Active steering of cathodoluminescence through a generalized Smith-Purcell effect

Area of Science:

• Optics and Photonics
• Materials Science
• Condensed Matter Physics

Background:

• Optical metasurfaces can manipulate electron near-fields to generate Smith-Purcell (SP) radiation.
• Existing methods are limited in controlling the higher-order SP emission.

Purpose of the Study:

• To introduce a generalized Smith-Purcell effect using finite periodic metasurfaces with tunable elements.
• To demonstrate the capability of steering electron-driven light emission through precise control of metasurface properties.

Main Methods:

• Theoretical modeling of generalized Smith-Purcell radiation from finite periodic arrays.
• Investigating metasurface elements with individually tunable polarizabilities.
• Exploring active tuning using doped graphene and phase-change materials, compared to passive plasmonic structures (gold, silver).

Main Results:

• Demonstrated higher-order SP radiation control by tuning metasurface element amplitude and phase.
• Established a theoretical framework for an SP steering device.
• Showcased tunable light sources spanning terahertz to visible frequencies.

Conclusions:

• Programmable electron-driven light sources and spectroscopic probes are achievable.
• Tunable metasurfaces represent a significant advancement for electron-photon technologies.