Physicists from the University of Warsaw, in collaboration with teams from across Poland, have successfully trapped infrared light within a material layer just 40 nanometers thick. The breakthrough, detailed in the journal ACS Nano, uses a subwavelength grating made from molybdenum diselenide (MoSe2) to confine and amplify light at scales previously thought impossible.
Traditional silicon or gallium-based structures struggle to contain light at such reduced dimensions, often losing their reflective properties as they shrink. The research team overcame this by leveraging the unique refractive index of MoSe2. Light travels 4.5 times slower through this material than it does in a vacuum, allowing the grating to trap infrared waves in a volume significantly smaller than their own wavelength.
Advancing photonic performance
The ability to manipulate light at the nanoscale is essential for the future of computing. As electronic circuits approach their physical limits, photonics offers a faster, mass-free alternative to moving data. The team’s design acts as a high-efficiency trap, concentrating infrared light so intensely that it triggers a nonlinear optical effect known as third harmonic generation.
This process converts infrared light into visible blue light. Researchers observed that the grating intensified this conversion effect more than 1,500 times compared to a flat, unstructured layer of the same material.
To move beyond experimental limitations, the researchers utilized molecular beam epitaxy (MBE) to produce the MoSe2 films. Previous methods relied on manual exfoliation, which restricted samples to microscopic sizes. The MBE technique allowed the team to grow uniform, high-quality layers spanning several square inches.
This production method achieves an extreme aspect ratio. The resulting film is roughly one million times wider than it is thick, a scale that dwarfs the proportions of standard paper. By proving that these ultra-thin structures can be manufactured at a larger scale, the researchers have provided a new blueprint for integrating photonic components into practical, high-speed hardware.
