Coherent EUV Light from High-Order Harmonic Generation: Enhancement and Applications to Lensless Diffractive Imaging

The first half of this thesis presents the first demonstration of quasi-phase matching
in the coherent high-order harmonic conversion of ultrafast laser pulses into the
EUV region of the spectrum. To achieve this quasi-phase matching, a novel method of
fabricating hollow waveguides with a modulated inner diameter was developed. This
technique lead to significant enhancements of EUV flux at wavelengths shorter than
were previously accessible by known phase-matching techniques. In the second half of
this thesis, the first tabletop demonstration of lensless diffractive imaging with EUV
light is presented using HHG in a gas-filled hollow waveguide to provide coherent illumination.
This tabletop microscope shows a spatial resolution of ∼ 200 nm and a large
depth of field. Furthermore, the technique is easily scalable to shorter wavelengths of
interest to biological imaging.