Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Subdiffraction and spatial filtering due to periodic spatial modulation
  of the gain/loss profile   We investigate light propagation through materials with periodically
modulated gain/loss profile in both transverse and longitudinal directions,
i.e. in material with two-dimensional modulation in space. We predict effects
of self-collimation (diffraction-free propagation) of the beams, as well as
superdiffusion (spatial frequency filtering) of the beams in depending on the
geometry of the gain/loss lattice, and justify the predictions by numerical
simulations of the paraxial wave propagation equations.

36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio