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.
O. Spitz, J. Wu, S. Khanal, M. Carras, B. S. Williams, C. W. Wong, and F. Grillot, "Temperature dependence of a mid-infrared quantum cascade laser with external optical feedback," Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV, 105401N (Presented at SPIE OPTO: January 31, 2018; Published: 26 January 2018); https://doi.org/10.1117/12.2290117.
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