Self-generated Bloch oscillations in biased semiconductor superlattices

We present theoretical simulations of the highly nonlinear ultrafast intraband response of photoexcited biased semiconductor superlattices. Usually, when Bloch oscillating wave packets are created in superlattices, the required coherences arise purely from a spectrally broad external optical pulse that couples different Wannier-Stark ladder states. However, we show that if the pulse intensity is high enough, then even if the optical pulse is spectrally much narrower than the Wannier-Stark ladder spacing, Bloch oscillating wave packets will be generated by the ultrafast nonadiabatic change in the self-generated internal dc electric field that arises from the formation of excitons with permanent dipole moments.