Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Materials processing with tightly focused femtosecond vortex laser beams   This letter is the first demonstration of material modification using tightly
focused femtosecond laser vortex beams. Double-charge femtosecond vortices were
synthesized with the polarization-singularity beam converter described in Ref
[1] and then focused using moderate and high numerical aperture optics (viz.,
NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling
the pulse energy we consistently machine high-quality micron-size ring-shaped
structures with less than 100 nm uniform groove thickness.

17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ