Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Experimental demonstration of Cavity-Free Optical Isolators and Optical
  Circulators   Cavity-free optical nonreciprocity components, which have an inherent strong
asymmetric interaction between the forward- and backward-propagation direction
of the probe field, are key to produce such as optical isolators and
circulators. According to the proposal presented by Xia et al., [Phys. Rev.
Lett. 121, 203602 (2018)], we experimentally build a device that uses
cross-Kerr nonlinearity to achieve a cavity-free optical isolator and
circulator. Its nonreciprocal behavior arises from the thermal motion of N-type
configuration atoms, which induces a strong chiral cross-Kerr nonlinear
response for the weak probe beam. We obtain a two-port optical isolator for up
to 20 dB of isolation ratio in a specially designed Sagnac interferometer. The
distinct propagation directions of the weak probe field determine its
cross-phase shift and transmission, by which we demonstrate the accessibility
of a four-port optical circulator.

37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat