Giving to CREOL
CREOL, The College of Optics & Photonics

Final Examination of Matthew Weidman for the Degree of Doctor of Philosophy in Optics

Friday, November 2, 2012 10:30 AM to 12:30 PM
CREOL Room 102

Dissertation Title:
Laser Filamentation Interaction with Materials for Spectroscopic Applications

Laser filamentation is a non-diffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work has shown a quasi-constant filament-induced mass ablation along a 35 m propagation distance. The mass ablated was sufficient for the application of laser filamentation as a sampling tool for plasma based spectroscopy techniques. Within the scope of this study, single-shot ablation was compared with multi-shot ablation. The dependence of ablated mass on the number of pulses was observed to have a quasi-linear dependence on the number of pulses, advantageous for applications such as spectroscopy. Sample metrology showed that both physical and optical material properties have significant effects on the filament-induced ablation behavior.

A relatively slow filament-induced plasma expansion was observed, as compared with a focused beam. This suggests that less energy was transferred to the plasma during filament-induced ablation. The effects of the filament core and the energy reservoir on the filament-induced ablation and plasma formation were investigated. Goniometric measurements of the filament-induced plasma, along with radiometric calculations, provided the number of emitted photons from a specific atomic transition and sample material.

This work has advanced the understanding of the effects of single filaments on the ablation of solid materials and the understanding of filament-induced plasma dynamics. It has laid the foundation for further quantitative studies of multiple filamentation. The implications of this work extend beyond spectroscopy and included any application of filamentation that involves the interaction with a solid material.

Major:  Optics

Educational Career:
BS: 2006,  Oregon Institute of Technology
MS:   2007,  University of Central Florida

Committee in Charge:
Dr. Martin Richardson (Chair)
Dr. Demetrios Christodoulides
Dr. Axel Schulzgen
Dr. Michael Sigman

Approved for distribution by Dr. Martin Richardson, Committee Chair, on 10/19/2012.
The public is welcome to attend.

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