InGaAs/AlInAs quantum cascade laser sources based on intra-cavity second harmonic generation emitting in 2.6-3.6 micron range

We discuss the design and performance of quantum cascade laser sources based on intra-cavity second harmonic generation operating in at wavelengths shorter than 3.7μm. A passive heterostructure tailored for giant optical nonlinearity is integrated on top of an active region and patterned for quasi-phasematching. We demonstrate operation of λ≈3.6μm, λ≈3.0μm, and λ≈2.6μm devices based on lattice-matched and strain-compensated InGaAs/AlInAs/InP materials. Threshold current densities of typical devices with nonlinear sections are only 10-20% higher than that of the reference lasers without the nonlinear section. Our best devices have threshold current density of 2.2kA/cm and provide approximately 35μW of second-harmonic output at 2.95μm at room temperature. The second-harmonic conversion efficiency is approximately 100μW/W. Up to two orders of magnitude higher conversion efficiencies are expected in fully-optimized devices.