Room-Temperature $\lambda \approx 2.7~\mu{\rm m}$ Quantum Cascade Laser Sources Based on Intracavity Second-Harmonic Generation

We present experimental results on a short-wavelength quantum cascade laser based on intracavity second-harmonic generation. Our devices consist of an injectorless quantum cascade laser, which serves as a pump, and a transversely integrated passive two-well nonlinear section. The presented devices demonstrate above 1 mW output power at 2.65 μm emission wavelength with a record high peak conversion efficiency of 278 mW/W² at 80 K and still around 10 μW at 2.73 μm emission wavelength with 770 μW/W² conversion efficiency at room temperature. Experimental threshold current densities are demonstrated to be as low as 1.5 kA/cm² at room temperature.