Physicists have demonstrated that ultra-thin two-dimensional materials like tungsten diselenide can change the polarization of visible light by a few degrees at specific wavelengths when subjected to small magnetic fields. This is suitable for use on chips. German and Indian physicists have shown that ultra-thin two-dimensional materials such as tungsten diselenide can rotate the polarisation of visible light by several degrees at certain wavelengths under small magnetic fields suitable for use on chips. It has been known for centuries that light exhibits wave-like behaviour in certain situations.The ability of certain materials to change the direction of light wave oscillation is known as polarisation rotation. This property is important for optical communication networks, where it is used in a component called an “optical isolator” or “optical diode.” These components allow light to travel in one direction while preventing light from going in the opposite direction. A recent study by German and Indian physicists found that ultra-thin two-dimensional materials like tungsten diselenide can rotate the polarisation of visible light by a few degrees at specific wavelengths under small magnetic fields, making them suitable for use in optical communication networks.The University of Münster, Germany, and the Indian Institute of Science Education and Research (IISER) in Pune, India, have released their findings in the journal Nature Communications.
Traditional optical isolators are often quite large, ranging in size from several millimetres to several centimetres. This has made it difficult for researchers to develop miniaturised integrated optical systems on a chip that can compete with everyday silicon-based electronic technologies. Currently, integrated optical chips only contain a few hundred elements. To address this issue,The German-Indian team’s work is a significant advancement in the development of miniaturized optical isolators. The 2D materials they used are extremely thin, only a few atomic layers thick, making them a hundred thousand times thinner than a human hair. Prof Rudolf Bratschitsch from the University of Münster believes that in the future, these two-dimensional materials could be the key components of optical isolators, allowing for on-chip integration in current and future quantum optical computing and communication technologies. Prof Ashish Arora from IISER also highlights the potential of these materials in enabling on-chip integration for optical and quantum optical technologies.The researchers have discovered that atomically thin 2-D magnets could potentially replace bulky magnets used in optical isolators, leading to a significant reduction in the size of photonic integrated circuits. The team has also identified the mechanism behind this discovery, which involves bound electron-hole pairs, or excitons, in 2D semiconductors rotating the polarization of light when subjected to a small magnetic field. According to Ashish Arora, conducting experiments on such sensitive materials is challenging due to their small sample areas. Therefore, the scientists had to develop a new method for conducting their research.A new measurement technique has been developed that is approximately 1,000 times faster than previous methods. This breakthrough is detailed in a study published in Nature Communications by Benjamin Carey, Nils Kolja Wessling, Paul Steeger, Robert Schmidt, Steffen Michaelis de Vasconcellos, Rudolf Bratschitsch, and Ashish Arora. The study discusses the giant Faraday rotation in atomically thin semiconductors and provides a DOI link for further reference. (http://dx.doi.org/10.1038/s41467-024-47294-5)