Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spatio-Temporal Supermodes:Rapid Reduction of Spatial Coherence in
  Highly Multimode Lasers   Spatial coherence quantifies spatial field correlations over time, and is one
of the fundamental properties of light. Here we investigate the spatial
coherence of highly multimode lasers in the regime of short time scales.
Counter intuitively, we show that in this regime, the temporal (longitudinal)
modes play a crucial role in spatial coherence reduction. To evaluate the
spatial coherence we measured the temporal dynamics of speckle fields generated
by a highly multimode laser with over $10^5$ lasing spatial (transverse) modes,
and examined the dependence of speckle contrast on the exposure time of the
detecting device. We show that in the regime of short time scale, the spatial
and temporal modes interact to form spatio-temporal supermodes, such that the
spatial degrees of freedom are encoded onto the temporal modes. As a result,
the speckle contrast depends on the number of temporal modes, and the degree of
spatial coherence is reduced and the speckle contrast is suppressed. In the
regime of long times scale, the supermodes are no longer a valid representation
of the laser modal structure. Consequently, the spatial coherence is
independent of the temporal modes, and the classical result, where the speckle
contrast is suppressed as the number of spatial modes, is obtained. Due to this
new spatio-temporal mechanism, highly multimode lasers can be used for speckle
suppression in high-speed full-field imaging applications, as we demonstrate
here for imaging of a fast moving object.

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The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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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: econ
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ph