Nonlinear optical properties of two-dimensional materials

Two-dimensional materials have broad potential application because of their unique structures and physical properties, and have made great progress in photonics, optoelectronics, electronics, and many other aspects. Recently, the application requirements of big data, optical networks, and micro-optical switches have directly or indirectly promoted research work on nonlinear optical properties of two-dimensional materials. In this paper, the research progress of nonlinear optical properties of two-dimensional materials (including single layer, few layers and suspension) is reviewed. Firstly, several common two-dimensional materials (graphene, transition metal chalcogenides, black phosphorus, etc.) and the basic theories of nonlinear optics are briefly introduced, and then different nonlinear optical effects (parametric processes including second harmonic, third harmonic and four-wave mixing; non-parametric processes including saturable absorption, two/multi-photon absorption and nonlinear refraction) of the two-dimensional materials are mainly stated, and the application prospects and probable research directions of these micro-nano materials in the field of nonlinear optics are forecasted in each part.