When light interacts with the free electrons in a metal under certain circumstances, it generates a density wave called plasmon that occurs at optical frequencies. Plasmons are waves of excited surface electrons rather than movement of actual particles that can travel at near the speed of light. Therefore, computer processors with this technology can operate at much faster speeds than current electronics. Bridging optical and regular electronic circuits in computers requires the ability to control the plasmons. The EU-funded project TRUEVIEW (Time-resolved ultrafast electron visualization of evanescent waves) significantly enhanced understanding of the evolution of evanescent electromagnetic fields in nanophotonic structures and the underlying light-matter interactions that are necessary for modern optoelectronics research. By using the photon-induced near-field electron microscopy (PINEM) technique, scientists were able to visualise and characterise photonic and plasmonic nanostructures in both space and time with nanometre and femtosecond resolution. This advanced technique exploits very short synchronised electron pulses to sense photo-induced ultrafast electromagnetic fields confined to nanoscale structures. In a carefully designed experiment where a plasmonic standing wave was excited by a photon on a nanoscale resonator, scientists captured an ultrafast snapshot of the confined light mapping its distribution in energy and space in two dimensions. The resulting image reveals the wave-properties of plasmons simultaneously with their quantum nature, in a single experiment. What's more, scientists captured a movie of propagating plasmonic waves in carefully designed propagating media. Propagation and interference were filmed through PINEM imaging using synchronised pulses of electrons at different time delays in a stroboscopic approach. In similar experiments, scientists demonstrated control of the plasmonic interference pattern through combination of the nano-patterning design and polarisation of the excitation light. TRUEVIEW successfully unravelled the working principles of nanoscale-confined optical waves and the manipulation of light in optoelectronic nanostructures. By using PINEM to visualise and characterise photonic and plasmonic nanostructures in both space and time, it also successfully established the field of ultrafast electron microscopy within the European research community.
Ultrafast processors, plasmons, wave-particle, TRUEVIEW, electron microscopy