Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Design of an optical reference cavity with low thermal noise and
  flexible thermal expansion properties   An ultrastable optical reference cavity with re-entrant fused silica mirrors
and a ULE spacer structure is designed through finite element analysis. The
designed cavity has a low thermal noise limit of $1\times10^{-16}$ and a
flexible zero crossing temperature of the effective coefficient of thermal
expansion (CTE). The CTE zero crossing temperature difference between a
composite cavity and a pure ULE cavity can be tuned from $-10\ ^{\circ}$C to
$23\ ^{\circ}$C, which enables operation of the designed reference cavity near
room temperature without worrying about the CTE zero crossing temperature of
the ULE spacer. The design can be applied to cavities with different lengths.
Vibration immunity of the cavity is also achieved through structure
optimization.

31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio