21 February 2011 Ultrafast gain switching of THz quantum cascade lasers
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Terahertz (THz) time domain spectroscopy (TDS) is widely used in a broad range of applications where knowledge of both the amplitude and phase of a THz wave can reveal useful information about a sample. However, a means of amplifying THz pulses which would be of great benefit for improving the applicability of TDS is lacking. While THz quantum cascade lasers (QCL) are promising devices for THz amplification, gain clamping limits the attainable amplification. Here we circumvent gain clamping and demonstrate amplification of THz pulses by ultrafast gain switching of a QCL via the use of an integrated Auston switch. 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 THz pulses that approach the QCL saturation field.
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S. S. Dhillon, S. S. Dhillon, N. Jukam, N. Jukam, D. Oustinov, D. Oustinov, R. Rungsawang, R. Rungsawang, J. Madéo, J. Madéo, S. Barbieri, S. Barbieri, C. Manquest, C. Manquest, C. Sirtori, C. Sirtori, S. P. Khanna, S. P. Khanna, E. H. Linfield, E. H. Linfield, A. G. Davies, A. G. Davies, J. Tignon, J. Tignon, "Ultrafast gain switching of THz quantum cascade lasers", Proc. SPIE 7937, Ultrafast Phenomena in Semiconductors and Nanostructure Materials XV, 79370P (21 February 2011); doi: 10.1117/12.870833; https://doi.org/10.1117/12.870833

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