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Exploring multi-wavelength single-shot Fourier ptychography (SSFP) as a technique for ultrafast pulsed laser (UPL) characterization
Larsen, Rhiannon R.
Larsen, Rhiannon R.
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2023
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Abstract
Ultra-fast pulsed laser (UPL) applications are reaching beyond the expert realm of research and gaining relevance in industrial manufacturing for high-precision material processing. This transition makes it all the more important for simple and affordable UPL characterization methods to be developed. My work sets the stage for the implementation of a new, low-cost method for phase and amplitude retrieval in broadband spatio-temporal signals. Single-shot Fourier ptychography uses Fourier properties and analysis to translate between the intensity profile and spectra of a series of uniquely filtered copies of an input field. The sophisticated computational software is paired with a modified, simple 4f imaging system, to collect all of the necessary data in a single ``shot." A pulse can be represented by a superposition of electro-magnetic waves, truncated in time. By the Heisenberg uncertainty principle, this broadens the spectrum, comprising a continuum of wavelengths within a bandwidth, which is often represented as a distribution of multiple discrete wavelengths in a histogram. By successfully retrieving both the phase and amplitude of two discrete wavelengths using SSFP, I present my work as a proof-of-concept toward an exciting new way for non-experts to characterize UPLs.
In this thesis I will introduce readers to computational imaging via Fourier ptychography, and provide the details regarding system design, algorithm functionality, laboratory implementation, single and multi-wavelength reconstruction results and suggested next steps. With the groundwork laid, I hope to inspire others to demonstrate successful UPL reconstructions with SSFP.
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