In a major step toward the future of light-based technology, researchers at MIT have created incredibly small optical devices that can change how they interact with light—on demand.
These new tools are thinner, more powerful, and more flexible than anything we’ve seen before, thanks to a special material called chromium sulfide bromide (CrSBr).
The study, published in Nature Photonics, comes from MIT’s Computational Materials and Physics teams, led by Professor Riccardo Comin.
These scientists are exploring nanophotonics, which is the science of controlling light at the nanoscale—one billionth of a meter.
Nanophotonic devices are already used in everything from high-speed internet to medical imaging, but they’ve had some major limitations.
Until now, materials like silicon or titanium dioxide have been the go-to building blocks for nanophotonic tools.
These materials are reliable but come with two key problems. First, they don’t interact with light as strongly as scientists would like, which limits how small and efficient devices can be.
Second, once these materials are shaped into a device, you’re stuck with whatever optical behavior they’ve been built with. You can’t easily change how they handle light after the fact.
That’s where CrSBr changes the game. This unique material has a powerful response to light and can be manipulated with magnets—without any physical movement or heat.
It owes these special properties to “excitons,” which are pairs formed when light energizes electrons, leaving behind positively charged “holes.” These electron-hole pairs behave like particles and interact very strongly with light.
Using CrSBr, the MIT team was able to build photonic crystals that are not only much smaller—some just 6 nanometers thick—but also tunable. By applying a magnetic field, they could instantly change how light flows through the device. This dynamic control is something traditional materials simply can’t offer, and it opens the door to smarter, more adaptable technologies.
Even more exciting, this strong light-matter interaction in CrSBr creates hybrid particles called polaritons.
These are part light, part matter, and can do things that regular photons (light particles) can’t—like enhancing light signals or enabling advanced quantum behaviors. In most systems, polaritons only appear with special optical cavities, but CrSBr can produce them on its own.
Currently, these effects work at ultra-cold temperatures (around -222°F), which limits some everyday uses. But in areas like quantum computing, precision sensing, and advanced simulations, these cold environments are already standard. The MIT team is also looking at related materials that might work at room temperature in the future.
This breakthrough could eventually lead to better optical chips, reprogrammable light circuits, or even devices that mimic the brain using light instead of electricity.
In the world of optics, the ability to shape and reshape how light behaves—without moving parts or physical contact—is a big leap forward. CrSBr could be the material that makes it possible.
