Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Broadband optical gain via interference in the free electron laser:
  principles and proposed realizations   We propose experimentally simplified schemes of an optically dispersive
interface region between two coupled free electron lasers (FELs), aimed at
achieving a much broader gain bandwidth than in a conventional FEL or a
conventional optical klystron composed of two separated FELs. The proposed
schemes can {\it universally} enhance the gain of FELs, regardless of their
design when operated in the short pulsed regime.

17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci