In this paper, we report the results of investigation of 9.5 µm AlGaAs/GaAs and strain compensated 4.7 µm AlInAs/InGaAs/InP QCLs. We also show the results for 9.5 µm lasers based on lattice matched AlInAs/InGaAs/InP structures. The developed GaAs/AlGaAs lasers show the record pulse powers of 6 W at 77 K and up to 50 mW at 300 K. This has been achieved by careful optimization of the MBE growth process and by applying a high reflectivity metallic coating to the back facet of the laser. The 9.5 µm AlInAs/InGaAs/InP lasers utilize AlInAs waveguide and were grown exclusively by MBE without MOCVD regrowth. The short wavelength, strain compensated QCLs were grown by MOCVD. They represent state‐of‐the‐art parameters for the devices of their design. For epitaxial process control, the atomic‐force microscopy (AFM), high resolution X‐ray diffraction (HR‐XRD) and transmission electron microscopy (TEM) were used to characterize the morphological and structural properties of the layers. The basic electro‐optical characterization of the lasers is provided. We also present results of Green's function modeling of mid‐IR QCLs and demonstrate the capability of non‐equilibrium Green's function (NEGF) approach for sophisticated but still computationally effective simulation of laser's characteristics.

We report on detailed experimental investigation of thermal properties of AlGaAs/GaAs quantum cascade lasers (QCLs) emitting at wavelength of 9.4 μm. Different mounting options and device geometries are compared in terms of their influence on the relative increase of the active region temperature. High resolution, spatially resolved thermoreflectance is used for mapping temperature distribution over the facet of pulse operated QCLs. The devices’ thermal resistances are derived from experimental data. We also develop a numerical thermal model of QC lasers, solving heat transport equation in 2D and 3D, which includes anisotropy of thermal conductivity. By combining experimental and numerical results, an insight into thermal management in QCLs is gained. Thermal optimization of the design focuses on improving heat dissipation in the device, which is essential to increase the maximal operation temperature of the devices.

A methodological approach for advanced facet temperature characterization of operating diode lasers is presented. It relies on the concerted application of micro-Raman spectroscopy and thermoreflectance mapping. The latter technique allows for fast facet mapping, whereas the Raman data provide the temperature calibration. Residual effects, e.g., caused by the different reflectances of the materials involved into the laser structure, are discussed. Since both techniques provide rather complementary information, their concerted application appears as an effective tool for advanced device inspection.

The development of charge coupled device thermoreflectance (CCD TR) instrumentation for accurate and rapid evaluation of the thermal characteristics of quantum cascade lasers is demonstrated. The thermal characterization of such devices provides a mode for comparing different operating conditions, geometries and device designs. The method allows for registration of the high-resolution maps of the temperature distribution in a time not exceeding several seconds. The capabilities of the CCD TR are compared with standard TR spectroscopy.

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