Development of a petawatt class Ti:Sapphire laser for the excitation of extreme radiation sources
Date
2020
Authors
Rockwood, Alex Pratt, author
Rocca, Jorge J., advisor
Lee, Siu Au, committee member
Roberts, Jacob L., committee member
Marconi, Mario C., committee member
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Abstract
This dissertation describes the design, construction and characterization of a high peak power, high repetition rate, Titanium-Sapphire laser system. This chirped-pulse amplification (CPA) laser delivers femtosecond pulses of up to 0.85 PW peak power. By utilizing pump laser amplifiers with a slab configuration high repetition rate are achieved, 3.3Hz, the highest at which Petawatt-class lasers have been operated to date. This 800nm laser also has a high power, ultra-high contrast 400 nm beamline. By frequency doubling the 800 nm with a KDP crystal at ≥ 40% conversion we are able to achieve a contrast of > 1 × 10-12. The ability to focus this second harmonic beam to ~1.2 μm Full Width at Half Maximum (FWHM) spot size made it possible to achieve intensities up to ~ 6.5 ×1021 W/cm2. With these high intensities and high contrast this laser is a powerful tool in many applications especially in the study of laser/matter interactions at relativistic plasmas. This Ti:Sapphire laser was used for the excitation of plasma based soft x-ray (SXR) lasers. prior to this work compact, repetitively fired, gain-saturated x-ray lasers had been limited to wavelengths above λ = 8.85 nm. We were able to demonstrate SXR lasers operating in the gain-saturated regime down to wavelengths as low as λ = 6.85 nm in Ni-like Gd. Gain was also observed at λ = 6.4 nm, and λ = 5.8 nm in Ni-like Dy. As an application of plasma-based SXR lasers, single shot Fourier holograms covering a large area of view were demonstrated using an 18.9nm laser with high spatial coherence based on dual plasma amplifier. Compact SXR lasers have made possible applications in nano-scale imaging, dense plasma diagnostics and a variety of new studies of materials and surfaces. Other applications that were enabled by this Petwatt-class laser discussed elsewhere include the study of the interaction of relativistic laser pulses with aligned nanostructures, producing record conversion efficiency of optical laser light into picosecond x-ray pulses with photons of > 1 KeV energy and flashes of deuterium-deuterium fusion neutrons.
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Subject
lasers
soft x-ray lasers
holography
x-ray lasers
petawatt