%0 Journal Article %T Extensive study of the linewidth enhancement factor of a distributed feedback quantum cascade laser at ultra-low temperature %+ MirSense %+ Télécommunications Optiques (GTO) %+ Département Communications & Electronique (COMELEC) %+ Technische Universität Darmstadt - Technical University of Darmstadt (TU Darmstadt) %+ Laboratoire Traitement et Communication de l'Information (LTCI) %+ The University of New Mexico [Albuquerque] %A Spitz, Olivier %A Herdt, Andreas %A Duan, Jianan %A Carras, Mathieu %A Elsässer, Wolfgang %A Grillot, Frederic %Z SPIE OPTO, 2019, San Francisco, California, United States %< avec comité de lecture %@ 0277-786X %J Proceedings of SPIE, the International Society for Optical Engineering %I SPIE, The International Society for Optical Engineering %S Quantum Sensing and Nano Electronics and Photonics XVI %V 10926 %P 42 %8 2019-02 %D 2019 %R 10.1117/12.2510502 %K Linewidth enhancement factor %K Alpha factor %K Mid-infrared photonics %K Quantum cascade lasers %Z Engineering Sciences [physics]/Optics / PhotonicJournal articles %X Quantum cascade lasers (QCLs) are optical sources exploiting radiative intersubband transitions within theconduction band of semiconductor heterostructures. The opportunity given by the broad span of wavelengthsthat QCLs can achieve, from mid-infrared to terahertz, leads to a wide number of applications such as absorptionspectroscopy, optical countermeasures and free-space communications requiring stable single-mode operationwith a narrow linewidth and high output power. One of the parameters of paramount importance for studyingthe high-speed and nonlinear dynamical properties of QCLs is the linewidth enhancement factor (LEF). TheLEF quanties the coupling between the gain and the refractive index of the QCL or, in a similar manner, thecoupling between the phase and the amplitude of the electrical field. Prior work focused on experimental studiesof the LEF for pump currents above threshold but without exceeding 12% of the threshold current at 283Kand 56% of the threshold current at 82K. In this work, we use the Hakki-Paoli method6 to retrieve the LEF forcurrent biases below threshold. We complement our ndings using the self-mixing interferometry technique toobtain LEFs for current biases up to more than 100% of the threshold current. These insets are meaningful tounderstand the behavior of QCLs, which exhibit a strongly temperature sensitive chaotic bubble when subjectto external optical feedback. %G English %2 https://telecom-paris.hal.science/hal-02342862v2/document %2 https://telecom-paris.hal.science/hal-02342862v2/file/SpitzPhotonicsWestSPIE.pdf %L hal-02342862 %U https://telecom-paris.hal.science/hal-02342862 %~ INSTITUT-TELECOM %~ ENST %~ TELECOM-PARISTECH %~ PARISTECH %~ UNIV-PARIS-SACLAY %~ TELECOM-PARISTECH-SACLAY %~ LTCI %~ COMELEC %~ GTO %~ INSTITUTS-TELECOM