Microscopy with extreme ultraviolet (EUV) radiation holds promise for high-resolution imaging with excellent material contrast, due to the short wavelength and numerous element-specific absorption edges available in this spectral range. At the same time, EUV radiation has significantly larger penetration depths than electrons.
By combining a high photon-flux, table-top EUV source, structured EUV illumination in a scanning lensless imaging setup, and advanced computational Ptychography algorithms, an important breakthrough has recently been achieved by researchers at the HI-Jena.
A record-high spatial resolution of 16 nm has been demonstrated in combination with highly-accurate amplitude- and phase-imaging over wide fields of view [1]. In a first demonstration, the complex transmission of an integrated circuit (part of a solid-state disc) was precisely reconstructed as shown in fig. 1 a). By calculating the scattering quotient as the ratio of the observed phase shift and attenuation in each pixel, the nanoscale material composition is identified, as shown in fig. 1 b).
So far, high-performance lensless imaging at short wavelengths was restricted to large-scale facilities, where beam time is valuable and scarce. The presented experiments utilizing laser-generated coherent EUV radiation (high order harmonics) demonstrate that such capabilities get now available in compact table-top setups, which can be implemented in standard research laboratories but also in industrial or clinical environments.
Potential applications are found in materials and life sciences and many other areas. For example, high-resolution studies of the composition and the nano-structure of compound battery materials or the investigation of sub-cellular structural and chemical changes caused by diseases or infections get feasible. The highly-accessible setups will facilitate in-house, rapid-cycle, and fast-feedback studies without the need for travel and beam times and will thus speed up future developments in many fields.
Encouraging results have already been obtained when imaging microorganisms in the novel XUV microscope [2]. Two dried model specimens: germlings of a fungus (Aspergillus nidulans), and bacteria (Escherichia coli) cells have been investigated with a half-period spatial resolution of 58 nm. Again a scattering quotient micrograph uncovers the composition of the sample averaged along the propagation direction in each pixel of the image. In both investigated samples, different biological compositions (such as proteins, lipids, and hydrocarbons) have been obtained and successfully assigned to the internal functional units of the respective microorganisms. Example images for E. coli bacteria are shown in fig. 2. This first demonstration underlines the potential of imaging in the extreme ultraviolet spectral region and opens up new opportunities for life-science applications.
References:
[1] W. Eschen, L. Loetgering, V. Schuster, R. Klas, A. Kirsche, L. Berthold, M. Steinert, T. Pertsch, H. Gross, M. Krause, J. Limpert, and J. Rothhardt, "Material-specific high-resolution table-top extreme ultraviolet microscopy," Light Sci. Appl. 11, 117 (2022).
[2] C. Liu, W. Eschen, L. Loetgering, D. S. Molina, R. Klas, A. Iliou, M. Steinert, S. Herkersdorf, A. Kirsche, T. Pertsch, F. Hillmann, J. Limpert, and J. Rothhardt, "Visualizing the ultra-structure of microorganisms using table-top extreme ultraviolet imaging," PhotoniX 4, 1–15 (2023).
