A Reconfigurable Non-Interleaved Bidirectional Janus Metasurface with Four Scattering Channels

Metasurfaces, as ultra-thin two-dimensional structures with subwavelength patterns, can achieve flexible control over beam phase, amplitude, and polarization. However, most existing metasurfaces can only control beams from a specific incident direction, limiting their potential applications. This paper proposes a non-interleaved, bidirectional multifunctional Janus metasurface, which can be used to control terahertz waves over the entire space. By integrating photosensitive silicon—a phase-change material whose properties can be modulated by light—the functionality of the Janus metasurface can be dynamically reconfigured through changes in illumination intensity. With two input parameters—electromagnetic wave propagation direction and the state of the photosensitive silicon—four independent beam control functionalities are realized. Based on the proposed four-channel metasurface, a beam focusing characterization half-adder is designed for simple optical computation. The Gerchberg-Saxton (GS) algorithm is then used to design four near-field imaging phase encoding distributions to validate the performance of the proposed four-channel metasurface. A series of simulation results indicate that the reconfigurable Janus metasurface effectively reduces crosstalk between channels, and the simulation results of each channel match the expected design. Our work is of great significance for advancing multifunctional, miniaturized metasurfaces, and the proposed metasurface devices have many potential applications in optical computation, imaging, and communication.