Quantum cascade lasers are unipolar semiconductor lasers that offer a unique combination of compact size, high efficiency, high optical power, and flexibility to achieve a targeted emission wavelength with the same laser core material composition, employing so-called bandgap engineering. Since their invention in 1994, watt-level CW power with 5 to 20 % wallplug efficiency was demonstrated for QCLs throughout the entire 4 to 12 µm range, which makes QCLs very attractive for a number of practical applications. Our earlier work on broad-area QCLs emitting in the 4.6 µm to 5.7 µm spectral range demonstrated that CW power scaling with lateral device dimensions is an effective approach to increasing QCL power. First experimental and numerical data for short-wavelength ( < 4.2 µm) broad-area QCLs presented here show that this approach is very promising for achieving multi-watt CW operation in this challenging spectral region as well. Using optical power scaling with added lateral and longitudinal optical mode controls to achieve high spectral brightness is the other main topic of this dissertation. Two beam control methods for broad-area QCLs and results for single-mode devices with a short top-metal distributed Bragg reflector are presented. Finally, to improve laser reliability at high CW power, substrate-emitting configuration with a high spectral brightness and reduced beam divergence is demonstrated. These results pave the way for the development of ultra-compact and reliable infrared lasers with a high spectral brightness needed for a number of critical applications, including infrared countermeasures.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Sanchez Cristobal, Enrique, "High Spectral Brightness, Broad Area Quantum Cascade Lasers" (2021). Electronic Theses and Dissertations, 2020-. 925.