Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Carbon dioxide absorption spectroscopy with a mid-infrared silicon
  photonic waveguide   Carbon dioxide is a vital gas for life on Earth, a waste product of human
activities, and widely used in agriculture and industry. Its accurate sensing
is therefore of great interest. Optical sensors exploiting the mid-infrared
light absorption of CO$_{\mathrm{2}}$ provide high selectivity, but their large
size and high cost limit their use. Here, we demonstrate CO$_{\mathrm{2}}$ gas
sensing at 4.2 $\mu$m wavelength using an integrated silicon waveguide,
featuring a sensitivity to CO$_{\mathrm{2}}$ of 44 % that of free-space
sensing. The suspended waveguide is fabricated on a silicon-on-insulator
substrate by a single-lithography-step process, and we route it into a
mid-infrared photonic circuit for on-chip-referenced gas measurements. Its
demonstrated performance and its simple and scalable fabrication make our
waveguide ideal for integration in miniaturized CO$_{\mathrm{2}}$ sensors for
distributed environmental monitoring, personal safety, medical, and high-volume
consumer applications.

26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con