Dual-channel infrared holographic metasurface based on composite phase modulation

Metasurface provide a new method to manipulate electromagnetic wave. The geometric phase obtained through rotating meta-atoms is widely used in broadband phase modulation technology. Although utilizing geometric phase modulation of metasurfaces enables flexible control over the response of electromagnetic waves, that is, by constructing specific phase distributions, desired electromagnetic functionalities can be achieved, along with the design of requisite electromagnetic devices. However, due to the inherent spin-locking nature of geometric phases, relying solely on a single-phase modulation method is increasingly unable to meet the application requirements for the integration, miniaturization, and intelligentization of electromagnetic devices. To address the aforementioned challenge, in order to break the spin-locking characteristic of geometric phase, we have realized decoupled design for orthogonal circularly polarized waves based on the composite modulation concept of geometric phase and transmission phase. We designed eight meta-atoms composed of silicon pillars and a substrate. for infrared wavelengths, with adjacent meta-atoms having fixed phase gradient of π/4. Meanwhile, the geometric phase of each meta-atom can cover the range of 0~2π. Subsequently, taking the holography as examples, the decoupled design of orthogonally circularly polarized waves is achieved, and the simulation results verify the feasibility of the aforementioned spin-decoupled regulation mechanism. In conclusion, the above metasurface exhibits excellent ability to regulate electromagnetic waves in the infrared spectrum. This research has potential application prospects in the fields of infrared communication, imaging, and others.