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arXiv · 2305.03005

Attosecond electron microscopy by free-electron homodyne detection

John H. Gaida·Hugo Lourenço-Martins·Murat Sivis·Thomas Rittmann·Armin Feist·F. Javier García de Abajo·Claus Ropers
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Abstract

Time-resolved electron microscopy aims at tracking nanoscale excitations and dynamic states of matter with a temporal resolution ultimately reaching the attosecond regime. Periodically time-varying fields in an illuminated specimen cause free-electron inelastic scattering, which enables the spectroscopic imaging of near-field intensities. However, access to the evolution of nanoscale fields and structures within the light cycle requires a sensitivity to the optical phase. Here, we introduce Free-Electron Homodyne Detection (FREHD) as a universally applicable approach to electron microscopy of phase-resolved optical responses at high spatiotemporal resolution. In this scheme, a phase-controlled reference interaction serves as the local oscillator to extract arbitrary sample-induced modulations of a free-electron wave function. We demonstrate this principle through the phase-resolved imaging of plasmonic fields with few-nanometer spatial and sub-cycle temporal resolutions. Due to its sensitivity to both phase- and amplitude-modulated electron beams, FREHD measurements will be able to detect and amplify weak signals stemming from a wide variety of microscopic origins, including linear and nonlinear optical polarizations, atomic and molecular resonances and attosecond-modulated structure factors.

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John H. Gaida, Hugo Lourenço-Martins, Murat Sivis, Thomas Rittmann, Armin Feist, F. Javier García de Abajo, Claus Ropers. 2023-05-04. Attosecond electron microscopy by free-electron homodyne detection. https://doi.org/10.1038/s41566-024-01380-8

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