  We study quasi-particle transmission through an $n $-$p$ junction in a
graphene irradiated by an electromagnetic field (EF). In the absence of EF the
electronic spectrum of undoped graphene is gapless, and one may expect the
perfect transmission of quasi-particles flowing perpendicular to the junction.
We demonstrate that the resonant interaction of propagating quasi-particles
with the component of EF parallel to the junction induces a
\textit{non-equilibrium dynamic gap} $(2\Delta_R)$ between electron and hole
bands in the quasi-particle spectrum of graphene. In this case the strongly
suppressed quasi-particle transmission is only possible due to interband
tunnelling. The effect may be used for controlling transport properties of
diverse structures in graphene, like, e.g., $n$-$p$-$n$ transistors, single
electron transistors, quantum dots, etc., by variation of the intensity $S$ and
frequency $\omega$ of the external radiation.
