Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Slow-light enhanced gain in active photonic crystal waveguides   Slow light is a fascinating physical effect, raising fundamental questions
related to our understanding of light-matter interactions as well as offering
new possibilities for photonic devices. From the first demonstrations of slow
light propagation in ultra-cold atomic gasses, solid-state Ruby and photonic
crystal structures, focus has shifted to applications, with slow light offering
the ability to enhance and control light-matter interactions. The demonstration
of tuneable delay lines, enhanced nonlinearities and spontaneous emission,
enlarged spectral sensitivity and increased phase shifts illustrate the
possibilities enabled by slow light propagation, with microwave photonics
emerging as one of the promising applications. Here, we demonstrate that slow
light can be used to control and increase the gain coefficient of an active
semiconductor waveguide. The effect was theoretically predicted but not yet
experimentally demonstrated. These results show a route towards realizing
ultra-compact optical amplifiers for linear and nonlinear applications in
integrated photonics and prompts further research into the rich physics of such
structures.

10
The categories of this paper are: q-bio
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat