Widely tuned room temperature terahertz quantum cascade laser sources based on difference-frequency generation

We demonstrate room temperature THz quantum cascade laser sources with a broad spectral coverage based on intracavity difference-frequency generation. Two mid-infrared active cores based on the single-phonon resonance scheme are designed with a THz nonlinearity specially optimized at the high operating fields that correspond to the highest mid-infrared output powers. A Cerenkov phase-matching scheme along with integrated dual-period distributed feedback gratings are used for efficient THz extraction and spectral purification. Single mode emissions from 1.0 to 4.6 THz with a side-mode suppression ratio and output power up to 40 dB and 32 mu W are obtained, respectively. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773189]