Abstract
We report the first observation of stimulated emission of terahertz radiation from internal transitions of excitons. The far-infrared electromagnetic response of is monitored via broadband terahertz pulses after ultrafast resonant excitation of three-dimensional excitons. Stimulated emission from the to the energetically lower bound level occurs at a photon energy of 6.6 meV, with a cross section of . Simultaneous excitation of both exciton levels, in turn, drives quantum beats, which lead to efficient terahertz emission sharply peaked at the difference frequency.
- Received 12 June 2005
DOI:https://doi.org/10.1103/PhysRevLett.96.017402
©2006 American Physical Society