UBC Theses and Dissertations
Creating ultrahigh intensities using a passive enhancement cavity Hammond, Thomas John
A table-top source for coherent extreme ultraviolet (EUV) radiation is beneficial for spectroscopic techniques requiring photon energies of more than a few electron volts. Other systems which can produce the required photon flux and photon energies are large and have limited beam time such as the Canadian Light Source or a free-electron laser. Conversely, conventional optics (lasers and crystals) cannot produce such high photon energies. An alternative method uses high harmonic generation, a technique that requires high intensities (> [formula omitted]). The high-order harmonics that are created retain temporal and spatial coherence, yet are now in the ultraviolet and soft X-ray region of the electromagnetic spectrum. The goal of this thesis was to design an optical source and amplifier system that created intensities which surpassed the threshold required for high harmonic generation. The approach used kept the bandwidth narrow and allowed for high EUV photon flux, useful for spectroscopy. Towards this end, a titanium-doped sapphire laser oscillator was designed and built to output > 1W average power, with a peak power > 100kW but limited in bandwidth to 2nm. The methods for obtaining such a high peak power - yet in a stable, bandwidth limited case - are presented. The laser output was then injected into an enhancement cavity with a high Q factor, increasing the average power by a factor of 50. The peak intensity has reached 4 x [formula omitted], or to within a factor of 2 of the threshold required to create EUV radiation. Lastly, methods for coupling out the EUV from the enhancement cavity are presented.
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