Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral characterization of a frequency comb based on cascaded
  quadratic nonlinearities inside an optical parametric oscillator   We present an experimental study of optical frequency comb generation based
on cascaded quadratic nonlinearities inside a continuous-wave-pumped optical
parametric oscillator. We demonstrate comb states which produce
narrow-linewidth intermode beat note signals, and we verify the mode spacing
uniformity of the comb at the Hz level. We also show that spectral quality of
the comb can be improved by modulating the parametric gain at a frequency that
corresponds to the comb mode spacing. We have reached a high average output
power of over 4 W in the near-infrared region, at ~2 {\mu}m.

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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
1
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: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
5
The categories of this paper are: gr-qc
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat