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.
Huber
Rupert
R
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
Schmid
Ben A
BA
Shen
Y Ron
YR
Chemla
Daniel S
DS
Kaindl
Robert A
RA