Building a laboratory based XUV microscope

Abstract

High harmonic generation (HHG) is a non-linear interaction between a driving laser pulse and a target gas. The result of this process is the generation of coherent extreme ultraviolet (XUV) and soft X-ray radiation at harmonic frequencies of the driving laser. There are several uses for this source including attosecond time resolved spectroscopy and nanoscale imaging which this thesis will focus on.

The work contained within this thesis begins by investigating the development of capillary based HHG by comparison of the experimentally observed propagation of the driving laser pulse to both a linear ionisation based model and a multimode non-linearSchrodinger equation model. Manufacture, mounting and coupling into the capillary are described. A simple linear model of propagation along the capillary is compared to experimental measurements of fluorescence along the capillary showingthe presence of mode beating. The model is extended to a non linear propagation model and validated against the spatio spectral output of the capillary.

The second half of the thesis takes the XUV output from a gas cell and uses it for a coherent diffractive imaging experiment (CDI). The development of the imaging setup is described before presenting the results of a preliminary CDI experiment with a binary test sample and a polychromatic beam. Accurate measurement of the XUV beam focal position was determined by recording diffraction through a binary array of apertures. Results of a CDI experiment demonstrating a resolution of better than 200 nm is shown for a polychromatic beam with an algorithm designed for a monochromatic source.

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Identifiers

ORCID for Jeremy G. Frey: orcid.org/0000-0003-0842-4302

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