Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Enhanced third harmonic generation from the epsilon-near-zero modes of
  ultrathin films   We experimentally demonstrate efficient third harmonic generation from an
indium tin oxide (ITO) nanofilm (lambda/42 thick) on a glass substrate for a
pump wavelength of 1.4 um. A conversion efficiency of 3.3x10^-6 is achieved by
exploiting the field enhancement properties of the epsilon-near-zero (ENZ) mode
with an enhancement factor of 200. This nanoscale frequency conversion method
is applicable to other plasmonic materials and reststrahlen materials in
proximity of the longitudinal optical phonon frequencies.

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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: astro-ph
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The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom