Encoding metasurface lens with controllable focal shift

Abstract Near-field electromagnetic focusing has emerged as a research hotspot due to its potential in wireless communication and sensing applications. Metasurface lenses play a key role in enabling efficient near-field focusing. In this work, we design a metasurface lens based on 3-bit encoding and the geometric phase principle, achieving a focusing efficiency of 72% and enabling efficient on-axis focusing. In coding metasurfaces, precise control over the direction of the scattering pattern is achieved by modulating the phase profile through Fourier-based operations, in conjunction with the principle of scattering pattern shift. The convolution and superposition of the coded lens phase with a spatial gradient phase sequence enable the focal point to shift freely along the horizontal, vertical, and combined directions. This strategy enables the splitting of a single focal point into dual foci to achieve focal shift, which can be further extended to realize a four-focus spatial arrangement within the focal plane, allowing for control of focal positions across the entire spatial domain. The flexibility of the scattering pattern shift principle in electromagnetic wave manipulation is validated, providing new insights for the design of unconventional lenses and enabling continuous, multi-angle, and free control of lens focal points.