Experimental realization of the Bloch oscillator in a semiconductor superlattice.

We detect the coherent submillimetre-wave radiation from electron Bloch oscillations in a biased GaAs/AlGaAs semiconductor superlattice by time-resolved terahertz (THz) spectroscopy. The emitted THz radiation is tunable from 0.3 to 4 THz. The emission from Bloch oscillations is observable for temperatures as high as 100 K.