BORIS Theses

BORIS Theses
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Time-Domain Ptychography and its Applications in Ultrafast Science

Schweizer, Tobias (2021). Time-Domain Ptychography and its Applications in Ultrafast Science. (Thesis). Universität Bern, Bern

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Time-Domain Ptychography (TDP) is a relatively new approach to iteratively solve the phase retrieval problem. It was introduced in 2015 as a tool to characterise ultrashort laser pulses and has gained a considerable amount of popularity since then. Compared to the well established FROG-like algorithms, TDP is much more data-efficient. After examining the ptychographic model in terms of both projection-based and gradient-based algorithms and comparing possible implementations, the Thesis explores three applications of TDP. First, the characterisation capablilties of TDP are extended into vector-fields, thus allowing for the reconstruction of time-dependent polarisation states of ultrashort laser pulses. The new td-vPIE algorithm is tested against a large set of synthetic data and its accuracy is verified in a set of simple experiments with both constant and time-varying polarisation states. Moving away from characterisation, TDP is applied to SFG spectroscopy, specically the spectroscopy of vibrational modes of surface polymers. A short summary of the mathematical model and its connection to ptychography is given, and the approach is tested in a set of simulations. The findings are verfied with a set of measurements of the vibrational response of octadecanethiol (ODT) on a gold substrate. Finally, an excursion into the realm of attosecond physics is made. The use of TDP as a diagnostics tool to characterise FEL pulses from electron streaking traces is discussed, and after providing a mathematical relationship between streaking traces and ptychograms, the possibility of single-shot FEL pulse characterisation is explored. Later on TDP is used beyond characterisation, namely to estimate the time delay between the 2s and 2p photoelectron emissions in neon using data obtained at the Max Planck Institute for the Structure and Dynamics of Matter.

Item Type: Thesis
Dissertation Type: Single
Date of Defense: 6 October 2021
Subjects: 500 Science > 540 Chemistry
Institute / Center: 08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)
Depositing User: Hammer Igor
Date Deposited: 23 Dec 2022 08:41
Last Modified: 24 Dec 2022 01:30

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