Abstract

Their inherently broadband gain and high value of the third order nonlinearity makes quantum cascade lasers (QCLs) ideal candidates for frequency comb generation in the terahertz (THz) and mid-infrared (midIR) spectral ranges. In recent years, it has been demonstrated that free running QCLs can produce broad comb spectra, even without any special endeavour to induce phase-locking of the lasing modes [1]. Unfortunately, such “coherent” regimes of multimode operation seem to span only a very narrow portion of the full dynamic range of the devices, which hinders the practical usability of this technology [1,2].

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