Table-top XUV nanoscope

Abstract

This thesis documents the development of a table-top extreme-ultraviolet (XUV) nanoscope suitable for coherent diffractive imaging (CDI). Intense spatially coherent ultrashort XUV and X-ray pulses are desired for nanoscale biological and material imaging. Such radiation can be produced via high harmonic generation (HHG) by focusing a highly intense ultrashort laser pulse into gas. In order to obtain high flux XUV radiation suitable for CDI, various generation conditions are explored. By observing the fluorescence from an argon gas jet to position the laser focus into different regions within the jet, a fourfold variation in XUV yield is achieved. Maximum output flux is obtained for the 19th harmonic when the laser is focused into the Mach disc of the jet. To further increase the XUV flux, HHG from a larger generation region (an argon-filled pipe) is also demonstrated. The most intense harmonic is nearly fifty times more intense and 10 nm shorter in wavelength compared with the most intense harmonic generated from an argon gas jet. Position for maximum generated XUV flux occurs when the laser focus is positioned after the pipe. In addition, a reduction in the number of harmonics in the output spectrum is also achieved by positioning the laser focus after the pipe. Using the high harmonics generated from the argon-filled pipe for XUV scattering, CDI is used to reveal the nanoscale structure of micron-sized objects. This thesis demonstrates the imaging of a 5 µm pinhole, a 7.5 µm FIB (focused ion beam) sample and a biological sample using the table-top XUV nanoscope. A maximum reconstructed object resolution of ~ 300 nm is achieved. The work described here will aid in the development of a table-top nanoscope capable of routine imaging.

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Identifiers

ORCID for James Grant-Jacob: orcid.org/0000-0002-4270-4247

ORCID for W.S. Brocklesby: orcid.org/0000-0002-2123-6712

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