We present a microscopic analysis of coherent effects induced by elect
ric fields in photoexcited semiconductors in the presence of the Coulo
mb interaction. Both the terahertz emission and four-wave-mixing signa
ls arising from Bloch oscillations in a semiconductor superlattice are
computed consistently. It is predicted that Bloch oscillations should
be observable also for miniband widths on the order of the exciton bi
nding energy.