Speaker
Description
Accurate modelling of coherent electron wave propagation is essential for understanding and designing modern electron-optical systems, particularly in experiments involving structured beams and electron–photon interactions. However, numerical wave-optical simulations in electron microscopy face severe computational challenges due to the extremely short electron wavelength and the large convergence angles commonly used in modern instruments. In conventional implementations of the angular spectrum method (ASM), these conditions impose extreme spatial sampling requirements, often leading to computational grids that exceed practical limits of memory and computation time.
Here we introduce two numerical approaches that substantially relax these limitations: the scaling angular spectrum method and the no-lensing angular spectrum method. The scaling approach replaces the original optical system with a scaled equivalent in which lens-induced beam convergence is reduced, thereby relaxing sampling requirements while preserving the underlying wave-propagation physics. The no-lensing approach further simplifies propagation by suppressing the lensing contribution, enabling efficient simulations in regions away from focal planes. Together with the Bluestein (chirp-z) transform, these methods form a complementary toolbox for simulating complex electron-optical systems.
We demonstrate that these approaches reduce computational requirements by several orders of magnitude, enabling full wave-optical simulations of high-angle electron beams that were previously computationally infeasible. The presented framework opens practical pathways for routine wave-based modelling of electron beam propagation through complex optical systems and may facilitate the design of advanced beam-shaping elements and experiments involving coherent electron–photon interactions.