Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Freestanding metasurfaces for optical frequencies   We present freestanding metasurfaces operating at optical frequencies with a
total thickness of only 40$\,$nm. The metasurfaces are fabricated by focused
ion beam milling of nanovoids in a carbon film followed by thermal evaporation
of gold and plasma ashing of the carbon film. As a first example, we
demonstrate a metasurface lens based on resonant V-shaped nanovoids with a
focal length of 1$\,$mm. The second example is a metasurface phase-plate
consisting of appropriately oriented rectangular nanovoids that transforms a
Gaussian input beam into a Laguerre-Gaussian ${LG_{-1,0}}$ mode.

15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph