Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear Transfer of Intense Few Cycle Terahertz Pulse Through Opaque
  n-doped Si   Intense few cycle terahertz pulses exhibit complex non-linear behavior under
interaction with heavily n-doped Si. Fast increase in the transmission of a 700
fs pulse (central frequency 1.5 THz) through the Si sample (low field
transmission of 0:02 %) saturates at 8 % for the external field of 5 MV/cm and
then drops twofold at 20 MV/cm. An electro-optical sampling measurements
revealed formation of a single cycle terahertz pulse at this field due to
formation of a thin ionized layer by the first intense oscillation of the
terahertz field.

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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an