  Control over the spontaneous emission of light through tailored optical
environments remains a fundamental paradigm in nanophotonics. The use of
highly-confined plasmons in materials such as graphene provides a promising
platform to enhance transition rates in the IR-THz by many orders of magnitude.
However, such enhancements involve near-field plasmon modes or other kinds of
near-field coupling like quenching, and it is challenging to use these highly
confined modes to harness light in the far-field due to the difficulty of
plasmonic outcoupling. Here, we propose that through the use of radiative
cascade chains in multi-level emitters, IR plasmons can be used to enhance far
field spectra in the visible and UV range, even at energies greater than 10 eV.
Combining Purcell-enhancement engineering, graphene plasmonics, and radiative
cascade can result in a new type of UV emitter whose properties can be tuned by
electrically doping graphene. Varying the distance between the emitter and the
graphene surface can change the strength of the far-field emission lines by two
orders of magnitude. We also find that the dependence of the far-field emission
on the Fermi energy is potentially extremely sharp at the onset of interband
transitions, allowing the Fermi energy to effectively serve as a "switch" for
turning on and off certain plasmonic and far-field emissions.
