Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The combination of directional outputs and single-mode operation in
  circular microdisk with broken PT symmetry   Monochromaticity and directionality are two key characteristics of lasers.
However, the combination of directional emission and single-mode operation is
quite challenging, especially for the on-chip devices. Here we propose a
microdisk laser with single-mode operation and directional emissions by
exploiting the recent developments associated with parity-time (PT) symmetry.
This is accomplished by introducing one-dimensional periodic gain and loss into
a circular microdisk, which induces a coupling between whispering gallery modes
with different radial numbers. The lowest threshold mode is selected at the
positions with least initial wavelength difference. And the directional
emissions are formed by the introduction of additional grating vectors by the
periodic distribution of gain and loss regions. We believe this research will
impact the practical applications of on-chip microdisk lasers.

4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
16
The categories of this paper are: stat
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The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin