Room-Temperature λ ≈ 2.7 μm 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 mu m emission wavelength with a record high peak conversion efficiency of 278mW/W-2 at 80 K and still around 10 mu W at 2.73 mu m emission wavelength with 770 mu W/W-2 conversion efficiency at room temperature. Experimental threshold current densities are demonstrated to be as low as 1.5 kA/cm(2) at room temperature.