Temperature dependent characteristics of λ∼3.8μm room-temperature continuous-wave quantum-cascade lasers

Temperature dependent characteristics of $\lambda \sim 3.8\mu \mathrm{m}$ quantum-cascade lasers (QCLs) operating up to $318\mathrm{K}$ in continuous-wave (cw) mode are reported. A high-reflectivity coated $11.5\text{-}\mu \mathrm{m}$ -wide and $4\text{-}\mathrm{mm}$ -long epilayer-down bonded QCL using a diamond submount shows a considerable improved cw operation with an output power of $143\mathrm{mW}$ and a threshold current density of $1.51\mathrm{kA}∕{\mathrm{cm}}^2$ at $298\mathrm{K}$ . The temperature dependence on optical and electrical performances of the QCLs with respect to the output power, slope efficiency, threshold current/voltage, turn-on voltage, differential series resistance, and emission wavelength are investigated systematically above liquid nitrogen temperature.