EUV Microscopy with a Tabletop High Harmonic Generation Source: Generalizing Coherent Diffractive Imaging to Extended Samples in Transmission, Reflection, and Hyperspectral Modalities

Bosheng Zhang, University of Colorado at Boulder


Imaging at the nanoscale is of great interest for applications in materials science, nanoscience and biology. The microscopy method developed in this thesis combines a tabletop coherent EUV/X-ray source based on high harmonic generation, and an image-forming method based on coherent diffractive imaging. This microscopy method offers truly diffraction-limited resolution; however, previous work has been limited to thin, isolated samples in transmission mode. This thesis work extends this tool for imaging non-isolated samples, and for working in reflection mode to image surface features of thick samples. The quantitative phase information of the reflection image enables surface profilometry capability with sub-nanometer precision. The microscope developed in this work is also demonstrated to have hyperspectral capability with simultaneous multi-wavelength illumination, without the need for wavelength scanning or energy-resolved detectors. In the future, by taking advantage of the short-pulse nature of the high harmonic illumination, this microscope will be able to image nanoscale ultrafast dynamics with 10 femtosecond temporal resolution, opening the door for imaging at the space-time limits.