Date of Award

9-13-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

David E. Weeks, PhD

Abstract

This research focused on the numeric simulation of unstable laser resonators with high gain media. In order to accomplish the research, the modes and eigenvalues for various bare cavity resonator were computed followed by modes of a resonator in the presence of gain. Using a Fourier Split Step Method in a Fox and Li iteration scheme, different laser outputs for various laser cavities with gain were computed. Various parameters defining positive branch confocal unstable resonators were chosen corresponding to four studies. The four studies focused on modifying laser cavity Fresnel number, gain medium parameters, gain cell position, and gain cell length from a baseline laser cavity geometry. It was observed that the highest laser cavity efficiencies occurred when the laser cavity had a Fresnel number greater than 7 and was positioned at the back larger mirror of an unstable resonator. Longer gain cell lengths were found to correspond to higher beam qualities. Beam quality was found to be inversely related to laser efficiency. A theory for modifying simple laser models based upon a mode volume was derived and supported the results of the gain wave-optic simulations.

AFIT Designator

AFIT-ENP-DS-19-S-024

DTIC Accession Number

DTIC Pending

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