Van der Waals (vdW) materials are at the core of modern optoelectronics and nanophotonics. However, relatively limited research attention is devoted to their giant optical anisotropy. Here, we demonstrate that the use of giant anisotropy leads to the next-generation integrated circuits and optical elements, determining the exact values of anisotropic dielectric permittivity tensor for the variety of vdW materials in the broad spectral range (250–1700 nm) using cross-validation of far- and near-field techniques, accompanied by first-principle calculations. Our results show high refractive index, transparency over the whole studied spectral range and giant optical anisotropy for all investigated vdW materials. Furthermore, we suggest applications of vdW materials for chiral optics and integrated photonics.
Strongly anisotropic media where principal components of the dielectric tensor have opposite signs are called hyperbolic. These materials permit highly directional, volume-confined propagation of slow-light modes at deeply sub-diffractional size scales, leading to unique nanophotonic phenomena. The realization of hyperbolic materials within the optical spectral range has been achieved primarily through the use of artificial structures typically composed of plasmonic metals and dielectric constituents. However, while proof-of-principle experiments have been performed, the high plasmonic losses and inhomogeneity of the structures limit most advances to the laboratory. Recently, hexagonal boron nitride (hBN) was identified as a natural hyperbolic material (NHM), offering a low-loss, homogeneous medium that can operate in the mid-infrared. We have exploited the NHM response of hBN within periodic arrays of conical nanoresonators to demonstrate ‘hyperbolic polaritons,’ deeply sub-diffractional guided waves that propagate through the volume rather than on the surface of a hyperbolic material. We have identified that the polaritons are manifested as a four series of resonances in two distinct spectral bands that have mutually exclusive dependencies upon incident light polarization, modal order, and aspect ratio. These observations represent the first foray into creating NHM building blocks for mid-infrared to terahertz nanophotonic and metamaterial devices. This talk will also discuss potential near-term applications stemming from these developments.
We report the suppression of the Hall effect in a mesoscopic Hall cross with a strong magnetic field only in the center and vanishingly small outside. The local magnetic field is produced by placing Dy pillar on top of a structure with high-mobility two-dimensional electron gas (2DEG). The effect is found to be due to a sharp increase of the number of back-scattered and quasi-localized electron orbits. The possibility of localizing electrons inside the magnetic inhomogeneity region is discussed.
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