Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Four wave mixing with self-phase matching due to collective atomic
  recoil   We describe a method for non-degenerate four-wave mixing in a cold sample of
  4-level atoms. An integral part of the four-wave mixing process is a
collective instability which spontaneously generates a periodic density
modulation in the cold atomic sample with a period equal to half of the
wavelength of the generated high-frequency optical field. Due to the generation
of this density modulation, phase-matching between the pump and scattered
fields is not a necessary initial condition for this wave-mixing process to
occur, rather the density modulation acts to "self phase-match" the fields
during the course of the wave-mixing process. We describe a one-dimensional
model of this process, and suggest a proof-of-principle experiment which would
involve pumping a sample of cold Cs atoms with three infra-red pump fields to
produce blue light.

12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph