Terahertz Electromagnetic Wave Generation from Quantum Nanostructure

We have investigated terahertz (THz) electromagnetic wave generation from semiconductor quantum nanostructures.The samples used in our experiment are a GaAs/AlGaAs symmetric triple-coupled quantum well and a GaAs/AlGaAs crescent-shaped quantum wire. The THz electromagnetic waves were generated by ultrashort optical pulse excitation and detected by a spatial electrooptic (EO) sampling method. Generation of a THz electromagnetic wave, which originats 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 quantum wire, THz electromagnetic wave generation due to the instantaneous polarization accompanied by the creation of excitons by ultrashort optical pulse excitation was observed.