Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gouy-phase effects in the frequency combs of an optical parametric
  oscillator   We investigate the transverse mode effects on the frequency combs generated
by a type-I optical parametric oscillator (OPO) below threshold. We take the
diffraction effects fully into account, considering usual OPO architectures
instead of the self-imaging design. Further, we show that an OPO pumped with
structured light produces multiple frequency combs simultaneously,
corresponding to different combinations of spatial modes in the downconverted
fields. This result may apply to the production of hybrid multipartite
entanglement in the spatiotemporal modes of a single OPO.

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The categories of this paper are: acc-phys
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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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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: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
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The categories of this paper are: astro-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol