The description of heat dissipation stages in quantum cascade lasers: experiment and analytics

Efficient heat extraction from the active region of a quantum cascade laser (QCL) constitutes a critical requirement for achieving stable continuous-wave operation and ensuring long-term device reliability. A central challenge in this context lies in the effectiveness of post-growth processing steps applied to the heterostructure, as well as in the subsequent assembly of the QCL chip. In this work, a theoretical model describing heat propagation within a QCL chip is developed, revealing the inherently nonuniform nature of the thermal transport process. This behavior is characterized by an effective thermal diffusivity parameter, which serves as a quantitative measure of heat removal efficiency from the active region. It is further demonstrated that this parameter can be experimentally extracted through analysis of the nonlinear frequency chirp of Fabry–Perot modes.