Light Source Aims to Build on Nobel Prize-winning Technology

A team at Heriot-Watt University, led by professor Christian Brahms, is developing a light source for extremely fast laser pulses that will enable scientists to observe some of the fastest processes in the natural world as they occur. The new laser light source will capture natural processes like light absorption in photosynthesis in attoseconds.

The project, which is called FASTER — short for Flexible Attosecond Soliton Transients for Extreme Resolution — will build on the EUV attosecond technology that received the Nobel Prize in Physics in 2023.

Brahms and his team will design and build a laser light source that mimics natural sunlight, but in extremely short flashes. “My aim is to create laser pulses with similar extremely short duration to conventional attosecond science sources, but at the same ultraviolet and visible wavelengths as we get from the sun,” he said.

FASTER will bring attosecond time resolution to ultrafast spectroscopy experiments in the UV, visible, and IR regions of the electromagnetic spectrum. This will enable scientists to study ultrafast dynamics entirely with non-ionizing radiation and without the need for strong-field excitation or probing.

A research team led by professor Christian Brahms is building a new type of light source for extremely fast laser pulses that will allow scientists to observe some natural processes as these processes unfold. Courtesy of Heriot-Watt University.

Ultrabroadband optical attosecond spectroscopy will be enabled by soliton self-compression. The researchers will create the optical attosecond pulses required for the new laser light source by building on the results of the recent High-energy soliton (HISOL) project.

HISOL combines the high damage threshold and far UV (FUV) transparency of gas media, the long interaction lengths enabled by waveguides, the guidance of high-energy laser pulses in large-core hollow capillary fibers, and the nonlinear evolution of ultrafast laser pulses in the higher-order-soliton regime. This combination allows IR laser pulses to be converted to wavelength-tunable FUV pulses with a few-femtosecond duration and near-perfect beam properties.

Using tailored soliton dynamics in hollow-core waveguides, the FASTER team will convert femtosecond pulses to attosecond pulses. The resulting attosecond pulses will be used on various samples to perform ultrabroadband optical attosecond pump probe and 2D spectroscopy experiments, starting with condensed-matter targets.

While current attosecond technology, including the 2023 Nobel Prize-winning breakthrough, can create extremely short pulses of light at UV or X-ray wavelengths, it is limited when it comes to natural phenomena, because natural processes involve sunlight, not the wavelengths used in laboratory experiments.

FASTER will allow scientists to take “freeze-frame” images of exceptionally fast microscopic processes in molecules and materials. “This will fill in attosecond technology’s blind spots and directly relate our knowledge of ultrafast processes to other areas, like photochemistry or materials science,” Brahms said.

“Many of the most important breakthroughs in the history of science have been enabled by observing nature at scales far beyond the limits of human perception,” he said. “That’s exactly what we’ll be working on — pushing far beyond the limits of conventional laser sources to bring fundamental science into focus.”

The FASTER project to achieve a very fast laser light source for natural phenomena will take place over a five-year period and is scheduled to officially begin in the summer of 2025. It is one of 50 research projects in the UK to receive the European Research Council’s (ERC’s) Starting Grant in 2024. Brahms and his team will receive £2.5 million ($3.3 million) in ERC funding.

ERC funding supports research in a range of fields. “The new ERC Starting Grants winners aim to deepen our understanding of the world,” Iliana Ivanova, European Commissioner for Innovation, Research, Culture, Education, and Youth, said. “Their creativity is vital to finding solutions to some of the most pressing societal challenges.”

“Empowering researchers early on in their careers is at the heart of the mission of the ERC,” Maria Leptin, ERC president, said.

Research on HISOL was published in APL Photonics (www.doi.org/10.1063/5.0206108).