Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase matching alters spatial multiphoton processes in dense atomic
  ensembles   Multiphoton processes in dense atomic vapors such as four-wave mixing or
coherent blue light generation are typically viewed from single-atom
perspective. Here we study the surprisingly important effect of phase matching
near two-photon resonances that arises due to spatial extent of the atomic
medium within which the multiphoton process occurs. The non-unit refractive
index of the atomic vapor may inhibit generation of light in nonlinear
processes, significantly shift the efficiency maxima in frequencies and
redirect emitted beam. We present these effects on an example of four-wave
mixing in dense rubidium vapors in a double-ladder configuration. By deriving a
simple theory that takes into account essential spatial properties of the
process, we give precise predictions and confirm their validity in the
experiment. The model allows us to improve on the geometry of the experiment
and engineer more efficient four-wave mixing.

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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: cs
10
The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: astro-ph
2
The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: cmp-lg
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The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th