Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Indication for dominating surface absorption in crystalline silicon test
  masses at 1550nm   The sensitivity of future gravitational wave (GW) observatories will be
limited by thermal noise in a wide frequency band. To reduce thermal noise, the
European GW observatory Einstein GW Telescope (ET) is suggested to use
crystalline silicon test masses at cryogenic temperature and a laser wavelength
of 1550nm. Here, we report a measurement of the optical loss in a prototype
high-resistivity crystalline silicon test mass as a function of optical
intensity at room temperature. The total loss from both the bulk crystal and
the surfaces was determined in a joint measurement. The characterization window
ranged from small intensities below 1W/cm^2, as planned to be used in ET, up to
21kW/cm^2. A non-linear absorption was observed for intensities above a few
kW/cm^2. In addition we have observed an intensity-independent offset that
possibly arises from absorption in the crystal surfaces. This absorption was
estimated to approx. 800 ppm/surface, which might be too high for a cryogenic
operation of a fibre-suspended silicon test mass. Such an offset was not
observed in other recent measurements that were insensitive to surface
absorption. Finally, a set of further characterization measurements is proposed
to clearly separate the contributions from the surfaces and the bulk crystal.

8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn