Metasurface for oscillatory spin splitting along the optical path

Spin splitting of light originates from the interplay between the polarization and spatial degrees of freedom as a fundamental constituent of the emerging spin photonics,providing a prominent pathway for manipulating photon spin and developing exceptional photonic devices.However,previously relevant devices were mainly designed for routing monotonous spin splitting of light.Here,we realize an oscillatory spin splitting of light via metasurface with two channel Pancharatnam–Berry phases.For the incidence of a linearly polarized light,the concomitant phases arising from opposite spin states transition within pathways of the metasurface induce lateral spin splitting of light with alternately changed transport direction during beam guiding.We demonstrate the invariance of this phenomenon with an analogous gauge transformation.This work provides a new insight on steering the photon spin and is expected to explore a novel guiding mechanism of relativistic spinning particles,as well as applications of optical trapping and chirality sorting.