Thermal characteristics of InP-based mid-infrared quantum cascade lasers at λ∼ 8.8 Aμm

We have theoretically investigated the thermal characteristics of double-channel ridge-waveguide InGaAs/AlInAs quantum cascade lasers (QCLs) emitting at lambda similar to 8.8 A mu m in comparison with the experimental results. Based on the measured data, the thermal parameters were obtained with heat source densities using a two-dimensional anisotropic heat dissipation model. For 21 A mu m x 4 mm QCLs, the thermal conductance (G (th) ) value was 215.5W/K-cm(2) at 298 K in continuous-wave (CW) operation. The G (th) value was significantly increased by using a buried heterostructure (BH) via the regrowth of undoped InP layer around the laser ridge. Also, an additional improvement in the G (th) was made by the use of a diamond submount, and the temperature dependency of the devices was largely decreased. The G (th) value was improved to 306.7 W/K-cm(2) at 298 K in the CW mode for epilayer-down bonded BH QCLs with an InP embedded layer on a diamond submount.