Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical Imaging with Undetected Light   We obtained the phase and intensity images of an object by detecting
classical light which never interacted with it. With a double passage of a pump
and a signal laser beams through a nonlinear crystal, we observe interference
between the two idler beams produced by stimulated parametric down conversion.
The object is placed in the amplified signal beam after its first passage
through the crystal, and the image is observed in the interference of the
generated idler beams. High contrast images can be obtained even for objects
with small transmittance coefficient due to the geometry of the interferometer
and to the stimulated parametric emission. Like its quantum counterpart, this
three-colour imaging concept can be useful when the object must be probed with
light at a wavelength for which detectors are not available.

23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg