Hitherto, methods to generate optical vortex beams have been widely researched, ranging from mode conversion to diffractive optical elements. However, bulky-sized traditional methods are unsuitable for nanophotonic systems, metasurface has become an alternative option for generating optical vortices. In this paper, a metasurface combining dynamic and geometric phases is proposed. Under the incidence of circular polarized light, optical vortices with different topological charges can be generated simultaneously by a single metasurface. The dynamic phase makes the topological charge of the vortex light vary with distance. The intensity distribution and relative distance of the focused vortices can be manipulated with different focal length of the metasurface. This method provides a new design to generate different vortices in a single device and has potential applications in particle capture and integrated optical systems.
Optical beam carrying orbital angular momentum(OAM) exhibits profound potential in optical communications, micromanipulation and other related fields due to its helical wavefront. However, complex configuration of manipulating optical vortices have hindered the realization of nanophotonic systems. Recently, owing to the ultrathin structure, plasmonic metasurfaces based on abrupt phase shift have aroused appreciable interest. In this paper, we introduce a multifunctional device that integrates a focusing apparatus and an orbital angular momentum generator by the use of the plasmonic metasurfaces. This metasurface combining Archimedean spirals and spatially variant nanoslits achieves plasmonic focusing and an optical needle in the near- and far-field, respectively. Moreover, generation of optical vortex beams is shown in the far- and near-field simultaneously, where light field can be arbitrarily manipulated. We expect this work to have further applications in integrated photonic systems.
Due to the spin-orbit Hall effect of light, the intensity distribution of the reflected light is related to the incident angle, spin-orbital angular momentum and the refractive index of the reflective surface. In this paper, we research the spin-orbit Hall effect in the reflection with incident vortex lights carrying spin and orbital angular momentum. Then, the orbital angular momentum (OAM) spectrum of the reflected light are calculated. Subsequently, owing to the fact that the light field is redistributed after reflection, we propose a method for measuring the refractive index of optical materials based on the OAM spectrum of the reflected light. This measurement technique has the advantage of high sensitivity and strong anti-interference ability. We expect this work to contribute to other fields of precise measurements.
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