Extreme Ultraviolet Ptychographic Microscopy

This project “Extreme ultraviolet ptychographic microscopy” (XUVPM) aims at improving the robustness and resolution of multispectral extreme ultraviolet (XUV) ptychography by realizing novel types of high divergence structured illumination in XUV spectral range.

In this microscope, two-color generation of high-order harmonics from an industrial grade femtosecond laser will be employed to create structured illumination with controllable degree of orbital angular momentum (OAM) to be combined with ptychography.

The high-repetition rate and high-average power femtosecond laser source will be temporally compressed with pulse post-compression and then split into two beams, the weaker beam is used to generate the second harmonic in a nonlinear crystal.

This forms a two-color interferometer where each arm contains a spatial light modulator (SLM) to individually imprint OAM into each beam.

Both beams are directed and focused into a noble gas jet in a non-collinear scheme to obtain high-order harmonics with controllable OAM.

The OAM-HHG beam consisting of multiple harmonic orders is focused onto the sample by two toroidal mirrors in Wolter configuration. The sample is scanned transversely and at each scan position a CCD camera records the diffraction pattern.

The generated XUV radiation will be optimized for its divergence and spatial properties, where the OAM can be controlled by the settings of the individual SLMs for the two generating colors.The fundamental research on the described illumination technique will offer a chance to investigate the resolution limit of tabletop XUV microscopy, which further can address imaging science challenges associated with, e.g., the fabrication, synthesis, and integration of next-generation quantum and semiconductor devices.

The work is supported by two experienced supervisors from complementary fields, covering the whole spectrum of the proposed project.