Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Polarization maintaining large mode area photonic crystal fiber   We report on a polarization maintaining large mode area photonic crystal
fiber. Unlike, previous work on polarization maintaining photonic crystal
fibers, birefringence is introduced using stress applying parts. This has
allowed us to realize fibers, which are both single mode at any wavelength and
have a practically constant birefringence for any wavelength. The fibers
presented in this work have mode field diameters from about 4 to 6.5 micron,
and exhibit a typical birefringence of 1.5e-4.

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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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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: q-bio
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph