Phonon-polaritonics: enabling powerful capabilities for infrared photonics

Abstract

Here, we review the progress and most recent advances in phonon-polaritonics, an emerging and growing field that has brought about a range of powerful possibilities for mid- to far-infrared (IR) light. These extraordinary capabilities are enabled by the resonant coupling between the impinging light and the vibrations of the material lattice, known as phonon-polaritons (PhPs). These PhPs yield a characteristic optical response in certain materials, occurring within an IR spectral window known as the reststrahlen band. In particular, these materials transition in the reststrahlen band from a high-refractive-index behavior, to a near-perfect metal behavior, to a plasmonic behavior – typical of metals at optical frequencies. When anisotropic they may also possess unconventional photonic constitutive properties thought of as possible only with metamaterials. The recent surge in two-dimensional (2D) material research has also enabled PhP responses with atomically-thin materials. Such vast and extraordinary photonic responses can be utilized for a plethora of unusual effects for IR light. Examples include sub-diffraction surface wave guiding, artificial magnetism, exotic photonic dispersions, thermal emission enhancement, perfect absorption and enhanced near-field heat transfer. Finally, we discuss the tremendous potential impact of these IR functionalities for the advancement of IR sources and sensors, as well as for thermal management and THz-diagnostic imaging.

Tunable plasmon-phonon polaritons in anisotropic 2D materials on hexagonal boron nitride

“…The flat-land optics of in-plane anisotropic polaritons can also be realized with phononic metasurfaces, where photons and optical phonons of polar dielectrics (such as SiC and hexagonal boron nitride, hBN [31,32]) are coupled into phonon polaritons. hBN is a uniaxially anisotropic ε hBN diag(ε t , ε t , ε z ) polar Van der Waals (VdW) material that shows hyperbolic characteristics inside its Reststrahlen (RS) bands in the mid-infrared (MIR) region while acting as a typical anisotropic medium outside of these bands [33,34].…”

Polariton panorama

“…Fuchs-Kliewer interface polaritons: phonon polaritons occurring at surfaces and interfaces [183] with the matter part are originating from Fuchs-Kliewer surface phonons [184]. Huber et al [185] employed nanoinfrared methods to visualize propagating Fuchs-Kliewer surface phonon polaritons in SiC.…”

Macroscopic QED for quantum nanophotonics: emitter-centered modes as a minimal basis for multiemitter problems

“…[64], but can break down otherwise. In general, this happens for coupling to evanescent fields [65] and in particular when subwavelength confinement is used to generate extremely small effective mode volumes, such as in plasmonic [66,67] or phonon-polaritonic systems [68,69]. This observation is particularly relevant as such subwavelength confinement is the only possible strategy for obtaining large enough light-matter coupling strengths to approach the single-emitter strong coupling regime at room temperature [70][71][72][73].…”