Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Impedance matching of inverted conductors: Two-dimensional beam
  splitters with divergent gain   A thin conducting sheet - graphene, for example - transmits, absorbs, and
reflects radiation. A sheet that is very thin, even vanishingly so, can still
produce 50% absorption at normal incidence if it has conductivity corresponding
to half the impedance of free space. We find that, regardless of the sheet
conductivity, there exists a combination of polarization and angle of incidence
that achieves this impedance half-matching condition. If the conducting medium
can be inverted, the conductivity is formally negative and the sheet amplifies
the incident radiation. To the extent that a negative half-match in a thin
sheet can be maintained, enormous single-pass gain in both transmission and
reflection is possible. Known semiconductors (e.g., gallium nitride) have the
optical properties necessary to give large amplification in a structure that
is, remarkably, both thin and nonresonant.

15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th