterials, including simplifying the fabrication and integration process, reducing energy loss, and being compatible with other photonics devices. In this context, as an efficient surface wave modulation platform, hyperbolic metasurfaces (HMSs) with in-plane hyperbolic dispersions have a potential influence on the development of on-chip planar photonic devices. [95,98] In this review, we first discuss the dispersions and realizations of hyperbolic media. Then, we review the recent achievements of various optical applications based on 3D bulk HMMs and 2D planar HMSs. It should be stressed that, although some application scenarios for 3D HMMs and 2D HMSs are analogous, in fact they are not equal to each other because additional constrains will be introduced on the surface wave as the dimensionality degraded, which is accompanied by fancy in-plane Recent advances in nanofabrication and characterization technologies have spurred many breakthroughs in the field of optical metamaterials and metasurfaces that provide novel ways of manipulating light interaction in a well controllable manner. Among these artificial nanostructured materials, ...

The Optical Properties and Plasmonics of Anisotropic 2D Materials

“…Plasmons in 2D materials with in‐plane anisotropy have recently attracted increasing attention due to the possibility of realizing in‐plane hyperbolic plasmon polaritons, the iso‐frequency contour of which is a hyperbola . Such special dispersion topology supports directional propagating polaritons with divergent densities of states, which enables a series of potential applications in nanophotonics . However, no experiment is reported to have observed the hyperbolic plasmons in the natural 2D vdWs surface.…”

“…Fascinatingly, the hyperbolic plasmon polaritons, whose iso‐frequency contour is a hyperbola, are predicted to naturally exist in BP films, which originate from the coupling between the intraband and interband optical conductivity . This special plasmon topology leads to an anomalously large photonic density of states and directional propagating plasmonic rays, which promises intriguing applications for planar photonics . Moreover, the tunability of the band structure by electrical gating and strain in BP and the possibility of forming heterostructures with other 2D materials make the plasmon in BP exhibit several unique potential applications that cannot be realized in metasurfaces composed of artificial structures .…”

Collective photonic response of high refractive index dielectric metasurfaces

“…Nanostructures with sub-wavelength periodicities and profiles are today explored as a major route for controlling the flow-of-light 1 , 2 . Metallic structures incident with plane electromagnetic waves in the sub-wavelength regime give rise to electromagnetic responses like effective negative refractive index 3 , perfect absorption 4 , perfect magnetic mirrors 5 , 6 , optical chirality 7 and sub-diffraction limited imaging 8 , 9 .…”

Controlling the plasmon resonance via epsilon-near-zero multilayer metamaterials

“…The HMM substrates used in this study are composed of three bilayers of Au and titanium dioxide (TiO 2 ). The optical properties of these metamaterials are modelled by the effective medium theory (EMT) [30,[33][34][35][36][37][38]. The HMM serves as a uniaxial medium with permittivity given by a tensor ε [ε xx , ε yy , ε zz ], where in-plane isotropic/parallel components are defined as ε xx ε yy ε ∥ .…”