Supervisor's Foreword; Abstract; Preface; Preface; Journal Publications; Invited Conference Presentations; Conference Presentations; Acknowledgements; Contents; Acronyms; 1 Introduction; 1.1 The Need for Mid-infrared Sources; 1.1.1 Applications at Mid-infrared Wavelengths; 1.1.2 Available Mid-infrared Sources; 1.2 Organization of the Dissertation; References; 2 Quantum Cascade Lasers: High Performance Mid-infrared Sources; 2.1 Principle of Operation; 2.2 Theory; 2.2.1 Heterostructure; 2.2.2 Spontaneous Emission and Material Gain Calculation; 2.2.3 QCL Rate Equations

3.3.7 Extension to the Dynamics of a Class-A Laser Under Optical Feedback3.3.8 Chaotic Laser Diodes and Applications; 3.4 Conclusions; References; 4 Impact of Optical Feedback on Quantum Cascade Lasers; 4.1 Previous Studies; 4.2 Experimental Setup; 4.3 Numerical Model; 4.4 Linewidth Enhancement Factor Measurement; 4.4.1 Wavelength Shift with Optical Feedback; 4.4.2 Self-mixing Interferometry; 4.4.3 Gain Compression Coefficient; 4.5 Influence of the Optical Feedback on the QCL L-I Characteristic Curves; 4.5.1 Case of the DFB QCL; 4.5.2 Case of the Fabry-Perot QCL

4.5.3 Optical Feedback from a Mid-infrared Fiber4.6 Feedback Regimes in a Mid-infrared QCL; 4.6.1 Optical Spectra of a QCL Under Optical Feedback; 4.6.2 Feedback Cartography of the DFB QCL; 4.7 Nonlinear Dynamics and Chaos in a QCL Under Optical Feedback; 4.7.1 Time Series and Electrical Spectra; 4.7.2 Low Frequency Fluctuations; 4.7.3 Experimental Bifurcation Diagram; 4.7.4 Numerical Bifurcation Diagram; 4.7.5 Consequences of the Possible Chaotic Operation of a QCL; 4.8 Conclusion; References; 5 Beam Shaping in Broad-Area Quantum Cascade Lasers Using Optical Feedback; 5.1 Motivations