Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A High-Q Vertical Light Emission From Active Parity-Time Symmetric
  Gratings   This work presents a theoretical investigation of an active photonic grating
of the parity-time (PT) symmetric architecture. The analytical study of the
free-space mode propagation from the grating structure indicates the unique
bifurcation property due to the PT-symmetry modulation. It is shown that both
the gain/loss contrast and the lattice constant parameters are critical factors
to modulate the active photonic system in between the PT-symmetry to the
symmetry-broken phases. Furthermore, numerical simulations via the Rigorous
Coupled-Wave Analysis (RCWA) method discover the existence of a unique Spectral
Singularity (SS) phenomenon in this PT grating structure, which corresponds to
a non-trivial single-mode and near-zero bandwidth photonic resonant emission.
Also, the guiding procedure for fulfilling SS modes is found to be related to
the unique formation of the scattering matrix applied in the PT-symmetric
photonic gratings. This theoretical work takes a fresh look into the active
PT-symmetric photonic gratings focusing on the discovery of new free-space
emission modes rather than the commonly studied unidirectional properties,
which could contribute to the development of novel low-threshold and
super-coherent surface-emitting devices.

8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph