Dual-state six-channel polarization multiplexing in reconfigurable metasurfaces.

Dynamically tunable metasurfaces based on phase-change materials (PCMs) have become important platforms for realizing reconfigurable optical systems. Nevertheless, achieving multiple independent functionalities within a single device, particularly under polarization multiplexing, remains difficult due to limited design flexibility. In this study, we present a metasurface design framework that reaches the theoretical maximum of six independent phase modulation functions by simultaneously controlling the polarization states and the crystallinity of the PCM. This is implemented through a pixel-extension strategy, where each nanofin functions independently in amorphous state and is reorganized into superpixels with distinct optical responses in crystalline state. To support this, a forward filtering algorithm is developed to efficiently determine structural configurations under dual-state constraints. The effectiveness of the proposed approach is confirmed through two representative implementations, including dynamically switchable multifocal metalenses and multichannel holography. In addition, a progressive encoding strategy is introduced, which deliberately utilizes inter-state crosstalk to hierarchically embed optical information across material states. This compact and reconfigurable metasurface platform offers high functional density and flexible control, holding strong potential for applications in optical communication, information encryption, and adaptive display technologies.