Polarization-sensitive metalens generates superposed optical force field for nanoparticle manipulation

Conventional techniques for optically manipulating micro- and nanoparticles often require the combination of multiple optical components to achieve specific functionalities, making it challenging to meet the demands of integrated and miniaturized applications. In contrast, metalenses offer significant advantages in terms of size, weight, and integration level. As such, optical tweezers (OT) and optical spanners (OS) based on metalenses have garnered considerable research interest. This paper presents a novel design based on a phase-change metasurface composed of meticulously engineered geometric-phase and dynamic-phase meta-atoms. By dynamically modulating the polarization state of the incident light, on-demand switching and integrated control of optical trapping and rotation functions can be achieved. To evaluate the performance of the proposed design, numerical simulations were conducted to analyze the focusing spot characteristics and particle manipulation effects. The results demonstrate that the phase-change metasurface can simultaneously generate a coaxial vortex field at the focal spot, enabling stable three-dimensional optical trapping and tunable orbital angular momentum transfer. It efficiently accomplishes both particle trapping and rotation. Compared to previous approaches that struggled to integrate both OT and OS functionalities on a single metasurface, the designed phase-change metasurface realizes functional integration and reconfigurability, thereby better fulfilling the requirements for on-chip particle manipulation systems. This study highlights the potential of polarization modulation in multifunctional optical field shaping.