Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Terahertz frequency combs exploiting an on-chip solution processed
  graphene-quantum cascade laser coupled-cavity architecture   The ability to engineer quantum-cascade-lasers (QCLs) with ultrabroad gain
spectra and with a full compensation of the group velocity dispersion, at
Terahertz (THz) frequencies, is a fundamental need for devising monolithic and
miniaturized optical frequency-comb-synthesizers (FCS) in the far-infrared. In
a THz QCL four-wave mixing, driven by the intrinsic third-order susceptibility
of the intersubband gain medium, self-lock the optical modes in phase, allowing
stable comb operation, albeit over a restricted dynamic range (~ 20% of the
laser operational range). Here, we engineer miniaturized THz FCSs comprising a
heterogeneous THz QCL integrated with a tightly-coupled on-chip
solution-processed graphene saturable-absorber reflector that preserves
phase-coherence between lasing modes even when four-wave mixing no longer
provides dispersion compensation. This enables a high-power (8 mW) FCS with
over 90 optical modes to be demonstrated, over more than 55% of the laser
operational range. Furthermore, stable injection-locking is showed, paving the
way to impact a number of key applications, including high-precision tuneable
broadband-spectroscopy and quantum-metrology.

11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph