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Mode-locked semiconductor terahertz laser

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Ultrashort pulses of terahertz frequency radiation can now be generated by semiconductor lasers. This is what a team of physicists has demonstrated using quantum cascade lasers, an electrically pumped semiconductor light source based on multi-quantum wells.
By modulating the injected current of a terahertz quantum cascade laser the researchers have shown that it is possible to add up coherently the Fabry-Perot modes oscillating in the laser cavity, a technique known as active mode-locking.
The result is a train of 10-picosecond-long regular pulses, that have been measured by sampling the terahertz wave with a femtosecond fiber-laser (see the Figure). This is the first time that ultrashort terahertz pulses are generated directly by a semiconductor laser.
These results are the fruit of a Franco-British collaboration and have been published online the 24th of April in Nature Photonics. The research team was coordinated by the Laboratoire MPQ of the University of Paris-Diderot and CNRS, in partnership with the Laboratoire LNE-SYRTE of the Observatoire de Paris, and the School of Electronic and Electrical Engineering, University of Leeds, UK.

Figure :

Picosecond pulses of a terahertz laser

Contact :

Stefano Barbieri.

Référence :

Coherent sampling of active mode-locked terahertz quantum
cascade lasers and frequency synthesis.

S. Barbieri, M. Ravaro, P. Gellie, G. Santarelli, C. Manquest, C. Sirtori, S. P. Khanna, E. H. Linfield, and A. G. Davies , Nature Photonics 5, 306 (2011)