A group of researchers created functional metalenses that are one-tenth to one-half the thickness of the light wavelengths on which they focus. Metalenses made of layered 2D materials are as thin as 190 nm across.
It is the first time researchers have demonstrated that metalens can be made from 2D materials. The design principles can be applied to developing metalenses with more complex, tunable properties.
The researchers created functional metalenses one-tenth to one-half the wavelength, far exceeding the theoretical limit. First, they built metalens out of sheets of layered 2D materials, using well-studied 2D materials like hexagonal boron nitride and molybdenum disulfide.
A single atomic layer of these materials produces a small phase shift that makes efficient lensing impossible. As a result, the team used multiple layers to increase the thickness, but the thickness remained too small to achieve a full two-pi phase shift.
The researchers used mathematical models developed originally for liquid-crystal optics. These, combined with the metalens structural elements, enabled the researchers to achieve high efficiency even when the entire phase shift was not covered. Aside from achieving a new approach to metalens design at record-thinness levels, the team claims this work shows the promise of creating new imaging and optics devices entirely out of 2D materials.