Manipulation and application of laser light using spatial light modulation
Sammanfattning: Attosecond pulses obtained via high harmonic generation often suffer from chromatic aberration. This is inherent from the generation process as a consequence of the spatial profile of the driving laser pulses. Consequently, the focus positions and divergences of consecutive harmonics vary, leading to chromatic aberration which prevents high-quality refocusing as is critically required for applications. The aim of this project is to develop a way of diminishing this chromatic aberration through spatial phase manipulation of the driving laser pulses. This is done through use of a spatial light modulator in conjunction with a phase-retrieval and beam-shaping program which was developed during the project. Harmonic spectra and driving beam foci are recorded with an extreme ultraviolet spectrometer and an infrared-sensitive camera, respectively. It is shown that the spatial light modulator in conjunction with the written program can successfully correct aberrated beams, leading to an increase in peak intensity and a decrease in beam width near the focus. However, reducing the divergence of generated harmonics through beam shaping turned out to be complicated. It was concluded that the ability to measure the average harmonic intensities and peak intensities of the driving field over several iterations during the experiment is a necessary step. Additionally, different types of focus-improving techniques, such as other phase-retrieval algorithms and Zernike optimization could be used in future iterations to potentially improve focus correction, which would assist beam shaping.
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