Terahertz sources based on intracavity frequency mixing in mid-infrared quantum cascade lasers with passive nonlinear sections

We report the design and performance of terahertz quantum cascade laser sources based on intracavity difference frequency generation in dual-wavelength mid-infrared quantum cascade lasers with a passive nonlinear section at the exit facet, designed for giant second-order nonlinear susceptibility. These devices operate in the mid-infrared at $λ1=8.4μm$ and $λ2=9.5μm$⁠, with terahertz output at the difference frequency, $λ3≈73μm$⁠. Terahertz output of approximately 100 nW was observed up to a heat sink temperature of 210 K.