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Thermal analysis and heat dissipation improvement for quantum cascade lasers through experiments, simulations, and structure function

We quantified the thermal resistance of quantum cascade lasers (QCLs) using their structure functions and increased the laser output by employing ridge structures in which thermal resistance was reduced. To improve heat properties, three different QCL devices were prepared as follows. One was a device whose ridge was covered with SiO2, another was a device whose ridge was embedded with Au, and the other was a device whose ridge was embedded with Cu. The temperature distributions were measured with a thermoviewer and were analyzed with three-dimensional simulations. From the results, improved heat dissipation by embedding the ridge was clarified. Furthermore, the structure functions obtained by static mode measurement suggested that the thermal resistance was improved from 9.3 to 6.5 K W−1 by embedding the ridge. As a result of the improvement, the QCL with the Au-embedded ridge had a 1.5-fold higher laser power than the QCL with the SiO2-covered ridge.