Very high average power at room temperature from λ≈5.9-μm quantum-cascade lasers

We report a very high average output power at room temperature for quantum-cascade lasers emitting at λ≈5.9 μm. For high-reflectivity-coated 2-mm-long cavities, a low threshold current density of 1.7 kA/cm2 was obtained at room temperature. From 300 to 400 K, the characteristic temperature (T0) was 198 K. A maximum average output power of 0.67 W was achieved. In addition, 0.56 W average output power was observed at a duty cycle of 56%.