Research On Left-hand Torque Based On Metasurface

Since the invention of optical tweezers,optical manipulation has been widely used in various scientific areas,such as atomic physics,optics and biological science.With the rapid progress of nanotechnology,optical manipulation has made significant progress in the application of subwavelength and nano-sized particles.Optical force can be used to achieve optical binding,trapping and sorting.the study of optical forces helps reveal the nature of light interactions,which provides considerable potential applications in a variety of scientific fields and everyday life.Optical rotation is an important research direction of optical manipulation.In this paper,optical rotation realized by metasurfaces is proposed,which is designed to apply in near-infrared,visible light and microwave band.Based on the calculation and analysis of optical torque on metasurface,and the torque phenomenon that meets the left-hand effect is achieved.Firstly,the realization of optical rotation is analyzed in this paper.Optical momentum can be generated by using photon’s linear momentum,spin angular momentum and orbital angular momentum.The calculation method of optical torque by using Maxwell stress tensor is proposed.According to the introduction of metasurface theory,the left-hand torque phenomenon based on metasurface is proposed,and the method of realizing left-hand is given.Dielectric structure and double-layer metallic split ring metasurfaces are proposed in this paper.Based on the design principle of phase shift unit,the half-wave plate unit cells,which are designed to convert incident cicular polarized wave to its cross-polarization,are applied to near-infrared,visible light and microwave bands.By designing the spatial arrangement of the unit cells,metasurfaces that generate vortex beams with different orbit angular momentums is constructed.Finally,by simulating the distribution of the electromagnetic field in the space,the Maxwell stress tensor is used to calculate the value of the optical torque.The simulation result shows that the optical torques under different vortex numbers are in a linear relationship,which is identical to theoretical analysis,and the left-hand torque based on metasurface is achieved.This paper provides an important theoretical basis for the generation of left-hand torque and contrubutes to the further development of the field of optical rotation.