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 2.2 kW signal power and beam quality of 1.1 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 4 W with OSNRs higher than 16 dB. In addition, I show a novel high-speed beam analysis technique to study transverse modal instabilities. To guide fiber designs, I developed a GPU accelerated simulation suite to study the dynamics that occur in high-power fiber amplifiers. A 64 x 64 spatial grid, with 6000 time- and 20000 distance-steps can be solved at 2 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.

Notes

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Graduation Date

2020

Semester

Fall

Advisor

Amezcua Correa, Rodrigo

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

Optics and Photonics

Degree Program

Optics and Photonics

Format

application/pdf

Identifier

CFE0008789;DP0025520

URL

https://purls.library.ucf.edu/go/DP0025520

Language

English

Release Date

June 2021

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

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