Keywords

Thulium fiber laser, chirped pulse amplification, spectral beam combining

Abstract

High power thulium fiber lasers are useful for a number of applications in both continuous-wave and pulsed operating regimes. The use of thulium as a dopant has recently gained interest due to its large bandwidth, possibility of high efficiency, possibility of high power and long wavelength ~1.8 – 2.1 μm. The longer emission wavelength of Tm-doped fiber lasers compared to Yb- and/or Er-doped fiber lasers creates the possibility for higher peak power operation due to the larger nonlinear thresholds and reduced nonlinear phase accumulation. One primary interest in Tm-doped fiber lasers has been to scale to high average powers; however, the thermal and mechanical constraints of the fiber limit the average power out of a single-fiber aperture. One method to overcome the constraints of a single laser aperture is to spectrally combine the output from multiple lasers operating with different wavelengths into a single beam. In this thesis, results will be presented on the development of three polarized 100 W level laser systems that were wavelength stabilized for SBC. In addition to the development of the laser channels, the beams were combined using bandpass filters to achieve a single near diffraction-limited output. Concurrently, with the development of high average power systems there is an increasing interest in femotosecond pulse generation and amplification using Tm- doped fiber lasers. High peak power sources operating near 2 µm have the potential to be efficient pump sources to generate mid-infrared light through supercontinuum generation or optical parametric oscillators. This thesis focuses on the development of a laser system utilizing chirped pulse amplification (CPA) to achieve record level energies and peak powers for ultrashort pulses in Tm-doped fiber. iv A mode-locked oscillator was built to generate femtosecond pulses operating with pJ energy. Pulses generated in the mode-locked oscillator were limited to low energies and contained spectral modulation due to the mode-locking mechanism, therefore, a Raman-soliton self-frequency shift (Raman-SSFS) amplifier was built to amplify pulses, decrease the pulse duration, and spectrally clean pulses. These pulses were amplified using chirped pulse amplification (CPA) in which, limiting factors for amplification were examined and a high peak power system was built. The primary limiting factors of CPA in fibers include the nonlinear phase accumulation, primarily through self-phase modulation (SPM), and gain narrowing. Gain narrowing was examined by temporally stretching pulses in a highly nonlinear fiber that both stretched the pulse duration and broadened the spectrum. A high peak power CPA system amplified pulses to 1 µJ energy with 300 fs compressed pulses, corresponding to a peak power >3 MW. High peak power pulses were coupled into highly nonlinear fibers to generate supercontinuum

Notes

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Graduation Date

2013

Semester

Spring

Advisor

Richardson, Martin

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

Optics and Photonics

Degree Program

Optics

Format

application/pdf

Identifier

CFE0004752

URL

http://purl.fcla.edu/fcla/etd/CFE0004752

Language

English

Release Date

May 2018

Length of Campus-only Access

5 years

Access Status

Doctoral Dissertation (Campus-only Access)

Subjects

Dissertations, Academic -- Optics and Photonics, Optics and Photonics -- Dissertations, Academic

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