A groundbreaking method for advancing discoveries in materials science has been proposed by scientists from the University of Ottawa and the Max Planck Institute for the Science of Light. This approach combines terahertz (THz) spectroscopy with real-time monitoring, enabling the unveiling of hidden properties of matter. Unlike other forms of radiation, terahertz waves have the capability to capture rapid changes in materials that are imperceptible to the naked eye. Remarkably, scientists can now employ terahertz waves to generate high-speed movies of hot electrons in silicon, recording up to 50,000 frames per second—a previously unparalleled feat.
Headed by Jean-Michel Ménard, an associate professor of physics at the University of Ottawa’s Faculty of Science, a team of researchers employed two innovative techniques: chirped-pulse encoding and photonic time-stretch. Through the first technique, the information carried by a THz pulse is encoded onto a chirped supercontinuum in the optical range, resembling a traveling rainbow. Subsequently, the second technique stretches the rainbow pulse within a lengthy fiber, effectively slowing down the rate of information transmission. This enables the real-time recording of the data using sophisticated electronic equipment. The process is reiterated using a series of pulses spaced 20 microseconds apart, which can be merged to create a movie depicting the low-energy dynamics occurring within a material.
Ménard explains the significance of their study, titled “Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz,” published in Nature Communications. He highlights their pioneering photonics system, which is capable of real-time measurement of low-energy dynamics with a time resolution nearing the microsecond range. Notably, their compact setup supplants the need for the previously exclusive use of large synchrotron facilities, thus expediting time-resolved THz spectroscopy—an influential technique for the analysis of diverse materials.
What’s next?
The utilization of this system in experiments will involve the examination of vibrational resonances of molecules, aiming to unravel the enigmatic role of enzymes in chemical reactions. Additionally, it will enable the observation of imperceptible changes within living organisms when subjected to sudden temperature increases.
Ménard emphasizes the applicability of their rapid THz photonic system in condensed matter experiments, specifically for the investigation of non-reversible electronic or lattice reconfigurations that occur during phase transitions. He anticipates that this breakthrough will be instrumental in uncovering a new realm of rapid and unpredictable processes, further enhancing the effectiveness of THz spectroscopy as a characterization tool in materials physics.
With the researchers’ photonic system, a groundbreaking opportunity arises to explore the behaviors of irreversible physical, chemical, and biological phenomena. This includes delving into the realm of electronic transport in semiconductors, investigating chemical exothermic reactions, and unraveling the intricate process of protein folding within biological systems. The hidden intricacies of swift and unpredictable dynamics are finally unveiled, forever transforming our comprehension of the world.
Source: University of Ottawa