Nanophotonics focuses on controlling how light moves through tiny structures. Usually, these structures have fixed optical properties set during manufacturing. But quantum materials, because of their complex internal behaviors, could allow us to adjust how light behaves in these devices without changing their physical design.
In a leap toward smarter, smaller light-controlling tech, MIT scientists have developed a new nanophotonics platform that bends the rules of modern optics. By manipulating light at the scale of billionths of a meter, they’ve created ultracompact optical devices that are not only tiny and energy-efficient but also flexible, able to switch between different light modes on demand.
This kind of dynamic tunability has long been a missing piece in nanophotonics. Now, thanks to clever engineering and quantum materials, it’s becoming a reality.
This breakthrough brings us closer to a future where light-based devices are not just tiny and mighty, but also smart. Imagine optical components that can reprogram themselves on the fly, adapting to changes in their environment without needing to be rebuilt.
The nanophotonics orchestra presents: Twisting to the light of nanoparticles
That’s the promise of combining quantum materials, which have rich and tunable properties, with the precision of nanophotonics, the science of sculpting light at the nanoscale.
Nanophotonics primarily utilizes materials such as silicon to construct tiny structures that control light. These materials work well but have two significant limits: they don’t bend light very strongly, and once the device is made, its behavior can’t be changed without rebuilding it. Tunability is the secret sauce behind tomorrow’s photonics. It enables devices to adapt in real time, altering their imaging, sensing, light emission, and even learning capabilities, much like neural networks composed of photons.
Chromium sulfide bromide (CrSBr) is a quantum material that solves key problems in nanophotonics. It interacts strongly with light thanks to excitons, tiny light-sensitive particles, and responds to magnetic fields, making it easy to control. Its high refractive index lets scientists build ultra-thin optical structures, far slimmer than those made with traditional materials.
MIT researchers showed that by applying a small magnetic field, they could smoothly and reversibly change how light moves through CrSBr, without needing moving parts or temperature changes. This works because CrSBr’s refractive index shifts dramatically under magnetism, far more than in typical materials.
Electronics at the speed of light
CrSBr also creates polaritons, hybrid particles made of light and matter, that unlock new behaviors like stronger light interactions and quantum-level control. Unlike other systems, CrSBr does this naturally, without needing bulky optical cavities.
Even better, CrSBr can be added to existing photonic circuits, making it a practical tool for building smarter, tunable optical devices.
MIT’s results with CrSBr were achieved at very cold temperatures, around 132 kelvins. While that’s below room temperature, the material’s exceptional tunability makes it ideal for advanced applications like quantum simulation and reconfigurable light systems, where cryogenic setups are acceptable. According to researchers, CrSBr is so special that the cold is worth it. Still, the team is looking into similar materials that work at warmer, more practical temperatures.
Journal Reference
- Demir, A.K., Nessi, L., Vaidya, S. et al. Tunable nanophotonic devices and cavities based on a two-dimensional magnet. Nat. Photon. (2025). DOI: 10.1038/s41566-025-01712-2