Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extraction of absorption coefficients from GaN nanowires grown on opaque
  substrates   We demonstrate a new method to measure absorption coefficients in any family
of nanowires, provided they are grown on a substrate having considerable
difference in permittivity with the nanowire-air matrix. In the case of high
crystal quality, strain-free GaN nanowires, grown on Si (111) substrates with a
density of ~1010 cm-2, the extracted absorption coefficients do not exhibit any
enhancement compared to bulk GaN values, unlike relevant claims in the
literature. This may be attributed to the relatively small diameters, short
heights, and high densities of our nanowire arrays.

21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess