Scientists create the thinnest lens on Earth, enabled by excitons

https://phys.org/news/2024-05-scientists-thinnest-lens-earth-enabled.html

"3 atoms thick flat lens relying on quantum effects... single layer tungsten disulfide flat lens half mm wide, 0.6 nm thick... Fresnel lens has concentric WS2 rings with gaps in between, focusing using diffraction rather than refraction...  focusing efficiency relies on quantum effects within WS2 enabling efficient absorption/ re-emission of light at specific wavelengths... forms excitons, sensitive to charge density, enabling changing refractive index of the material by applying a voltage... AR glasses"