Quantum theory of electron tunneling into intersubband cavity polariton states

Through a nonperturbative quantum theory, we investigate how the quasielectron excitations of a two-dimensional electron gas are modified by strong coupling to the vacuum field of a microcavity. We show that the electronic dressed states originate from a Fano-type coupling between the bare electron states and the continuum of intersubband cavity polariton excitations. In particular, we calculate the electron spectral function modified by light-matter interactions and its impact on the electronic injection of intersubband cavity polaritons. The domain of validity of the present theoretical results is critically discussed. We show that resonant electron tunneling from a narrow-band injector can selectively excite super-radiant states and produce efficient intersubband polariton electroluminescence.