Holographic multi-focus multifunctional metalens realises particle capture, rotation and sorting

Optical tweezers, with their excellent manipulation precision, have become a vital tool for exploring the microscopic world and have significantly advanced research in physical and biological sciences. However, enhancing system integration and multifunctionality remains a critical challenge. In this study, we adopt a shared aperture approach to design and construct a polarisation-insensitive multifunctional optical tweezer system with a high numerical aperture. This system can capture, rotate, and sort various nanospheres in parallel. Through theoretical analyses and numerical simulations, we propose an innovative method to coaxially focus a Gaussian spot with a vortex spot, generating a unique light field for conducting photodynamic analyses of particles. Furthermore, our method enables the generation of numerous arbitrary-state light fields in free space with uniformly normalised electric field strengths. These foci ensure uniform light field distribution and consistent particle capture, enhancing the precision of optical tweezers in biophysics, materials science, and nanotechnology. This work also provides novel theoretical insights for microscale precision manipulation and analysis.