High-power continuous-wave operation of quantum-cascade lasers up to 60/spl deg/C

High-temperature high-power continuous-wave (CW) operation of high-reflectivity-coated 12-/spl mu/m-wide quantum-cascade lasers emitting at /spl lambda/ = 6 /spl mu/m with a thick electroplated Au top contact layer is reported for different cavity lengths. For a 3-mm-long laser, the CW optical output powers of 381 mW at 293 K and 22 mW at maximum operating temperature of 333 K (60/spl deg/C) are achieved with threshold current densities of 1.93 and 3.09 kA/cm/sup 2/, respectively. At 298 K, the same cavity gives a maximum wall plug efficiency of 3.17% at 1.07 A. An even higher CW optical output power of 424 mW at 293 K is obtained for a 4-mm-long laser and the device also operates up to 332 K with an output power of 14 mW. Thermal resistance is also analyzed at threshold as a function of cavity length.