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We report high-power continuous-wave (cw) operation of λ∼9.5 μm quantum-cascade lasers to a temperature of 318 K. A high-reflectivity-coated 19-μm-wide and 3-mm-long device exhibits cw output powers as high as 150 mW at 288 K and still 22 mW at 318 K. In cw operation at 298 K, a threshold current density of 1.57 kA/cm2, a slope efficiency of 391 mW/A, and a maximum wall-plug efficiency of 0.71% are obtained. In pulsed operation, a maximum average power of 317 mW is achieved at 49% duty cycle. The emission wavelength in cw mode is shifted from 9.524 μm at 288 K to 9.547 μm at 313 K near 1.05 A drive current with a temperature tuning coefficient of 0.92 nm/K. [ABSTRACT FROM AUTHOR]

We report on the design and fabrication of λ∼5.25 μm quantum-cascade lasers (QCLs) for very high temperature continuous-wave (cw) operation. Cw operation is reported up to a maximum temperature of 90 °C (363 K). Cw output power is reported in excess of 500 mW near room temperature with a low threshold current density of 1.4 kA/cm2 at 298 K. Room temperature average power of over 540 mW is reported at 50% duty cycle. A high thermal conductance (Gth) of 340 W/K cm2 is reported for cw QCLs. A finite element thermal model is used to investigate the Gth and maximum cw operating temperature of the QCLs. [ABSTRACT FROM AUTHOR]