Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nodal Areas and Structured Darkness   Generalized beams of light that are made to turn inside out, creating black
nodal areas of total destructive interference are described. As an example we
experimentally created an elliptical node from a uniformly illuminated
elliptical aperture by use of a lossless phase mask called a q-plate. We
demonstrate how a modified phase retrieval algorithm may be used to design
phase masks that achieve this transformation for an arbitrary aperture shape
when analytical methods are not available. This generic wave phenomenon may
find uses in both optical and non-optical systems.

29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci