Coherent THz plasmons in GaAs/AlGaAs superlattices

We report on THz emission from coherent plasma oscillations in GaAs/AlGaAs superlattices after excitation by femtosecond laser pulses. The carriers wh ich oscillate inside the superlattice are either dopant electrons or electr ons that are optically generated by the laser pulses. The oscillations are observable from low temperatures up to room temperature. A nearly full or a full miniband prevents these oscillations as it is the case when the minib and is thermally saturated. (C) 1999 Elsevier Science B.V. All rights reser ved.