High-power continuous-wave operation of a 6 μm quantum-cascade laser at room temperature

We report continuous-wave (cw) operation of quantum-cascade lasers $\text{(λ=6\hspace{0.17em}μ}\mathrm{m})$ using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 308 K $\text{(35\hspace{0.05em}°}\mathrm{C}\mathrm{).}$ The high cw optical output powers of 132 mW at 293 K and 21 mW at 308 K are achieved with threshold current densities of 2.29 and $\text{2.91\hspace{0.17em}}{\mathrm{kA/cm}}^2,$ respectively, for a high-reflectivity-coated 15 μm wide and 2 mm long laser.