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Non-reciprocal phenomena generated by optical nonlinear effects without the requirement of external bias have important applications in modern photonics. In this paper, an optical nonlinear metasurface based on monolayer graphene integrated silicon resonant gratings is proposed. It is numerically confirmed that this type of metasurface can excite high-Q guided mode resonances in the communication band with normal incidence. Significant optical Kerr effect is achieved in the metasurface through high third-order polarization coefficient of graphene, and by changing the width and depth of the grating, the nonlinear effect of the metasurface can be effectively controlled to realize the application under different illumination conditions. In addition, remarkable non-reciprocity phenomenon is realized at an incident intensity of 0.085 G W / m 2. As an example, with a forward transmittance of 0.732 and a backward transmittance of 0.025, an optical diode is implemented at 1549.1 n m. Image 1 [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) are attracting more and more attentions as enabling materials for tunable nanophotonics. They can be processed into functional photonic devices through customized laser writing, providing great flexibility for fabrication and reconfiguration. Lithium Niobate (LN) has excellent nonlinear and electro-optical properties, but is difficult to process, which limits its application in nanophotonic devices. In this paper, we combine the emerging low-loss phase change material Sb 2 S 3 with LN and propose a new type of high Q resonant metasurface. Simulation results show that the Sb 2 S 3 -LN metasurface has extremely narrow linewidth of 0.096 nm and high quality (Q) factor of 15,964. With LN as the waveguide layer, strong nonlinear properties are observed in the hybrid metasurface, which can be employed for optical switches and isolators. By adding a pair of Au electrodes on both sides of the LN, we can realize dynamic electro-optical control of the resonant metasurface. The ultra-low loss of Sb 2 S 3 , and its combination with LN, makes it possible to realize a new family of high Q resonant metasurfaces for actively tunable nanophotonic devices with widespread applications including optical switching, light modulation, dynamic beam steering, optical phased array and so on. [ABSTRACT FROM AUTHOR]