Abstract
Terahertz time-domain spectroscopy is widely used in a broad range of applications where knowledge of both the amplitude and phase of a terahertz wave can reveal useful information about a sample1. However, a means of amplifying terahertz pulses, which would be of great benefit in improving the applicability of time-domain spectroscopy, is lacking. Although terahertz quantum cascade lasers2 are promising devices for terahertz amplification3, gain clamping4 limits the attainable amplification5. Here, we circumvent gain clamping and demonstrate amplification of terahertz pulses by ultrafast gain switching of a quantum cascade laser through the use of an integrated Auston switch6. This unclamps the gain by placing the laser in a non-equilibrium state that allows large amplification of the electromagnetic field within the cavity. This technique offers the potential to produce high field terahertz pulses that approach the quantum cascade laser saturation field.
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Acknowledgements
This work was financially supported by the Direction Générale de l'Armement (DGA), Centre de compétence NanoSciences (CNano), Agence Nationale de la Recherche (ANR), Engineering and Physical Sciences Research Council (EPSRC) and the EC NOTES programme. The Laboratoire Pierre Aigrain, École Normale Supérieure (LPA-ENS) is a ‘Unité Mixte de Recherche Associée au Centre Nationale de la Recherche Scientifique (CNRS) UMR8551 et aux Universités Paris 6 et 7’. Device fabrication was performed at the nanocentre Institut d'Électronique Fondamentale-Minerve (CTU-IEF-Minerve), which was partly funded by the ‘Conseil General de l'Essonne’.
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Data were taken by N.J., S.S.D., D.O. and J.M., and analysed by N.J. and S.S.D. The experiment was conceived by N.J. Samples were grown by S.P.K., E.H.L. and A.G.D., and processed by C.M., S.B. and C.S. The manuscript was prepared by N.J., S.S.D. and J.T. with contributions from S.B., C.S. and E.H.L. J.T. and S.S.D. supervised and coordinated all work.
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Jukam, N., Dhillon, S., Oustinov, D. et al. Terahertz amplifier based on gain switching in a quantum cascade laser. Nature Photon 3, 715–719 (2009). https://doi.org/10.1038/nphoton.2009.213
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DOI: https://doi.org/10.1038/nphoton.2009.213
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