Unveiling the invisible: A breakthrough in spectroscopy to enable breakthroughs in materials physics

By | June 12, 2023

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Single-pulse THz sensing pattern. Credit: Nature communications (2023). DOI: 10.1038/s41467-023-38354-3

Scientists from the University of Ottawa and the Max Planck Institute for the Science of Light are proposing a revolutionary approach that will facilitate breakthroughs in materials science by combining terahertz (THz) spectroscopy and real-time monitoring.

Terahertz waves are electromagnetic waves that can reveal hidden secrets of matter. They can capture rapid changes in materials invisible to other types of radiation. Scientists can now use terahertz waves to record real-time footage of hot electrons in silicon at 50,000 frames per second faster than ever before.

Led by Jean-Michel Mnard, an associate professor of physics at the University of Ottawa’s Faculty of Science, a team of scientists used two techniques, chirped-pulse coding and photonic time-stretch.

The study, “Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a frequency of 50kHz,” was published in Nature communications.

The first technique imprints the information carried by a THz pulse onto a chirped supercontinuum in the optical region, which resembles a traveling rainbow. The second stretches the rainbow pulse over time within a long fiber, slowing the rate of information so it can be recorded in real time by advanced electronic equipment. These steps are repeated using a train of pulses at 20 microsecond intervals, which can be combined to make a movie of the low-energy dynamics within a material.

“In this study, we present a new photonic system capable of measuring the real-time low-energy dynamics of complex physical phenomena with a time resolution approaching the microsecond. Our configuration is distinctive: it is a compact system that replaces a that was only accessible in large synchrotron facilities and can rapidly perform time-resolved THz spectroscopy, a powerful technique for analyzing various materials,” Mnard says.

What’s next?

Experiments based on this system will trace the vibrational resonances of molecules to study the enigmatic role of enzymes in chemical reactions and observe invisible changes in living organisms when exposed to a sudden increase in temperature.

“In the condensed matter experiments, our THz fast photonic system will be used to observe a series of non-reversible electronic or lattice reconfigurations, particularly occurring during phase transitions,” says Mnard. ‘We predict that it will play a crucial role in revealing a new range of fast and non-reproducible processes, making THz spectroscopy an even more efficient characterization tool for making impactful discoveries in materials physics.’

The researchers’ photonic system allows them for the first time to study the behaviors of irreversible physical, chemical and biological phenomena, including electron transport in semiconductors, exothermic chemical reactions and protein folding in biological systems. It is uncovering the hidden dance of rapid and unpredictable dynamics, forever altering our understanding of the world.

More information:
Nicolas Couture et al, Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz, Nature communications (2023). DOI: 10.1038/s41467-023-38354-3

About the magazine:
Nature communications

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