Studying molecules at the nanoscale using light scattering

(17-02-2022) In his PhD, Kristof Reynkens examines how molecules can be studied at the nanolevel via Raman spectroscopy, allowing the technique to be used outside a lab environment.

Raman spectroscopy is very popular because it provides detailed information about the properties of atoms and molecules of a substance. Through Raman spectroscopy, one studies/measures the vibrations of atoms and molecules in a system when a laser is pointed at them, i.e. in a non-invasive manner.

This form of spectroscopy is based on inelastic scattering or Raman scattering of monochromatic light (one wavelength, e.g., a laser). This inelastic scattering is a physical effect in which the light undergoes an energy shift during scattering. This effect is called the Raman effect. The technique was named after the Indian scientist Sir Chandrasekhara Venkata Raman. He discovered the effect in 1928 and won the Nobel Prize in Physics for it in 1930. It was only after the development of the laser that Raman spectroscopy became popular.

"Raman spectroscopy, despite its many qualities, is still mainly limited to a lab environment because it requires bulky and expensive equipment (lasers, detectors and microscopes) to make the light scattering process clearly visible. Because of this, there has recently been a great interest in reducing the size of the spectroscopic system so that it can be integrated on an optical chip of a few millimeters in size. This makes it cheaper, more compact and therefore suitable for mass production," Kristof explains.

"However, there are also two problems that need to be solved. On the one hand, the amplification of the on-chip Raman signal is not sufficient, so one still has to use deep-cooled detectors and these are difficult to integrate on a chip. And on the other hand, an unwanted photonic background is generated in the core of the waveguides on the chip, which disturbs the detection"

"In my PhD, I have shown that the unwanted photonic background can be greatly reduced and furthermore I showed the way to further enhance the Raman signal in the future so that deep-cooled detectors are no longer needed. This brings the use of Raman spectroscopy outside the lab environment a big step closer," Kristof concludes.

Read the entire PhD

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PhD Title: On-Chip Raman Spectroscopy: Background Challenges and Their Mitigation

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Contact: Kristof Reynkens, Roel Baets, Stéphane Clemmen 

Kristof Reynkens

Kristof Reynkens was born on 9 March 1992 in Hasselt. He obtained a bachelor ‘s degree in engineering science at the KU-Leuven in 2014. Afterwards he obtained a master’s degree in nanosciences, nanotechnolgies and engineering at the KU-Leuven in 2016.

From 2016 to2021, he worked on his PhD thesis in the photonics research group at the Universiteit of Ghent under the supervision of Roel Baets and Stéphane Clemmen. His thesis work is devoted to inelastic scattering spectroscopy (both Raman and Brillouin) which is enabled by photonics integrated circuits. The results obtained during the thesis provide improvements that allow for a more feasible integration of Raman sensors with their instrumentation (laser, spectrometers, filters). His work resulted in two A1 publications in peer-reviewed journals.

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Editor: Jeroen Ongenae - Final editing: Ilse Vercruysse - Illustrator: Roger Van Hecke