Polymer-based tunable optical components allow for metasurfaces that can switched with light

A material coating, whose light refraction properties can be precisely switched between different states, has been developed by an interdisciplinary research team from the departments of chemistry and physics at the University of Jena. The team, led by Felix Schechter, Sarah Walden, Purushottam Paudel, and Isabel Stude, combined polymers that react to light with so-called metasurfaces.

This innovation has led to the creation of new optical components that can potentially be used. Signal processing. Their results Now published in the journal ACS Nano.

Combining two established systems to create something new

“Both metasurfaces and light-switchable polymers have been known in principle for decades,” explains Sarah Walden from the Institute of Solid State Physics, who now leads a research group in Australia. “But we are the first to combine the two in this form to develop new components for optical applications,” she adds.

Metasurfaces are nanostructured thin layers with characteristic structural sizes smaller than the wavelength of light. This allows the properties of light and its propagation to be specifically influenced, enabling a variety of optical functions that would otherwise be performed by lenses, polarizers, or gratings. Switchable polymers, on the other hand, are plastics whose properties—such as the refractive index of light—can change between different states.

“The polymers we used contain dye molecules,” says Felix Schechter of the Institute of Organic Chemistry and Macromolecular Chemistry. “This means that they absorb light of a certain wavelength and, in doing so, change their structure – and thus their properties, such as in this case the refractive index of light.”

To return the dye to its previous structure with the same properties, light of a different wavelength is required. Physicist Isabelle Stude explains, “What’s special about our system is that these changes Return index affects the optical properties of a metasurface when it is coated with such a a. Polymer“

The changes achieved were surprisingly significant, even compared to previously known similar systems. “Since the polymers show different absorption depending on the dye, the different effects can be very well separated from each other or combined,” summarizes the physicist.

Abnormal physical behavior

In addition to this promising result, the team made a surprising discovery. “In our work, we used two different dyes separately, each applied to the metasurface. This confirmed the effect,” Schechter explained. “However, additive effects occur when combining the two switchable polymers,” he reports. “We suspect the two are different. Color molecules communicate with each other, but we can’t say for sure at this point.” Further investigation is needed to elucidate this interesting behavior.

Although the primary focus with these switchable surfaces was to demonstrate the underlying principle, the research group can envision several applications. “Since these surfaces can switch between different property states with light, sensor technology is a natural application area,” the researchers say.

It is also conceivable that such switchable surfaces could be used for optical data processing. “Of course, it would make our team happy if these components could be used for optical neural networks, for example, that could process image information in the same way that electronic artificial intelligence can now. is,” says Schechter.

“However, because this type of data processing is based on light rather than electronics, it is significantly more energy efficient and faster than traditional computer-based AI.”