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978-3-8439-0067-6, Reihe Physik
Dauerstrich-Festkörperlaser im tief-ultravioletten Spektralbereich
146 Seiten, Dissertation Universität Hamburg (2011), Softcover, A5
In recent years, considerable interest has emerged for the development of continuous-wave (cw) coherent light sources emitting within the deep ultraviolet (DUV) spectral range. For several applications such as defect detection in semiconductor manufacturing, material processing, biophotonics, as well as quantum optics DUV lasers with low cost, long lifetimes, and high electrical-to-optical efficiencies are essential. The objective of this thesis is the development of new radiation sources that meet these requirements.
Ce3+, as well as Pr3+-doped fluoride materials such as LiCaAlF6 were grown employing the Czochralski method. One focus was the development and optimization of the existing crystal growth facility for fluoride materials at the Institute of Laser-Physics of the University of Hamburg. By using an argon-CF4 gas mixture as growth atmosphere, oxide inclusions in the fluoride crystals were reduced and considerably higher optical quality could be achieved.
DUV laser sources with wide tunability can be realized by efficient 5d → 4f transitions in Ce3+-doped solid-state hosts. Therefore, a number of Ce-doped materials were manufactured and analyzed spectroscopically. Investigations on Ce-doped Al2O3 films fabricated via Pulsed Laser Deposition showed a promising efficient broadband fluorescence in the blue and green spectral range. The most promising candidate for tunable cw laser operation in the DUV spectral range was found to be Ce3+:LiCaAlF6.
In order to obtain laser action in Ce3+:LiCaAlF6 crystals, pump lasers with high output powers of about 2W at wavelengths around 266nm are required. Since such laser sources are commercially not available, the predominant task was the development of own DUV emitting pump sources. Therefore, intracavity frequency-doubled Pr3+-lasers were designed and characterized. In experiments with laser diode pumped Pr3+:LiYF4 crystals, slope efficiencies of up to 64 % and optical-optical efficiencies of up to 45 % were achieved in the visible spectral range. The outcoupled laser power was up to 938 mW for an absorbed pump power of about 1.5W. These are the world’s most efficient cw Pr3+- doped solid-state lasers. Additionally, laser diode pumped Pr3+:LiYF4 laser activity at 545.9 nm was demonstrated for the first time. Using intracavity frequency doubling laser output powers of 365 mW at 261.3 nm, as well as 426 mW at 319.8 nm were achieved. The demonstrated lasers are currently the most efficient and compact lasers in the ultraviolet spectral range.