Abstract:
High-power fiber laser systems enjoy a widespread use in manufacturing, medical, and defense applications as well as scientific research, due to their remarkable power scalability, high electrical to optical efficiency, compactness and ruggedness. However, single-mode fiber power scaling has stagnated in the past years, primarily due to the onset of nonlinear effects such as stimulated Brillouin/Raman scattering and transverse modal instabilities.
This thesis addresses the analysis and mitigation of transverse modal instabilities in high-power fiber amplifiers. I describe the high-power fiber amplifier testbed that I set up to test fibers fabricated in house. I will show our results of a Yb-doped fiber amplifier with more than 2.2kW signal power and beam quality of 1.2 M2. In consequence, I demonstrate mode-selective amplification in a large mode-area Yb-doped fiber using a 3-mode photonic lantern. All three modes were amplified to above 4W with OSNRs higher than 16dB. In addition, I show a novel high-speed beam analysis technique to study transverse modal instabilities. To guide simulation-aided fiber designs, I developed a GPU accelerated simulation suite to study the dynamics that occur in these high-power fiber amplifiers. A 64x64 spatial grid, with 6000 time- and 20000 distance-steps can be solved at 12 min/meter on a GeForce GTX 1080 Ti. Based on these simulations, I will show dynamic transverse modal instability mitigation strategies that rely on mode modulation.
Major: Optics and Photonics
Educational Career:
BS: 2011, Physics, Jacobs University Bremen, Germany
MS: 2013, Optics and Photonics, Karlsruhe Institute of Technology, Germany
MS: 2019, Optics and Photonics, CREOL, University of Central Florida
Committee in Charge:
Dr. Rodrigo Amezcua Correa (Chair)
Dr. Axel Schulzgen
Dr. Miguel Bandres
Dr. Lawrence Shah
Approved for distribution by Dr. Rodrigo Amezcua Correa, Committee Chair, on November 5, 2020.
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