High-temperature continuous-wave operation of ?~8 m quantum cascade lasers

We report single-mode continuous-wave operation of a λ∼8 μm quantum cascade laser at 140 K. The threshold current density is 4.2 kA/cm2 at 300 K in pulsed mode and 2.5 kA/cm2 at 140 K in continuous wave for 2 mm long index-guided laser cavities of 20 μm width. Wide stripe (W∼100 μm), index-guided lasers from the same wafer in pulsed operation demonstrate an average T0 of 210 K with other wafers demonstrating a T0 as high as 290 K for temperatures from 80 to 300 K. This improvement in high-temperature performance is a direct result of three factors: excellent material quality, a low-loss waveguide design, and a low-leakage index-guided laser geometry.