Stimulated terahertz emission from intraexcitonic transitions in Cu2O.
We report the first observation of stimulated emission of terahertz radiation from internal transitions of excitons. The far-infrared electromagnetic response of Cu2O is monitored via broadband terahertz pulses after ultrafast resonant excitation of three-dimensional 3p excitons. Stimulated emission from the 3p to the energetically lower 2s bound level occurs at a photon energy of 6.6 meV, with a cross section of approximately 10(-14) cm2. Simultaneous excitation of both exciton levels, in turn, drives quantum beats, which lead to efficient terahertz emission sharply peaked at the difference frequency.
Department of Physics, University of California at Berkeley, and Materials Sciences Division, E.O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. rhuber@lbl.gov
Rupert
R
Huber
Ben A
BA
Schmid
Y Ron
YR
Shen
Daniel S
DS
Chemla
Robert A
RA
Kaindl