Nonequilibrium approach for intersubband optics

In this review I summarize current challenges for intersubband laser development devices from a microscopic point of view, as well as recent theoretical results, which indicate the relevance of nonequilibrium many body effects in the complex scattering and correlation microscopic mechanisms underlying the operation of those devices. The strongly nonthermal nature of the electronic wave functions, the fact that the energy difference between the subbands relevant for laser action are of the order of many body effects, and of the resulting level broadening, the Coulomb enhanced cross absorption, as well as the need to account for dephasing in the transport, require our advanced nonequilibrium many body approach for predictive simulations. I further demonstrate that the coupling between light and intersubband excitations in semiconductors is fundamentally different from the well understood coupling to interband transitions leading to excitonic polaritons. Dispersion relations of a more appropriate intersubband antipolariton quasiparticle concept are presented.