Electron Bloch oscillations and electromagnetic transparency of semiconductor superlattices in multi-frequency electric fields

We examine the phenomenon of electromagnetic transparency in semiconductor superlattices having various miniband dispersion laws in the presence of multi-frequency periodic and nonperiodic electric fields. Effects of induced transparency and spontaneous generation of static fields are discussed. We pay special attention to self-induced electromagnetic transparency and its correlation to dynamic electron localization. Processes and mechanisms of the transparency formation, collapse, and stabilization in the presence of external fields are studied. In particular, we present the numerical results of the time evolution of the superlattice current in an external biharmonic field showing main channels of transparency collapse and its partial stabilization in the case of low-electron-density superlattices.