A breakthrough approach that will facilitate discoveries in materials science

Unveiling the invisible.

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We may observe minute details of the mechanical dynamics of complicated processes in slow motion. These movies can track low-energy resonances and reveal quick structural or chemical transformations if the visuals in each frame are swapped out for terahertz (THz) waves.

A new study in which scientists present a novel photonics system that can measure in real-time the low-energy dynamics of complex physical phenomena with a time resolution approaching the microsecond.

A group of researchers, led by Jean-Michel Ménard, an associate professor of physics at the Faculty of Science at the University of Ottawa, applied the chirped-pulse encoding and photonic time-stretch methods.

a novel photonics system
Credit: University of Ottawa

In the first method, a chirped supercontinuum in the optical region—which resembles a traveling rainbow—is imprinted with the information delivered by a THz pulse. The second slow down the pace of information so that it can be captured in real-time by sophisticated electronic apparatus stretching the rainbow pulse in time inside a long fiber. To create a video of the low-energy dynamics inside a material, these stages are repeated using a train of pulses spaced 20 microseconds apart.

Ménard said, “Our setup is distinctive: it is a compact system that replaces a technology that was only accessible in large synchrotron facilities and can quickly perform time-resolved THz spectroscopy, a powerful technique to analyze various materials.”

The system will be used in experiments that follow the vibrational resonances of molecules to investigate the puzzling function of enzymes in chemical reactions and track subtle changes in living things in response to rapid temperature increases.

Ménard said, “In condensed matter experiments, our rapid THz photonic system will observe a range of non-reversible electronic or lattice reconfigurations, notably occurring during phase transitions. We anticipate that (this) will play a crucial role in revealing a new range of fast and non-reproducible processes rendering THz spectroscopy an even more efficient characterization tool to make impactful discoveries in materials physics.”

For the first time, researchers may examine the behaviors of irreversible physical, chemical, and biological events, such as electronic transport in semiconductors, exothermic chemical reactions, and protein folding in biological systems, thanks to their photonic technology. Exposing the secret dance of rapid and surprising dynamics permanently changes how we perceive the world.

Journal Reference:

  1. Couture, N., Cui, W., Lippl, M. et al. Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz. Nat Commun 14, 2595 (2023). DOI: 10.1038/s41467-023-38354-3
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