Anomalous reflection and directional excitation of SPPs based on element additive metasurface

The efficient combination of multiple functions through a single, planar and compact metastructure has become an emerging research area, offering the possibility to design and realize highly integrated and miniaturized multifunctional devices in photonics, but Huge challenges still need to be solved, especially in the visible wavelengths. Here, we design the metasurface structure by means of unit structure addition, allowing the linear polarization to be effectively separated into x-polarized and y-polarized components at normal incidence, and achieve anomalous reflection of light waves and unidirectional excitation of Surface Plasmon Polaritons (SPPs). The structure can locally propagate the energy of SPPs more efficiently, or reflect more energy out through the phase gradient. When linearly polarized light of 1200 nm is incident vertically, two different linear phase gradients are generated along the same direction, resulting in the realization of the same metasurface distinctly different functions. Among them, by analyzing the local electric field distribution caused by the interaction between the incident light and the structure, it can be clearly found that the x-polarized light effectively excites surface plasmons (SPPs), and most of the energy propagates to the right along the surface of the structure. The y-polarized light achieves an abnormal reflection of 30°, and it is verified that the large-angle deflection characteristic of 20°-60° can be achieved in the wavelength range of 1000nm-1500nm. The bifunctional metasurface developed in this study can provide ideas and methods for the study of photonic integrated devices in the optical band.