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2012/02/15

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  • Electronics and Optelectronics
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The study of carrier multiplication has become an essential part of many-body physics and materials science. Assistant Prof Hideki Hirori and co-workers observed that when exposed to a single-cycle electric field pulse at the 1000 GHz (terahertz) frequency range, a sample of standard semiconductor material (gallium arsenide, GaAs) burst an avalanche of electron-hole pairs (excitons) 1,000-times more abundant than initial states only on the picosecond (10-12 s) time scale. The observed bright luminescence associated with carrier multiplication suggests that carriers coherently driven by a strong electric field can efficiently gain enough kinetic energy to induce a series of impact ionizations. These just-released results with the world strongest terahertz pulses demonstrate the rich potential that lies in the study of terahertz radiation.
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