Abstract
We propose a Zernike phase contrast electron microscope that uses an intense laser focus to convert a phase image into a visible image. We present the relativistic quantum theory of the phase shift caused by the laser–electron interaction, study resonant cavities for enhancing the laser intensity and discuss applications in biology, soft-materials science and atomic and molecular physics.
Highlights
The resolution of modern transmission electron microscopes (TEMs) [1] can be more than 10 000 times that of light microscopes
The image is imprinted, on the phase of the electron’s wave function. In optical microscopes, such a phase image can be made visible by Zernike phase contrast microscopy [2]: the part of the light beam that has not been diffracted by the specimen is phase shifted by π/2 by a quarter-wave plate, converting phase modulation into visible amplitude modulation
Attempts have been made to use bi-prism electron holography to record the phase of the electron beam, but this approach has been largely abandoned because subtle charging effects in the specimen itself result in degraded temporal coherence in an off-axis hologram, whereas they have little effect on the in-line holography that is provided by Zernike phase-contrast imaging
Summary
The resolution of modern transmission electron microscopes (TEMs) [1] can be more than 10 000 times that of light microscopes. Attempts have been made to use bi-prism electron holography to record the phase of the electron beam, but this approach has been largely abandoned because subtle charging effects in the specimen itself result in degraded temporal coherence in an off-axis hologram, whereas they have little effect on the in-line holography that is provided by Zernike phase-contrast imaging. In view of these challenges, the phase shift that occurs when an electron passes through a beam of light [10] is here envisioned as an alternative way to achieve phase contrast. We will discuss applications in biological specimens and other soft-matter specimens and give an outlook on other potential applications
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