Terahertz dynamics of Bloch oscillations in semiconductor superlattices

We have systematically investigated the time-evolution of transient electron transport in semiconductor superlattices (SLs) under dc electric fields for various initial electron distributions created by femtosecond laser pulses. It is found that the terahertz (THz) waveforms are very insensitive to the pump photon energy and that the transient current starts from its maximum as damped cosomega_Bt. We will show that the unique electron distribution under WS localization of electron wave functions in the translational symmetry is essential for the observed phase of the photoinduced current. Furthermore, as a first step toward realization of Bloch oscillators, a preliminary result on the effects of planar photonic crystal electrode on the THz emission will be briefly presented.