Temperature dependence of a mid-infrared quantum cascade laser with external optical feedback

Quantum cascade lasers (QCLs) exploit radiative intersubband transitions within the conduction band of semiconductor heterostructures. The wide range of wavelengths achievable with QCLs, from mid-infrared to terahertz range, leads to a large number of applications including absorption spectroscopy, optical countermeasures and free space communications requiring stable single-mode operation with a narrow linewidth, high output power and high modulation bandwidth. Prior work has unveiled the occurrence of temporal chaos in a QCL subjected to optical feedback, with a scenario involving oscillations at the external cavity frequency and low-frequency fluctuations. The purpose of this work is to further investigate the temperature dependence of a mid-infrared QCL with optical feedback. When the semiconductor device is cooled down to 170K, experiments unveil that the laser destabilization appears at a lower feedback ratio and that the chaotic bubble slightly expands owing to a different carrier lifetime dynamics. These results are of paramount importance for new mid-infrared applications such as chaos-encrypted free-space communications or unpredictable countermeasures.