High-resolution wavefront sensing and aberration analysis of multi-spectral extreme ultraviolet beams

Coherent multi-spectral extreme ultraviolet beams have great potential for providing high spatial and temporal resolution for microscopy and spectroscopy applications. But due to the limitations of short-wavelength optics and the broad bandwidth, it remains a challenge to perform quantitative, high-resolution beam characterization. Here we present a wavefront sensing solution based on multiplexed ptychography, with which we show spectrally resolved, high-resolution beam reconstructions. Furthermore, using these high-fidelity quantitative wavefront measurements, we investigate aberration transfer mechanisms in the high-harmonic-generation process, where we present and explain harmonic-order-dependent astigmatism inheritance from the fundamental wavefront. This ptychographic wavefront sensing concept thus enables detailed studies of the high-harmonic-generation process, such as spatiotemporal effects in attosecond pulse formation.