Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence of Linear Chirp in Mid-Infrared Quantum Cascade Lasers   We measure the inter-modal phase relation of a quantum cascade laser
frequency comb operating at 8 um using a coherent beatnote spectroscopy. We
find these phases to be reproducible after cycling the power of the device, and
to be smoothly varying with driving current. Moreover, these phases describe a
comb state exhibiting a simple, linear chirp, which in fact corresponds to the
lowest state of chirp to minimise the amplitude modulation, as required for
combs driven by four wave mixing in a gain medium with a short gain recovery
lifetime.

25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th