6/9/2008
Dissertation Abstract & Announcement of Dissertation Defense: Leo Siiman
Announcing the Final Examination of Leo Siiman for the Degree of Doctor of Philosophy in Optics Dissertation title: "ULTRASHORT LASER PULSE INTERACTION WITH PHOTO-THERMO-REFRACTIVE GLASS" Photo-thermo-refractive (PTR) glass is a photosensitive material useful for volume hologram recording. It is an optical quality multi-component silicate glass that demonstrates all the advantages of conventional optics; thermal stability, high laser damage threshold, and a wide transparency range. Moreover, the ability to record phase patterns (i.e. refractive index changes) into this glass has allowed for the fabrication of volume holograms with diffraction efficiency greater than 99%. The conventional method of recording a hologram in PTR glass relies on exposure to continuous-wave ultraviolet laser radiation. The interaction between infrared ultrashort laser pulses and PTR glass is studied in this dissertation. It is shown that photosensitivity in PTR glass can be extended from the UV region to longer wavelengths (near-infrared) by exposure to short laser pulses. The features of nonlinear photosensitivity are experimentally investigated for laser wavelengths ranging from 1.5 to 0.8 mm and explained by a special case of multiphoton ionization in transparent dielectrics. Phase optical elements are recorded in PTR glass by exposure to IR femtosecond laser pulses. The interaction of ultrashort laser pulses with volume holograms recorded in PTR glass is studied in two intensity regimes. At intensities below ~1012 W/cm2 properties such as diffraction efficiency, angular divergence, selectivity, and pulse front tilt are shown to agree with classical linear diffraction theory for broad spectral width lasers. At higher intensities, nonlinear generation of third harmonic is observed. Three separate conditions for third harmonic generation and diffraction by a volume hologram in PTR glass are explained theoretically. Outline of Studies:Major: OpticsEducational Career:B.S. in Electrical & Computer Engineering, University of Florida, Gainesville Committee in Charge:Dr. Boris Y. Zeldovich, ChairDr. Leonid B. Glebov, Co-chairDr. Michael BassDr. David HaganDr. Alfons Schulte Approved for distribution by Dr. Boris Zeldovich, Committee Chair, on May 23, 2003. The public is welcome to attend.
