Abstract

Impulsively excited Bloch oscillations in semiconductor superlattices are attractive for th generation of coherent terahertz (THz) electromagnetic radiation tunable with a dc bias field over the wide frequency range from 0.2 to 10 THz. So far, only the emission characteristics at low density of the photo-excited charge carriers (1-3x 10⁹ cm⁻² per well) have been investigated. For enhanced emission efficiency, the carrier density must be increased according to the standard theory of emission from coherent ensembles (superradiany emission), the radiation power should scale quadratically with excitation density. For the signal decay rate, one expects a linear density dependence, with a decay on the 100-fs time scale at about 1x10¹⁰ cm⁻², in analogy to four-wave-mixing (FWM) experiments on single quantum wells.

© 1996 Optical Society of America