Innovation and Partnerships Office

Optical-Cavity Phase Plate for Controllable, Stable Phase Shift in TEM and Cryo-EM Applications 2017-080


  • Biological research using high resolution cryogenic electron microscopy (cryo-EM)
  • Hard-matter material characterization
  • Other forms of research using transmission electron microscopy (TEM)


  • Ensures data of equally high quality for entire data collection period
  • Equally useful for radiation-tolerant and radiation-sensitive specimens
  • Tunable phase shift – between zero and 360°
  • Negligible electron loss
  • Based on a continuous-wave system to be compatible with standard TEM designs


Berkeley Lab and University of California, Berkeley researchers led by Robert Glaeser and Holger Müller have advanced the utility of transmission electron microscopy (TEM) and cryogenic electron microscopy (cryo-EM) for determining macromolecular structure and the structure of novel materials. The team has developed an optical cavity phase plate that changes the phase of the transmitted wave relative to the scattered wave when an intense laser beam is focused on the back focal plane of a TEM objective lens.

The desired phase shift between scattered and unscattered electrons is produced by the standing wave pattern that builds up in the mildly focused optical beam within the cavity. The amount of phase shift of the electron wave does not change with the length of time that the phase plate is used, in contrast with devices that bring physical objects near to or into the electron beam. As a result, phase contrast remains at 100% the intended value throughout the data collection period, yielding data of consistently high quality.

Advances in TEM are transforming the fields of structural biology and materials science. However, TEM is limited for specimens consisting of lighter elements, such as biological molecules, which are nearly transparent to the electron beam and thus yield weak image contrast. TEM image quality has been improved with carbon foil-based phase plates. However, exposure to an electron beam changes the properties of the carbon foil over time, varying the contrast transfer function and limiting the time a phase plate can be used. By providing a controllable, stable phase shift, the Berkeley Lab optical cavity phase plate will allow the TEM and cryo-EM community to take full advantage of improved image contrast.

DEVELOPMENT STAGE: Proven principle of achieving the required laser intensity and long-term stability of a focused laser beam

STATUS: Patent pending. Available for licensing or collaborative research.

Schwartz, O., Axelrod, J., Haslinger, P., Ophus, C., Glaeser, R., and Müller, H. Continuous 40 CW/cm2 laser intensity in a near-concentric optical cavity, October 2016, arXiv:1610.08493


High Affinity Specimen Support Film for Electron Microscopy, 2015-002

Consistent, Reliable Preparation of Cry-EM Specimens, 2015-108