Optical cavities could provide new technologies


Image: How a researcher imagines a chemical reaction in an optical cavity.
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Photo credits: Illustration: Enrico Ronca, IPCF-CNR

A research team from the Norwegian University of Science and Technology (NTNU) is studying a topic called optical cavities and how the light trapped inside interacts with atoms, molecules and other particles. The technology could prove valuable for the development of energy-efficient chemical processes or drug synthesis, for example.

The work of Professor Henrik Koch and PhD students Rosario R. Riso, Tor S. Haugland and Marcus T. Lexander has shown amazing results and is gaining attention.

“We have observed an effective method for describing molecules in optical cavities,” says Professor Koch, who works both at NTNU’s Institute of Chemistry in the Faculty of Science and at the Scuola Normale Superiore di Pisa (SNS) in Italy.

Their results were recently published in Physical Check X and nature communication.

Optical cavities?

But what exactly are optical cavities? First, remember that at this scale, the world seems a little different than what most of us are used to.

In quantum mechanics, particles and waves are indistinguishable because they have a so-called wave-particle duality or a wave function.

Even in optical cavities, which exhibit a molecule-light duality, we cannot distinguish between particles and light. This coupling creates new colors and properties in the molecules that can be exploited in chemical and physical processes.

Reflective mirrors

Optical cavities can be created by using two mirrors that are extremely close together, typically nanometers apart. To understand molecules, one must look at the environment in which they are found.

All atoms and molecules, like the oxygen in the Northern Lights, emit light because they interact with the faint light that is always present in a vacuum or “empty” space. The special property in this case is that the light in an empty optical cavity is not the same as the light in the vacuum outside. When you place a molecule in the cavity, both the color and the intensity of the light emanating from the molecule change.

“In an optical cavity made of reflecting mirrors, molecules can interact strongly with the quantum mechanical vacuum,” says Koch.

The research team works exclusively with simulations, so it is important to work with an experimental group that can test whether the team’s theories are correct.

To this end, the research team is collaborating with Professor John de Mello and NTNU Nano PhD student Enkui Lian to produce prototypes for use in research.

A common theory

Molecular orbital theory is an important theoretical tool in chemistry and is widely used in both inorganic and organic chemistry to understand chemical reactions.

“We have found the first consistent molecular orbital theory for quantum electrodynamics – that is, a molecular orbital theory for molecules in optical cavities,” says Koch.

Using this theory, scientists can predict how molecules in optical cavities will react and what types of colors and properties the molecules will have.

€2.5 million in EU support

Just being able to change the properties of molecules is interesting enough for researchers, because new insights and insights are always exciting. But practical applications can’t hurt either, and this research has that potential.

Research into the processes in optical cavities is a new field in chemistry. Synthesis in the pharmaceutical industry could be one of its practical applications. It could also be important when using catalysts to start and sustain chemical reactions. Perhaps it will contribute to the development of extremely fast quantum computers based on a similar concept.

Are you more interested now? At least the EU was.

Koch and the QuantumLight project were awarded a €2.5 million grant by the European Research Council (ERC) last year for research into chemistry in optical cavities.

The academic group is currently working towards being nominated a Center of Excellence (SFF) by the Research Council of Norway. This designation would allow the research team to receive research funding for up to ten years and provide opportunities for larger and more exciting research projects.

Reference: Rosario R. Riso, Tor S. Haugland, Enrico Ronca & Henrik Koch. Molecular Orbital Theory in Cavity QED Environments. Published: March 15, 2022. nature communication Volume 13, item number: 1368 (2022). https://doi.org/10.1038/s41467-022-29003-2

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