Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of a wavelength sized optical vortex knot   In the past decade, optical vortex knots with axial dimensions on the order
of $10^2-10^5$ wavelengths ($\lambda$) have been implemented in the laboratory.
However, many potential applications require a drastic reduction on the the
size of these knots to the order of $\lambda$. In this work, we show the first
measurement of an optical vortex knot (trefoil) with an axial length of $1.99\,
\lambda$ contained within a volume ($x\times y\times z$) of $1.90\times
2.19\times 1.99 \, \lambda^3$. Prior to focusing, the laser light is linearly
polarized ($x$, horizontal) and we observe the knot in the dominant $x$
polarization component of the tightly focused field. We also observe the
transition of the trefoil knot to a couple of vortex loops via reconnection of
the vortex lines as we change the spatial scale of the angular spectrum
representation of the field.

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The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con