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 $\text{λ≈5.9\hspace{0.17em}μ}\mathrm{m}.$ For high-reflectivity-coated 2-mm-long cavities, a low threshold current density of $\text{1.7\hspace{0.17em}}{\mathrm{kA/cm}}^2$ was obtained at room temperature. From 300 to 400 K, the characteristic temperature ${\mathrm{(T}}_0)$ 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%.