Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Highly asymmetric optical properties of \b{eta}-Ga2O3 as probed by
  linear and nonlinear optical excitation spectroscopy   Highly asymmetric optical properties of b-Ga2O3 are investigated by
polarization-dependent photoluminescence (PL) excitation spectroscopy for
assessing its potential use for a novel ultraviolet emitter and nonlinear
optical material. Based on power-dependent excitation and two-photon depth
scan, it is demonstrated that the underlying mechanism for the PL occurring far
below the bandgap is not caused by intrinsic polaron effects, but by excitonic
recombination at extrinsic defect sites.

28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci