Bloch oscillation under a bichromatic laser: Dynamical delocalization and localization, persistent terahertz emission, and harmonics generation

National Laboratory for Superlattices and Microstructures Institute of Semiconductors, Chinese Academy of Sciences P. O. Box 912, Beijing 100 083, PRC and Centre for Advanced Study, Tsinghua University - Beijing 100 084, PRC

Received: 24 November 1999
Accepted: 13 March 2000

Abstract

A novel AC driving configuration is proposed for biased semiconductor superlattices, in which the THz driving is provided by an intense bichromatic cw laser in the visible light range. The frequency difference between two components of the laser is resonant with the Bloch oscillation. Thus, multi-photon processes mediated by the conduction (valence) band states lead to dynamical delocalization and localization of the valence (conduction) electrons, and to the formation and collapse of quasi-minibands. Thus, driven Bloch oscillators are predicted to generate persistent THz emission and harmonics of the dipole field, which are tolerant of the exciton and the relaxation effects.