Extreme Ultraviolet Ptychographic Microscopy

Projektinformationen

XUVPM

ID Finanzhilfevereinbarung: 101153960

DOI

10.3030/101153960

Projekt abgeschlossen

EK-Unterschriftsdatum 12 März 2024

Startdatum 1 Mai 2024

Enddatum 30 April 2026

Finanziert unter

• Marie Skłodowska-Curie Actions (MSCA)

Gesamtkosten

Keine Daten

EU-Beitrag

€ 222 727,68

Koordiniert durch

LUNDS UNIVERSITET
Sweden

Periodic Reporting for period 1 - XUVPM (Extreme Ultraviolet Ptychographic Microscopy)

Berichtszeitraum: 2024-05-01 bis 2026-04-30

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

New-generation electronic, quantum, and semiconductor devices are becoming increasingly complex and continuously shrinking in size. Characterizing such structures at the nanoscale requires imaging techniques that combine extremely high spatial resolution with sensitivity to material composition. Extreme ultraviolet (XUV) ptychography is a highly promising microscopy technique capable of meeting these requirements. However, current tabletop XUV ptychographic microscopes still face significant challenges in terms of spatial resolution, robustness, and available photon flux.

The Extreme Ultraviolet Ptychographic Microscopy (XUVPM) project aims to address these challenges by developing novel structured illumination sources for XUV ptychography. The core approach is based on high-order harmonic generation (HHG), driven by tailored laser beams, to create structured XUV beams with controllable spatial properties. In particular, the project explores the use of light carrying orbital angular momentum (OAM) as illumination for ptychographic microscopy. Such structured light is expected to improve the robustness of image reconstruction and enhance spatial resolution.

To realize this vision, the project combines expertise in ultrafast optics, HHG, structured light, and computational imaging. A two-color HHG setup was established, enabling flexible control of the driving laser beams through individual spatial light modulators (SLMs). The generated XUV radiation was then intended to be integrated into a newly designed ptychographic microscope.

During the course of the project, some methodological aspects were adjusted in response to scientific findings. Nevertheless, the overall objective remained unchanged: to advance the tabletop XUV ptychographic microscopy through the development and investigation of novel structured XUV illumination schemes. In the long term, the knowledge generated by this project is expected to contribute to future imaging solutions for advanced semiconductor and quantum technologies, while strengthening Europe's leadership in attosecond science and high-resolution microscopy.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

The project successfully established a highly versatile two-color high-order harmonic generation (HHG) setup based on an industrial-grade femtosecond laser system. The setup integrates two spatial light modulators (SLMs), enabling independent wavefront shaping of the driving laser beams and the flexible generation of structured light fields. This experimental platform and its performance have already resulted in scientific publications.

Experimental studies were carried out to optimize the XUV yield in the two-color HHG configuration. By systematically investigating the influence of the relative phase and intensity ratio between the two driving colors, the optimal conditions for maximizing harmonic generation efficiency were identified.

A new vacuum chamber was established, and a compact transmission ptychographic microscope was designed. The microscope incorporates XUV spectral filtering and focusing optics, precision sample positioning, and XUV detection. A three-mirror focusing configuration based on the Schiefspiegler principle was designed to minimize optical aberrations while preserving photon flux.

During the course of the project, a new research direction emerged based on the use of higher-radial-order Laguerre–Gaussian (LG) beams. A two-donut orbital angular momentum (OAM) beam was designed and investigated. To the best of our knowledge, such OAM beams had not previously been employed for HHG. Numerical simulations demonstrated that this beam can generate structured XUV radiation suitable for ptychographic applications.

The project also successfully demonstrated the generation of two-donut OAM laser beams and high harmonics experimentally. In addition, significant effort was devoted to designing a differential pumping system capable of simultaneously maintaining low pressure in the application chamber while transmitting highly divergent OAM-XUV beams.

Comprehensive ptychography simulations were performed to compare conventional Gaussian illumination with two-donut OAM illumination. The simulation results showed that two-donut OAM probes can improve image contrast and reduce the number of required scan positions, thereby enhancing spatial resolution and shortening image acquisition times.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

The project has achieved several results that advance the state of the art in HHG and tabletop XUV ptychographic microscopy.

First, a highly flexible two-color HHG setup equipped with two SLMs was successfully developed, enabling comprehensive control over the spatial properties of the generated XUV radiation. This capability opens up new opportunities for designing tailored illumination schemes suitable for advanced imaging applications.

Second, the project introduced a novel structured illumination concept based on higher-radial-order LG beams, specifically a two-donut orbital angular momentum (OAM) mode. To the best of our knowledge, this type of OAM beam has not previously been employed for HHG. Numerical studies indicate that these structured probes can improve ptychographic performance by enhancing image quality while reducing data acquisition requirements.

Third, the project completed the full design of an XUV ptychographic microscope optimized for structured illumination. Although full experimental ptychographic imaging with OAM illumination could not be achieved within the project duration, the successful generation and characterization of OAM high harmonics, together with simulation results, provide strong evidence for the feasibility and potential advantages of this approach.

These results lay the foundation for future research aimed at experimentally implementing structured-light XUV ptychography and further improving the spatial resolution of tabletop XUV ptychographic microscopes. Follow-up work will focus on achieving full experimental realization, validating the predicted performance improvements, and further optimizing structured XUV light sources. In the long term, these developments may contribute to driving the development of next-generation imaging technologies for semiconductor metrology, nanotechnology, and quantum device characterization.