Direct visualization of electromagnetic wave dynamics by laser-free ultrafast electron microscopy

Femtosecond lasers can be integrated with electron microscopes to directly image transient structures and morphologies in materials in real time and space. In a new report, Xuewen Fu and a team of scientists in condensed matter physics, microsystems, nanotechnology and materials science in China and the U.S. developed a laser-free ultrafast electron microscope (UEM) offering similar potential but without the requisite femtosecond lasers or elaborate instrumental modifications. The team created picosecond electron pulses to probe dynamic events by chopping a continuous beam with a radiofrequency (RF)-driven pulser with a pulse repetition rate tunable from 100 MHz to 12 GHz. They studied gigahertz electromagnetic wave propagation dynamics as an application for the first time in this work and revealed the transient oscillating electromagnetic field on nanometer space and picosecond time scales with time-resolved polarization, amplitude and local field enhancement. The study showed the use of laser-free, ultrafast electron microscopy (UEM) in real-space visualization for multidisciplinary research—specifically in electrodynamic devices associated with information processing technology. The research work is now published in Science Advances.