Compact Quasiparticle Light Source Could Rival FELs' Brightness

An international team of scientists is rethinking the principles of radiation physics, with the goal of creating super-bright light sources that are compact and relatively convenient to use.

Coherent light sources such as free-electron lasers (FELs) provide super-bright beams for studying biological, chemical, and physical phenomena. Although these super-bright sources can enhance the imaging for many applications from drug development to chip-making, their massive size and scarcity make them impractical for most laboratories, hospitals, and businesses.

Researchers from the University of Rochester, UCLA, the Instituto Superior Técnico (IST) in Portugal, and the Applied Optics Laboratory in France are working to enable broader access to super-bright light sources. The team is exploring new configurations that could provide radiance as powerful as the most advanced sources available today, within a much smaller footprint.

A team of scientists ran advanced computer simulations on supercomputers to propose a way to use quasiparticles for super-bright light sources. Courtesy of Bernardo Malaca.

The researchers introduced a concept for a quasiparticle-based light source that exploits the coordinated motion of an ensemble of light-emitting particles to achieve super-bright light. The quasiparticle light source relies on the collective and macroscopic motion of this ensemble of light-emitting charges, and it evolves and radiates in ways that is contrary to the physical laws for single charges.

Quasiparticles are formed by many electrons moving in sync. They can travel at any speed and withstand intense forces, even the forces near a black hole. A quasiparticle light source has the potential to produce very bright light that has just a small distance to travel.

“The most fascinating aspect of quasiparticles is their ability to move in ways that would be disallowed by the laws of physics governing individual particles,” professor John Palastro said.

The use of quasiparticles could allow for temporal coherence and super-radiance in plasma accelerators, enabling the accelerators to provide light that is comparable in brightness to FELs.

Palastro and his colleagues studied the properties of quasiparticles in plasmas by running advanced computer simulations on supercomputers available through the European High-Performance Computing Joint Undertaking. They found that quasiparticles can exhibit collective behavior that allows the quasiparticle to travel faster than the speed of light, although no individual particle can move faster than light.

Key to the application of a quasiparticle light source is the ability to control the quasiparticle’s trajectory, velocity, and acceleration, all of which can be extreme.

“The flexibility is enormous,” researcher Bernardo Malaca said. “Even though each electron is performing relatively simple movements, the total radiation from all the electrons can mimic that of a particle moving faster than light or an oscillating particle, even though there isn’t a single electron locally that’s faster than light or an oscillating electron.”

The researchers believe that quasiparticle radiation could enable a new class of super-bright light sources. The concept they propose has the potential to support new configurations of plasma-based accelerators for super-bright light that can provide radiation with clear experimental signatures spanning several wavelengths, from the terahertz to the extreme ultraviolet.

To obtain the brightness of free-electron lasers, plasma-based accelerators must become temporally coherent and super-radiant. These are the essential missing ingredients needed to create compact, affordable, plasma-based accelerator light sources that can be used in place of the current handful of FEL light sources available worldwide. Access to compact, bright sources based on quasiparticles could be transformative for research institutions, universities, hospitals, and industrial laboratories.

The researchers envision many potential applications for quasiparticle-based light sources that include imaging to scan for viruses and to investigate biological processes such as photosynthesis, improve computer chip manufacturing, and explore the behavior of the ordinary matter that makes up planets and stars. The simplicity of the quasiparticle approach makes it suitable for experimental demonstrations at existing laser and accelerator facilities.

The research was published in Nature Photonics (www.doi.org/10.1038/s41566-023-01311-z).