Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Transverse mode instability and thermal effects in thulium-doped fiber
  amplifiers under high thermal loads   We experimentally analyze the average-power-scaling capabilities of
ultrafast, thulium-doped fiber amplifiers. It has been theoretically predicted
that thulium-doped fiber laser systems, with an emission wavelength around 2
um, should be able to withstand much higher heat-loads than their Yb-doped
counterparts before the onset of transverse mode instability (TMI) is observed.
In this work we experimentally verify this theoretical prediction by operating
thulium doped fibers at very high heat-load. In separate experiments we analyze
the performance of two different large-core, thulium-doped fiber amplifiers.
The first experiment aims at operating a short, very-large core, thulium-doped
fiber amplifier at extreme heat-load levels of more than 300 W/m. Even at this
extreme heat-load level, the onset of TMI is not observed. The second
experiment maximizes the extractable average-output power from a large-core,
thulium-doped, fiber amplifier. We have achieved a pump-limited average output
power of 1.15 kW without the onset of TMI. However, during a longer period of
operation at this power level the amplifier performance steadily degraded and
TMI could be observed for average powers in excess of 847 W thereafter. This is
the first time, to the best of our knowledge, that TMI has been reported in a
thulium-doped fiber amplifier.

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The categories of this paper are: stat
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn