Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Long-period fiber grating as wavelength selective element in double-clad
  Yb-doped fiber-ring lasers   Selection of operating wavelength of the Yb-doped fiber-ring lasers using
longperiod fiber gratings (LPFGs) is suggested. In the proposed method,
customized LPFG that sustains high powers serves as a broad-band rejection
filter. It modifies the net gain profile of the laser, enabling the peak gain
to occur at a designed wavelength. Spectral range of oscillation between
1050-1110 nm was experimentally demonstrated. This range can be extended to
both shorter and longer wavelengths with proper design of the LPFG and length
of the Yb-doped fiber. The gratings were inscribed by CO2 laser and the grating
period down to 175 ?m was achieved being, to our best knowledge, the shortest
reported LPFG period using this technique.

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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: astro-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th