Scientists have achieved efficient electron-beam modulation using integrated photonics – circuits that guide light on a chip. The experiments could lead to entirely new quantum measurement schemes in electron microscopy.
The transmission electron microscope (TEM) can image molecular structures at the atomic scale by using electrons instead of light, and has revolutionized materials science and structural biology. The past decade has seen a lot of interest in combining electron microscopy with optical excitations, trying, for example, to control and manipulate the electron beam by light. But a major challenge has been the rather weak interaction of propagating electrons with photons.
The researchers have successfully demonstrated extremely efficient electron beam modulation using integrated photonic microresonators. Photonic integrated circuits can guide light on a chip with ultra-low losses, and enhance optical fields using micro-ring resonators.
The technique enables a strong modulation of the electron beam, with only a few milli-Watts from a continuous wave laser – a power level generated by a common laser pointer. The approach constitutes a dramatic simplification and efficiency increase in the optical control of electron beams, which can be seamlessly implemented in a regular transmission electron microscope, and could make the scheme much more widely applicable.