Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 10^{-7} contrast ratio at 4.5Lambda/D: New results obtained in
  laboratory experiments using nano-fabricated coronagraph and multi-Gaussian
  shaped pupil masks   We present here new experimental results on high contrast imaging of 10^{-7}
at 4.5Lambda/D (Lambda = 0.820 microns) by combining a circular focal plane
mask (coronagraph) of 2.5Lambda/D diameter and a multi-Gaussian pupil plane
mask. Both the masks were fabricated on very high surface quality (Lambda/30)
BK7 optical substrates using nano-fabrication techniques of photolithography
and metal lift-off. This process ensured that the shaped masks have a useable
edge roughness better than Lambda/4 (rms error better than 0.2 microns), a
specification that is necessary to realize the predicted theoretical limits of
any mask design. Though a theoretical model predicts a contrast level of
10^{-12}, the background noise of the observed images was speckle dominated
which reduced the contrast level to 4x10^{-7} at 4.5Lambda/D. The optical setup
was built on the University of Illinois Seeing Improvement System (UnISIS)
optics table which is at the Coude focus of the 2.5-m telescope of the Mt.
Wilson Observatory. We used a 0.820 micron laser source coupled with a 5 micron
single-mode fiber to simulate an artificial star on the optical test bench of
UnISIS.

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The categories of this paper are: funct-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
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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: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc