High-power, room-temperature, and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ∼4.8μm

A high-power continuous-wave (CW) operation of distributed-feedback quantum-cascade lasers using a buried grating with epitaxial regrowth up to temperatures of above $60°\mathrm{C}$ is demonstrated. For a high-reflectivity-coated $13\mu \mathrm{m}$ -wide and $3\mathrm{mm}$ -long cavity, CW output powers of $135\mathrm{mW}$ at $25°\mathrm{C}$ and still $37\mathrm{mW}$ at $60°\mathrm{C}$ are obtained. The device exhibits a CW threshold current density of $1.1\mathrm{kA}∕{\mathrm{cm}}^2$ , a maximum CW wall-plug efficiency of 1.48% at $25°\mathrm{C}$ , and a characteristic temperature of $177\mathrm{K}$ in pulsed mode. Single-mode emission near $4.8\mu \mathrm{m}$ with a side-mode suppression ratio of $>30\mathrm{dB}$ and a tuning range of $\sim 8.1{\mathrm{cm}}^{-1}$ (i.e., tunability of $0.18{\mathrm{cm}}^{-1}∕\mathrm{K}$ ) in the temperature range from $15\text{to}60°\mathrm{C}$ is observed.