Cover story: Wang Z, Pan WK, He Y et al. Efficient generation of vectorial terahertz beams using surfacewave excited metasurfaces. Opto-Electron Sci 4, 240024 (2025).

With the rise of 5G, 6G, AI, and the Internet of Things, the demand for compact, high-speed, and low-power on-chip optical devices has increased. Traditional optical devices face challenges such as large size, low efficiency, and limited control. Metasurfaces, made of subwavelength artificial atoms, allow unique optical effects like anomalous reflection, surface wave excitation, and wavefront control. Recent advances show metasurfaces can decouple on-chip surface waves (SW) and control free-space radiation, enabling precise manipulation of phase and polarization.

This paper introduces a method for designing ultra-compact on-chip optical devices capable of generating complex vector optical fields (VOFs) under SW excitation, with experimental verification in the terahertz (THz) range. To advance this concept, researchers propose composite metasurfaces where single “artificial atoms” are replaced by 2×2 “artificial molecules.” These subunits radiate both left-handed (LCP) and right-handed circular polarization (RCP). By tuning local phase gradients and polarization states, the metasurface constructs macroscopic vector beams with specific wavefronts and polarization distributions, opening new possibilities for flexible light-field control.