Publishing their results in Nature Nanotechnology under the paper title “Transition metal dichalcogenide nanodisks as high-index dielectric Mie nanoresonators”, the researchers fabricated nanodisks from exfoliated multilayer tungsten disulphide (WS2) and demonstrated distinct Mie resonances and anapole states, which they could tune in wavelength over the visible and near-infrared range by varying the nanodisk size and aspect ratio. They also describe a novel regime of light–matter interaction, anapole-exciton polaritons occurring within a single WS2 nanodisk, which they say could be harnessed to design tiny optical resonators for light-based feedback loops.
“We have created a hybrid consisting of equal parts of light and matter. The concept opens completely new doors in both fundamental research and applied nanophotonics and there is a great deal of scientific interest in this,” explained Ruggero Verre, a researcher in the Department of Physics at Chalmers and one of the authors of the scientific article.
The discovery came about when Verre and his departmental colleagues Timur Shegai, Denis Baranov, Battulga Munkhbat and Mikael Käll combined two different concepts in an innovative way. Mikael Käll’s research team is working on what are known as nanoantennas, which can capture and amplify light in the most efficient way. Timur Shegai’s team is conducting research into a certain type of atomically thin two-dimensional materials known as transition metal dichalcogenides (TMDCs), which resembles graphene. It was by combining the antenna concept with stacked two-dimensional material that the new possibilities were created.
By creating a tiny resonance box with WS2, they were able to make the light and matter interact inside it, ensuring that the light is captured and bounces round in a certain ‘tone’ inside the material, efficiently transferring the light energy to the electrons of the TMDC material and back again.
The anapole-exciton polaritons light-matter interaction is akin to having the light energy oscillates between two states – light waves and matter – while it is captured and amplified inside the box. The researchers have succeeded in combining light and matter extremely efficiently in a single particle with a diameter of only 100 nanometres.
“We have succeeded in demonstrating that stacked atomically thin materials can be nanostructured into tiny optical resonators, which is of great interest for photonics applications. Since this is a new way of using the material, we are calling this ‘TMDC nanophotonics’. I am certain that this research field has a bright future,” says Timur Shegai, Associate Professor in the Department of Physics at Chalmers and one of the authors of the article.
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