Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A mid-infrared biaxial hyperbolic van der Waals crystal   Hyperbolic media have attracted much attention in the photonics community,
thanks to their ability to confine light to arbitrarily small volumes and to
their use for super-resolution applications. The 2D counterpart of these media
can be achieved with hyperbolic metasurfaces, which support in-plane hyperbolic
guided modes thanks to nanopatterns which, however, pose significant
fabrication challenges and limit the achievable confinement. We show that thin
flakes of the van der Waals material {\alpha}-MoO3 can support naturally
in-plane hyperbolic polariton guided modes at mid-infrared frequencies without
any patterning. This is possible because {\alpha}-MoO3 is a biaxial hyperbolic
crystal, with three different Restrahlen bands, each for a different crystal
axis. Our findings can pave the way towards new paradigm to manipulate and
confine light in planar photonic devices.

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The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th