  The non-symmetrized current noise is crucial for the analysis of light
emission in nanojunctions. The latter represent non-classical photon emitters
whose description requires a full quantum approach. It was found experimentally
that light emission can occur with a photon energy exceeding the applied dc
voltage, which intuitively should be forbidden due to the Pauli principle. This
overbias light emission cannot be described by the single-electron physics, but
can be explained by two-electron or even three-electron processes, correlated
by a local resonant mode in analogy to the well-known dynamical Coulomb
blockade (DCB). Here, we obtain the non-symmetrized noise for junctions driven
by an arbitrarily shaped periodic voltage. We find that when the junction is
driven, the overbias light emission exhibits intriguingly different features
compared to the dc case. In addition to kinks at multiples of the bias voltage,
side kinks appear at integer multiples of the ac driving frequency. Our work
generalizes the DCB theory of light emission to driven tunnel junctions and
opens the avenue for engineered quantum light sources, which can be tuned
purely by applied voltages.
