Abstract
Extreme ultraviolet microscopy and wavefront sensing are key elements for next-generation ultrafast applications, such as chemically-resolved imaging, focal spot diagnostics in pump-and-probe experiments, and actinic metrology for the state-of-the-art lithography node at 13.5 nm wavelength. Ptychography offers a robust solution to the aforementioned challenges. Originally adapted by the electron and synchrotron communities, advances in the stability and brightness of high-harmonic tabletop sources have enabled the transfer of ptychography to the laboratory. This review covers the state of the art in tabletop ptychography with high harmonic generation sources. We consider hardware options such as illumination optics and detector concepts as well as algorithmic aspects in the analysis of multispectral ptychography data. Finally, we review technological application cases such as multispectral wavefront sensing, attosecond pulse characterization, and depth-resolved imaging.
Highlights
The ability to perform tabletop extreme ultraviolet (XUV) microscopy is a longstanding scientific challenge
The scientific complementary metal–oxide–semiconductor (sCMOS) architecture allows for enormous frame rates up to 74 Hz for 4 megapixel images, which is more than two orders of magnitude faster as compared to XUV Charge-coupled devices (CCDs)
In addition to the need for quantitatively accurate imaging tools, the two main technical ingredients that have enabled the emergence of XUV tabletop ptychography, are the rapid development of coherent imaging techniques, and the significant advances in coherent flux generation from high harmonic generation (HHG) sources in the last decade
Summary
The ability to perform tabletop extreme ultraviolet (XUV) microscopy is a longstanding scientific challenge. While there exists a plethora of source concepts for the generation of XUV radiation, the principle of high harmonic generation (HHG) [4,5] arguably outperforms other techniques available to date in terms of coherent photon flux [6,7,8]. Ptychography is a lensless imaging technique, meaning that no imaging optics are required downstream of a sample under investigation, which considerably facilitates the experimental geometry and flux efficiency as compared to lens-based XUV microscopy setups. It inherently exploits amplitude and phase contrast, which enables a quantitative investigation of material properties, a capability that many competing imaging techniques lack. The article closes with future opportunities and challenges in compact XUV ptychography (see section 5)
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