Low Threshold Current Density Operation of Strain-Compensated Quantum Cascade Laser

We report the low threshold current density operation of strain-compensated
In _0.64 Ga _0.36 As/In _0.38 Al _0.62 As quantum cascade lasers emitting near 4.94μm. By employing an enlarged strain-compensated structure and optimizing the injector doping density, a rather low threshold current density of 0.57kA/cm² at 80K is achieved for an uncoated 20-μm-wide and 2.5-mm-long laser.