Optical manipulation of Rayleigh particles by metalenses-a numerical study

Based on the focusing feature of a metalens, we numerically studied its application in optical manipulation of Rayleigh particles. Three types of metalenses-point focusing, line focusing, and line focusing with phase gradient-were designed. Simulation results using the finite-difference time-domain method showed that the incident optical beams could be focused into a spot or a line for stable particle trapping. Through engineering a gradient phase in the direction of the focal line, the proposed metalens can push the particles along the line. This provides a unique capability to move particles along a line without the need of any mechanical movement. Given its thin sheet structure and compactness, the proposed metalens can be easily integrated into microfluidic and optical tweezers systems, and it can find potential applications in optical sorting of biological cells.