A new detector will let scientists watch chemical reactions unfold in real time using terahertz light—a part of the spectrum that has been too slow to use for fast processes until now. Terahertz waves sit between infrared and microwaves, and they can reveal unique information about molecules. But existing thermal detectors are sluggish and easily swamped by background noise, making them useless for studying rapid events like chemical reactions or photochemistry. This project combines a fast TeraFET detector with a multi-pass optical cavity that boosts sensitivity roughly 100-fold, then adds an ultraviolet laser to trigger reactions and analyse them on sub-microsecond timescales. If it works, the system could transform how researchers study fast chemical dynamics—from atmospheric chemistry to industrial catalysis. It may also open the door to practical terahertz sensing outside specialist labs, for example in security scanning, biomedical imaging, or industrial quality control. The work is primarily fundamental science, developing a new capability in spectroscopy. But past advances in terahertz technology have led to unexpected applications in airport security scanners and pharmaceutical quality testing, so the payoff could be broad.
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This project will develop fast detection systems to provide the first real-time gas sensing in the terahertz (THz) band of the electromagnetic spectrum. The THz band lies between the infrared and microwave regions and represents a meeting between electronic and optical technologies. Although numerous potential applications for THz sensing exist, including atmospheric and space research, security and biomedical imaging, and industrial inspection, there has been limited practical use of THz systems outside specialised laboratories. One key reason for this is the reliance on relatively slow thermal detectors to measure and analyse THz signals. These are inadequate for studying rapidly changing systems, such as chemical reactions. They are also highly susceptible to background thermal noise, which limits the accuracy and dynamic range of measurements. In this project, the student will develop new high-speed THz gas-sensing techniques, taking advantage of recent developments in fast THz detector technology. They will initially demonstrate THz spectroscopy using a multi-pass optical cavity, enabling THz waves to pass many times through gases, improving sensitivity by a factor of ~100. They will integrate a fast, and sensitive TeraFET detector into this system, in collaboration with Goethe University Frankfurt, to detect and analyse rapidly changing chemical concentrations for the first time. They will then integrate an ultraviolet laser or flashlamp into the system to "trigger" photochemical reactions, and analyse the reaction processes on sub-microsecond timescales.
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