APPLICATIONS OF TECHNOLOGY:
- Spectroscopy and microscopy
- Removes the standing wave structure from a ponderomotive phase plate
- Enables an easier and faster process of aligning the electron beam to the phase plate
- Ensures data of equally high quality for entire data collection period
- Tunable phase shift – between 0 and 360°
- Negligible electron loss
- Based on a continuous-wave system to be compatible with standard transmission electron microscopy (TEM) designs
Researchers at the Berkeley Lab led by Jeremy Axelrod have developed an invention that extends the capabilities of a previous ponderomotive phase plate technology; specifically, its spatial profile can now be controlled via the optical polarization state of the light used in such a laser phase plate. This phase plate consists of a focused standing light wave which phase shifts a through-going electron beam to implement Zernike phase contrast imaging in transmission electron microscopy (TEM).
The present invention allows the standing wave structure to be removed via a simple modification of the laser beam optics placed prior to the laser beam entering the optical cavity. This development enables the polarization of the light wave to be user-controlled. As a result, the amount of the standing wave structure present in the laser phase plate can be tuned from its maximum to zero. The tunability of the invention allows users to select how much standing wave they want to remain in the laser phase plate, which is a highly advantageous feature considering that the standing wave structure has both a beneficial effect (additional image contrast enhancement) as well as a detrimental effect (the presence of ghost images). Since the standing wave structure diffracts through-going particles, this technology can be used to control the amount of diffraction occurring in the phase plate. In the context of TEM, eliminating the electron diffraction effect may be desirable because it removes image artifacts due to the electron diffraction. To the researchers’ knowledge, such an application of the effect has not been previously published. For the same reason, it can also be used as a switchable electron beamsplitter. Additionally, the technology may aid in the switch between the two phase plate profiles (with and without standing wave) during normal data collection to more accurately reconstruct data about the sample.
Researchers performed what they believe to be the first ever experiment demonstrating the fact that the ponderomotive potential should have a polarization dependence for fast particles. This invention ultimately overcomes the limitations of competing technologies – none of which can remove the standing wave structure from a ponderomotive phase plate – by providing control over a phase plate’s spatial profile and therefore enabling more versatile and accurate TEM imaging of samples.
DEVELOPMENT STAGE: Proven principle
STATUS: Patent pending. Available for licensing or collaborative research.
SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:
Optical-Cavity Phase Plate for Controllable, Stable Phase Shift in TEM and Cryo-EM Applications 2017-080