Terahertz electromagnetic wave generation from quantum nanostructure

We have investigated terahertz (THz) electromagnetic wave generation from s emiconductor quantum nanostructures. The samples used in our experiment are a GaAs/AlGaAs symmetric triple-coupled quantum well and a GaAs/AlGaAs cres cent-shaped quantum wire. The THz electromagnetic waves were generated by u ltrashort optical pulse excitation and detected by a spatial electrooptic ( EO) sampling method. Generation of a THz electromagnetic wave, which origin ats from quantum beats with three frequency components of 0.8, 1.0, and 1.8 THz, was observed in the symmetric triple-coupled quantum well. In a quant um wire, THz electromagnetic wave generation due to the instantaneous polar ization accompanied by the creation of excitons by ultrashort optical pulse excitation was observed.