Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A nonlinear metasurface combining telecom-range intersubband transitions
  in GaN/AlN quantum wells with resonant plasmonic antenna arrays   We realize and investigate a nonlinear metasurface taking advantage of
intersubband transitions in ultranarrow GaN/AlN multi-quantum well
heterostructures. Owing to huge band offsets, the structures offer resonant
transitions in the telecom window around 1.55 $\mu$m. These heterostructures
are functionalized with an array of plasmonic antennas featuring
cross-polarized resonances at these near-infrared wavelengths and their second
harmonic. This kind of nonlinear metasurface allows for substantial
second-harmonic generation at normal incidence which is completely absent for
an antenna array without the multi-quantum well structure underneath. While the
second harmonic is originally radiated only into the plane of the quantum
wells, a proper geometrical arrangement of the plasmonic elements permits to
redirect the second-harmonic light to free-space radiation, which is emitted
perpendicular to the surface.

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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th