Bloch oscillations at room temperature

We report on the observation of coherent electronic wave-packet oscillations in a semiconductor heterostructure at room temperature. Bloch oscillations are excited in a wide-miniband GaAs/${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As superlattice by femtosecond laser pulses. Several cycles of the coherent electronic motion are observed within the dephasing time of the intraband polarization. The frequency can be tuned by the applied electric field from 4.5 to 8 THz.