Abstract

Thulium- and holmium-doped fiber lasers (TDF and HDF) emitting at 2 micron offer unique benefits and applications compared to common ytterbium-doped 1 micron lasers. This dissertation details the concepts, limitations, design, and performance of four 2 micron fiber laser systems. While these lasers were developed for various end-uses, they also provide further insight into two major power scaling limitations. The first limitation is optical nonlinearities: specifically stimulated Brillouin scattering (SBS) and modulation instability (MI). The second limitation is thermal failure due to inefficient pump conversion. First, a 21.5 W single-frequency, single-mode laser with adjustable output from continuous-wave to nanosecond pulses is developed. Measuring the SBS threshold versus pulse duration enables the Brillouin gain coefficient and gain bandwidth to be determined at 2 micron. Second, a 23 W spectrally-broadband, nanosecond pulsed laser is constructed for materials processing applications. The temporally incoherent multi-kW peak power pulses can also efficiently produce MI and supercontinuum generation by adjusting the input spectral linewidth. Third, the measured performance of in-band pumped TDF and HDF lasers are compared with simulations. HDF displays low efficiencies, which is explained by including ion clustering in the simulations. The TDF operates with impressive >90% slope efficiencies. Based on this result, a system design for >1 kW average power TDF amplifier is described. The designed final amplifier will be in-band pumped to enable high efficiency and low thermal load. The amplifier efficiency, operating bandwidth, thermal load, and nonlinear limits are modeled and analyzed to provide a framework for execution. Overall, this dissertation provides further insight and understanding on the various processes that limit power scaling of 2 micron fiber lasers.

Graduation Date

2018

Semester

Fall

Advisor

Richardson, Martin

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

CFE0007374

URL

http://purl.fcla.edu/fcla/etd/CFE0007374

Language

English

Release Date

December 2023

Length of Campus-only Access

5 years

Access Status

Doctoral Dissertation (Campus-only Access)

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