Group‐Velocity‐Controlled and Gate‐Tunable Directional Excitation of Polaritons in Graphene‐Boron Nitride Heterostructures

Jiang, Yuyu; Lin, Xiao; Low, Tony; Zhang, Baile; Chen, Hongsheng

doi:10.1002/lpor.201800049

Cited by 60 publications

(37 citation statements)

References 35 publications

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“…The surface conductivity of graphene can be tuned over a wide range by electrical biasing in a parallel capacitor configuration which leads to a change in the Fermi energy level via field-effect. A monolayer graphene sheet can support highly confined surface plasmon polaritons (SPPs) which provides an ideal platform for tunable manipulation of guided light at nanoscale [52][53][54]. Moreover, incorporation of graphene in resonant structures can yield a large tunability in the optical response of metasurfaces via enhanced light-graphene interactions.…”

Section: Implementation Based On Graphene-wrapped Microwiresmentioning

confidence: 99%

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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Modulation of metasurfaces in time gives rise to several exotic space-time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a timemodulated metasurface which is linearly proportional to the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonant regime. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2π span in the wavefronts of generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Teraherz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links with large isolations via modulationinduced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.

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Section: Implementation Based On Graphene-wrapped Microwiresmentioning

confidence: 99%

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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“…It has also recently been shown to host point defects that function as bright, room temperature single photon sources, which can enable technologies such as quantum cryptography and precision sensing [14,15]. On top of these potential applications, the strong electron-phonon coupling and hyperbolic dispersion of hBN make it an exciting platform to study rich new physical phenomena such as phonon-polaritons and the effects of isotopes [12,[16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Rotationally aligned hexagonal boron nitride on sapphire by high-temperature molecular beam epitaxy

Page

Casamento

Cho

et al. 2019

Phys. Rev. Materials

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Hexagonal boron nitride (hBN) has been grown on sapphire substrates by ultrahigh-temperature molecular beam epitaxy (MBE). A wide range of substrate temperatures and boron fluxes have been explored, revealing that high crystalline quality hBN layers are grown at high substrate temperatures, >1600℃ , and low boron fluxes, ∼1 × 10 %& Torr beam equivalent pressure. In situ reflection high-energy electron diffraction revealed the growth of hBN layers with 60° rotational symmetry and the [112 + 0] axis of hBN parallel to the [11 + 00] axis of the sapphire substrate. Unlike the rough, polycrystalline films previously reported, atomic force microscopy and transmission electron microscopy characterization of these films demonstrate smooth, layered, few-nanometer hBN films on a nitridated sapphire substrate. This demonstration of high-quality hBN growth by MBE is a step toward its integration into existing epitaxial growth platforms, applications, and technologies.

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“…The nonlinear photonic graphene not only represents a flexible, lossless approach for achieving strong optical chirality, but also provides a dynamically tunable and reconfigurable approach of Dirac dispersions. Our results may open up a new way to manipulate the valley‐dependent effects in photonic graphene and offer an alternative route to realizing dynamic manipulation of spin and tailoring the light–matter interaction such as controlling group velocity of plasmons or the motion velocity of source …”

Section: Resultsmentioning

confidence: 97%

Pseudospin‐Mediated Optical Spin–Spin Interaction in Nonlinear Photonic Graphene

Guan

Shi

Liu

et al. 2018

Laser & Photonics Reviews

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Dynamic manipulation of the spin of photons is important for many applications ranging from optical sensing to optical information processing. In the past, the study on controlling the spin of light has focused on chiral materials, three‐dimensional structures lacking any mirror symmetries. However, the complexity of fabrication of such structures has hindered their practical applications. In this work, the dynamic switching of optical chirality in two‐dimensional honeycomb photonic crystal—the so‐called photonic graphene is explored. In particular, optical spin–spin interaction mediated by the pseudospin states of the photonic graphene is proposed. A circularly polarized pumping beam can lift the degeneracy at the Dirac cones, leading to chiral responses for a probe beam incident along the direction of the Dirac points. Interestingly, the chirality is determined by the both the valley index and the spin of the pumping beam. The proposed nonlinear photonic graphene offers a new route to manipulate valley‐ and spin‐dependent phenomena in 2D photonic systems.

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Group‐Velocity‐Controlled and Gate‐Tunable Directional Excitation of Polaritons in Graphene‐Boron Nitride Heterostructures

Cited by 60 publications

References 35 publications

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

Rotationally aligned hexagonal boron nitride on sapphire by high-temperature molecular beam epitaxy

Pseudospin‐Mediated Optical Spin–Spin Interaction in Nonlinear Photonic Graphene

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