Quantum-cascade lasers operating in continuous-wave mode above 90°C at λ∼5.25μm

We report on the design and fabrication of $\lambda \sim 5.25\mu \mathrm{m}$ quantum-cascade lasers (QCLs) for very high temperature continuous-wave (cw) operation. Cw operation is reported up to a maximum temperature of $90°\mathrm{C}$ $\left(363\mathrm{K}\right)$ . Cw output power is reported in excess of $500\mathrm{mW}$ near room temperature with a low threshold current density of $1.4\mathrm{kA}∕{\mathrm{cm}}^2$ at $298\mathrm{K}$ . Room temperature average power of over $540\mathrm{mW}$ is reported at 50% duty cycle. A high thermal conductance $\left(G_{\mathrm{th}}\right)$ of $340\mathrm{W}∕\mathrm{K}{\mathrm{cm}}^2$ is reported for cw QCLs. A finite element thermal model is used to investigate the $G_{\mathrm{th}}$ and maximum cw operating temperature of the QCLs.