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Thermal modeling of quantum cascade lasers with 3D anisotropic heat transfer analysis

Although Quantum cascade lasers (QCLs) are frequently used in sensing, spectroscopy, and free space communication applications, their poor thermal properties lead to high temperature gradients in the devices. To diagnose failure mechanisms of mid-wave infrared (MWIR) QCLs, it is critical to understand their thermal generation and transport characteristics. In this work, we use 3D anisotropic steady state heat transfer analysis to investigate the thermal behavior in lattice matched InP/InAlAs/InGaAs buried heterostructure (Bh) mounted epi-layer side down QCLs. We introduce anisotropic thermal conductivities in the in-plane and cross-plane directions in QCL’s superlattice active region, and study the temperature distribution inside the laser. We consider several configurations, including the overhanging of the laser chip on the submount by different amounts, the choice of front facet dielectric coating materials and their thicknesses, and the width of the active region. Combining these effects, we optimize QCL’s thermal performance. This work aims to provide guidelines for the design of durable QCLs as well as to help diagnose QCL failure mechanisms.