Multi-Focus Additive Metalens Based on Complex Coding Principle

The convolution addition principle of encoding metasurface based on traditional theories can only achieve angular deflection of a single beam. In this article, the encoding mode of the metasurface is extended to the complex domain, and the concept of complex encoding metalens is proposed, which can realize the joint control of the multi-focus and multi-angle in the metalens imaging space. Complex coding reveals the relationship between different bit codes, and the resulting coded metalens is closer to the nature of electromagnetic (EM) wave propagation in physical sense. Using the complex addition theorem to add two metalens with different encoding modes, the new metalens is extended to a higher bit, and has the angular characteristics of the previous two metalenses focal points. At this time, the angle regulation of the multi-focal point is mutually not disturbed. Our proposed complex additive encoding metalens method provides a new idea for the design of multi-focal lenses in the future.