Invited: LASER-ASSISTED ELECTRON MICROSCOPY: THE LASER PHASE PLATE AND BEYOND

Although transmission electron microscopy (TEM) is a mature field, the toolbox of electron optics is much more limited than the diverse and versatile machinery of light optics. Free-space coherent electron manipulation with lasers brings the atomic physics toolkit to the aid of electron microscopy. Laser-based spatial and temporal control of electron waves can provide a powerful new platform for realizing new imaging modalities in electron microscopy.

The recently demonstrated laser phase plate for Zernike phase contrast in TEM enhances images of light-element specimens, such as biological macromolecules or cell lamellae in cryo-electron microscopy or soft matter samples. The enhanced low-spatial-frequency contrast it provides can be particularly helpful in cryo-electron tomography. The laser phase plate also allows for a variable phase shift between the local oscillator and the scattered wave, which potentially enables holographic reconstruction of the exit wavefront.

We envision further advances in laser-based electron optics that will eliminate the throughput bottleneck in high-volume cryo-EM data collection by drastically reducing the number of background electrons; enable wide-field high-resolution imaging without an aberration corrector; and, in a longer time frame, allow for quantum-enhanced imaging with a signal-to-noise ratio defeating the shot noise limit.

I will discuss recent progress in the development of the laser phase plate and will provide an early view of further research into laser-assisted electron microscopy.