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Title:Thermal management of ytterbium-doped high-power fiber lasers
Author(s):Yu, Nanjie
Advisor(s):Dragic, Peter D.
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Thermal Management
High power fiber laser
Abstract:Theoretical and experimental investigation of two proposed thermal management approaches for high-power fiber lasers is presented. The first is an approach to reduce the amount of generated thermal energy by reducing the quantum defect (QD) in the system, which is the dominating process in an optimized fiber laser system. The second is an approach to extract thermal energy from the active fiber, which will balance the generated thermal energy and make it a radiation-balanced fiber laser. To achieve the first approach, six Yb-doped multicomponent fluorosilicate fibers were fabricated and investigated. With experimental characterization of the refractive index profile, thermo-optic coefficient, ytterbium spectroscopy, and Raman and Brillouin scattering, these fibers were found to be suitable for low QD operation. By experimentally setting up a Fabry-Perot cavity laser, QD of less than 1% and slope efficiencies near 70% are achieved, which are limited by splice and background losses in the fiber. Simulations on a power amplifier stage with a double-clad version of the fiber were performed and slope efficiency near 80% is expected. To achieve the second approach, four fibers fabricated by chemical vapor deposition are investigated. A vacuum-environment, contactless measurement method is designed based on the temperature dependence of Brillouin scattering from the fiber. Although no cooling was observed in the fiber so far, the analysis here serves as an important basis for further fiber and experimental design.
Issue Date:2019-12-05
Rights Information:Copyright 2019 Nanjie Yu
Date Available in IDEALS:2020-03-02
Date Deposited:2019-12

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