Slicing and guiding of light waves by atomically thin materials

Light waves interacting with an optical medium are generally investigated in terms of transmission, reflection, and absorption by the material. However, when the propagation direction of light changes to be parallel and bisected by the material, the fundamental behavior of light-matter interaction becomes significantly distinct from that of the normal incidence. Here, we explored an extreme limit of this parallel configuration realized by using a monolayer MoS₂ film that is grown on fused silica substrate and then immersed inside index-matching liquid to isolate optical responses from atomically thin materials. With this system, we observed that a beam propagating along the film is sliced into two sub-beams leaving a nodal line at the film location, regardless of the photon energy, whether larger or smaller than the MoS₂ bandgap. In addition, by collecting field intensity elastically scattered from the film surface, we visualized intense light waves starting from the edge of film and then eventually dissipating while it propagates, which we identified as a guided wave by further evidence. Our results demonstrate that atomically thin materials slice and guide light waves, presenting an ideal platform to study optics and photonics in two-dimensional limit.