THz emission of coherent plasmons in semiconductor superlattices

Summary form only given. Ultrafast excitation of n-doped GaAs layers leads to THz emission from coherent plasma oscillations. The emission frequency of this THz source is given by the simple plasma frequency formula /spl omega//sub p/=(ne/sup 2//m*/spl epsiv/)/sup 1/2/ where n is the number of extrinsic electrons which are confined between the surface depletion field and the GaAs substrate. The desired frequency can be controlled by changing the number of electrons n via the doping concentration of the material. Another possibility to determine the emission frequency /spl omega//sub p/ is to change the effective mass m* of the electrons. This can be accomplished by placing the electrons in the periodic potential of a superlattice. We study the GaAs/AlGaAs heterostructures which are three superlattices.