Imaging of Anomalous Internal Reflections of Hyperbolic Phonon-Polaritons in Hexagonal Boron Nitride

Giles, Alexander J.; Dai, Siyuan; Glembocki, O. J.; Kretinin, A. V.; Sun, Zhiyuan; Ellis, Chase T.; Tischler, Joseph G.; Taniguchi, Takashi; Watanabe, Kenji; Fogler, M. M.; Новоселов, К. С.; Basov, D. N.; Caldwell, Joshua D.

doi:10.1021/acs.nanolett.6b01341

Cited by 112 publications

(130 citation statements)

References 42 publications

(93 reference statements)

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“…Inside the h-BN waveguide, we recognize ‘zig-zag' patterns. They manifest HP rays that emerge from corners214647 and reflect at the top and bottom h-BN waveguide surfaces48. As the propagation angle, θ , of the hyperbolic rays depends on the frequency ω (given by21 , the multiple reflections yield complex and frequency-dependent field distributions inside the waveguide, which extend several nanometres above the top waveguide surface.…”

Section: Resultsmentioning

confidence: 99%

Nanoimaging of resonating hyperbolic polaritons in linear boron nitride antennas

et al. 2017

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Polaritons in layered materials—including van der Waals materials—exhibit hyperbolic dispersion and strong field confinement, which makes them highly attractive for applications including optical nanofocusing, sensing and control of spontaneous emission. Here we report a near-field study of polaritonic Fabry–Perot resonances in linear antennas made of a hyperbolic material. Specifically, we study hyperbolic phonon–polaritons in rectangular waveguide antennas made of hexagonal boron nitride (h-BN, a prototypical van der Waals crystal). Infrared nanospectroscopy and nanoimaging experiments reveal sharp resonances with large quality factors around 100, exhibiting atypical modal near-field patterns that have no analogue in conventional linear antennas. By performing a detailed mode analysis, we can assign the antenna resonances to a single waveguide mode originating from the hybridization of hyperbolic surface phonon–polaritons (Dyakonov polaritons) that propagate along the edges of the h-BN waveguide. Our work establishes the basis for the understanding and design of linear waveguides, resonators, sensors and metasurface elements based on hyperbolic materials and metamaterials.

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Section: Resultsmentioning

confidence: 99%

Nanoimaging of resonating hyperbolic polaritons in linear boron nitride antennas

et al. 2017

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“…One broad implication of our work is that nanoimaging of collective modes can reveal nontrivial electron properties, in this case, 1D bound states. Recent experiments have demonstrated that this technique is not limited to plasmons or graphene or 2D systems [27][28][29][30] . We hope that our work stimulates even wider use of this novel spectroscopic tool.…”

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confidence: 99%

Tunable Plasmonic Reflection by Bound 1D Electron States in a 2D Dirac Metal

Jiang

Pan

et al. 2016

Phys. Rev. Lett.

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We show that surface plasmons of a two-dimensional Dirac metal such as graphene can be reflected by line-like perturbations hosting one-dimensional electron states. The reflection originates from a strong enhancement of the local optical conductivity caused by optical transitions involving these bound states. We propose that the bound states can be systematically created, controlled, and liquidated by an ultranarrow electrostatic gate. Using infrared nanoimaging, we obtain experimental evidence for the locally enhanced conductivity of graphene induced by a carbon nanotube gate, which supports this theoretical concept.Plasmon scattering and plasmon losses in Dirac materials, such as graphene and topological insulators, are problems of interest to both fundamental and applied research. It is an outstanding challenge to understand various kinds of interaction (electron-electron, electron-phonon, electron-photon, electron-disorder) responsible for these complex phenomena [1][2][3][4][5] . At the same time, control of plasmon scattering is critical if this class of materials is to become a new platform for nanophotonics [6][7][8][9] .One source of plasmon scattering is long-range inhomogeneity of the electron density, which causes local fluctuations in the plasmon wavelength λ p . If the inhomogeneities are weak, those of size comparable to the average λ p are expected to be the dominant scatterers 10,11 Surprisingly, recent experiments have revealed that one-dimensional (1D) defects of nominally atomic width can act as effective reflectors for plasmons with wavelengths as large as a few hundred nm. Strong plasmon reflection was observed near grain boundaries 12,13 , topological stacking faults 14 , as well as nanometerscale wrinkles and cracks 11,12 in graphene. If this anomalous reflection is indeed an ubiquitous effect largely unrelated to the specific nature of a defect, it calls for a universal explanation. In this Letter we attribute its origin to electron bound states commonly occurring near 1D defects. We show that optical transitions involving the bound states can produce strong dissipation at small distances x from the defect and therefore, alter plasmon dynamics. To support this idea we present a theoretical analysis of an exactly solvable model, which illustrates qualitative and quantitative characteristics of the bound states and predicts how their optical response depends on the tunable parameters of a 1D potential well. We also report an attempt to probe the predicted effects experimentally. Our approach is to employ an ultranarrow electric gate in the form of a carbon nanotube (CNT) to create a precisely tunable 1D barrier in graphene. This device enables a systematic investigation and control of plasmon propagation, including, in principle, an implementation of a plasmon on-off switch (Fig. 1). What we find is that the measured real-space profile of the plasmon amplitude (Fig. 4) cannot be accounted for by a local change in λ p alone. Instead, the data are consistent with the presence of an enhanced ...

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“…Similar to graphene nanoresonators discussed in Section , the localized hyperbolic phonon polariton modes can be excited in patterned polar van der Waals crystals . In patterned h‐BN, hyperspectral resonances with Q‐factors of 283 could be achieved due to the absence of electronic losses in h‐BN .…”

Section: Molecular Sensingmentioning

confidence: 88%

Functional Mid‐Infrared Polaritonics in van der Waals Crystals

Kim

Menabde

Brar

et al. 2019

Advanced Optical Materials

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Despite high scientific and technological potential, nanophotonics research in the mid‐infrared regime remains relatively less explored compared to other frequency bands, largely because the mid‐infrared requires a totally different set of optical materials. Polaritons in layered 2D materials, or van der Waals (vdW) crystals, provide a new set of building blocks for mid‐infrared nanophotonics. Herein, the recently reported polaritonic properties of various vdW crystals are summarized in the context of their mid‐infrared applications. Both polaritons in vdW crystals with naturally anisotropic atomic structures as well as tunable plasmon polaritons in vdW semimetals are discussed. The extreme field confinement of 2D polaritons (confinement factors ≈100) enhances both their radiative heat transfer as well as the optical coupling to the vibrational modes of molecules, allowing for highly sensitive chemical detection. Their tunable properties, meanwhile, enable dynamic modulation of mid‐infrared light to realize dynamic phase shifters, mid‐infrared modulators, and spectrally tunable thermal emitters. By vertically stacking vdW crystals, it is possible to create a large variety of new effective materials with substantially different polaritonic properties compared to their building blocks.

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Imaging of Anomalous Internal Reflections of Hyperbolic Phonon-Polaritons in Hexagonal Boron Nitride

Cited by 112 publications

References 42 publications

Nanoimaging of resonating hyperbolic polaritons in linear boron nitride antennas

Nanoimaging of resonating hyperbolic polaritons in linear boron nitride antennas

Tunable Plasmonic Reflection by Bound 1D Electron States in a 2D Dirac Metal

Functional Mid‐Infrared Polaritonics in van der Waals Crystals

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