Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Precise and diffraction-limited waveguide-to-free-space focusing
  gratings   We present the design and characterization of waveguide grating devices that
couple visible-wavelength light at $\lambda=674$ nm from single-mode, high
index-contrast dielectric waveguides to free-space beams forming micron-scale
diffraction-limited spots a designed distance and angle from the grating. With
a view to application in spatially-selective optical addressing, and in
contrast to previous work on similar devices, deviations from the main Gaussian
lobe up to $25$ microns from the focus and down to the $5\times10^{-6}$ level
in relative intensity are characterized as well; we show that along one
dimension the intensity of these weak sidelobes approaches the limit imposed by
diffraction from the finite field extent in the grating region. Additionally,
we characterize the polarization purity in the focal region, observing at the
center of the focus a low impurity $< 3 \times 10^{-4}$ in relative intensity.
Our approach allows quick, intuitive design of devices with such performance,
which may be applied in trapped-ion quantum information processing and
generally in any systems requiring optical routing to or from objects 10s--100s
of microns from a chip surface, but benefitting from the parallelism and
density of planar-fabricated dielectric integrated optics.

27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga