Wavefront Shaping in the TEM: What Promise Does it Hold for Materials Characterisation?

Wavefront shaping or the ability to freely change the phase of a coherent wave is a powerful concept in diverse areas of science ranging e.g. from light optics, telecommunication, radar, acoustics and seismology. The ability to freely shape the wavefront of a coherent electron wave in transmission electron microscopy has become a recent possibility with our 48 pixel array of electrostatic phase shifters that cen be placed in an aperture position of a modern electron microscope. This changes the paradigm from attempting to make ever smaller probe sizes for spatial resolution to create a large basis set of orthogonal quantum states to interact with a sample. We discuss several potential applications of this new tool with proof of concept implementation and simulations. Such applications can include increased selectivity in probing EELS excitations based on symmetry selection, adaptive optics providing high contrast images while dynamically correcting aberrations and bringing out relevant (eg phase) contrast. It also helps for inverse problems in ptychography and diffraction problems where the phase control over the incoming beam can break point symmetry and make it easier for inverse algorithms to converge to a single solution.