Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 1.26 $\mu$m intersubband transitions in In$_{0.3}$Ga$_{0.7}$As/AlAs
  quantum wells   We observed room-temperature intersubband transitions at 1.26 microns in
n-doped type-II In$_{0.3}$Ga$_{0.7}$As/AlAs strained quantum wells. An improved
tight-binding model was used to optimize the structure parameters in order to
obtain the shortest wavelength intersubband transition ever achieved in a
semiconductor system. The corresponding transitions occur between the first
confined electronic levels of the well following mid-infrared optical pumping
of electrons from the barrier X-valley into the well ground state.

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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
9
The categories of this paper are: nlin
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The categories of this paper are: econ
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: astro-ph
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The categories of this paper are: acc-phys