All-2D material photonic devices.

Two-dimensional (2D) materials are extensively used in almost all scientific research areas, from fundamental research to applications. Initially, 2D materials were integrated with conventional non-2D materials having well-established manufacturing methods. Recently, the concept of constructing photonic devices exclusively from 2D materials has emerged. Various devices developed to date have been demonstrated based on monolithic or hetero 2D materials. In this review, photonic devices that solely consist of 2D materials are introduced, including photonic waveguides, lenses, and optical cavities. Exploring photonic devices that are made entirely of 2D materials could open interesting prospects as they enable the thinnest devices possible because of their extraordinarily high refractive index. In addition, unique characteristics of 2D materials, such as high optical anisotropy and spin orbit coupling, might provide intriguing applications.