Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Generation of high-quality terahertz OAM mode based on soft-aperture
  difference frequency generation   We demonstrate the generation of high-quality tunable terahertz (THz)
vortices in an eigenmode by employing soft-aperture difference frequency
generation of a vortex output and a Gaussian mode. The generated THz vortex
output exhibits a high-quality orbital angular momentum (OAM) mode with a
topological charge of $\ell_{THz}=\pm1$ in a frequency range of 2-6 THz. The
maximum average power of the THz vortex output obtained was ~3.3 $\mu$W at 4
THz.

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The categories of this paper are: cmp-lg
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: q-alg