Date of Award

3-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Manuel R. Ferdinandus, PhD

Abstract

Two beam coupling (TBC) is a coherent interaction in which energy is transferred from one laser beam to another and has promising applications in real-time holography and coherent beam combing. We have recently shown efficient degenerate frequency TBC for counter-propagation geometries in isotropic two-photon absorbing media pumped with a nanosecond pulsed laser. When an interference pattern is generated in this media, single and two photon absorption initiates a population redistribution resulting in a holographic grating with the same modulation period and phase initially. However, due to temporal convolution of self- and cross-phase modulation, the grating will begin to shift in time relative to the interference pattern thus allowing coherent energy transfer to evolve. A comprehensive theoretical and numerical model is presented consistent with empirical results and historical observations of both energy and phase coupling. Numerical simulations indicate the presence self-oscillation due to nonlinear phase wrapping and strong excited state absorption inhibit energy transfer in a co-propagating geometry. However with proper temporal phase conditioning and choice of medium thickness, significant energy transfer can be achieved in the co-propagating case.

AFIT Designator

AFIT-ENP-DS-21-M-327

DTIC Accession Number

AD1145753

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