Terahertz emission from black silicon

We report on a terahertz emitter made out of black silicon. The black surface structure absorbs the whole optical pump power in the very surface. In contrast to expectations for indirect semiconductors, the black structure shows an emission in the terahertz range. The emitted radiation of the black silicon crystal is characterized for different parameters using terahertz time-domain spectroscopy. (c) 2008 American Institute of Physics.