Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tuning quadratic nonlinear photonic crystal fibers for zero
  group-velocity mismatch   We consider an index-guiding silica photonic crystal fiber with a triangular
air-hole structure and a poled quadratic nonlinearity. By tuning the pitch and
the relative hole size, second-harmonic generation with zero group-velocity
mismatch is found for any fundamental wavelength above 780 nm. The
phase-velocity mismatch has a lower limit with coherence lengths in the micron
range. The dimensionless nonlinear parameter is inversely proportional to the
pitch and proportional to the relative hole size. Selected cases show
bandwidths suitable for 20 fs pulse-conversion with conversion efficiencies as
high as 25%/mW.

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The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con