Metasurface-Enabled On-Chip Three-Dimensional Optical Manipulation

Metasurface-based on-chip optical manipulation has attracted increasing attention recently, owing to its potential applications in single-cell analysis, atom cooling, and biosensing. So far, three-dimensional (3D) manipulation platforms based on metasurfaces remain unexplored, limiting the achievable degrees of freedom that are critical for practical applications. Here, we present an on-chip 3D manipulation platform with a multifunctional metasurface by leveraging the photonic spin Hall effect. The metasurface is designed via the combined use of geometric and propagation phases, with spatial multiplexing enabling independent control of different spatial degrees of freedom at distinct wavelengths. By varying the incident polarization or wavelength, the system can switch among four focal positions within a 3D volume, thereby enabling dynamic particle manipulation. Experimental results demonstrate stable and tunable 3D particle control, with lateral and longitudinal displacements of 24.2 and 90 μm, respectively. These results provide a platform for miniaturized 3D optical manipulation and highlight the potential of metasurface-based platforms for efficient on-chip manipulation.