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In recent years, light with orbital angular momentum, or the so-called vortex beams, has been the subject of intense research, due to its applications in microscopy, telecommunications, and investigating the selection rules. Many efforts have been devoted to generate vortex beams using metasurfaces and metamaterials. However, most of them lack key properties in controlling the polarization, directionality and intensity of the light which is generated and directed from a localized radiation sources such as electron-beam induced emission. Recently, a photon-sieve structure has been designed, developed and characterized as an electron-driven photon source, which is formed by specific ordering of nanoholes in different sizes and lattices forming a helical arm in a thin layer of gold. Electron beams in a scanning electron microscope interacts with the surface of a photon-sieve structure acting as a broadband source of optical excitation. Both Chain plasmons and chiral surface plasmons are excited in this structure resulting in vortex beams propagating in vacuum. Here, we design a photon sieve structure that can generate vortex pairs, i.e., optical beams with entangled phase singularities of opposite signs associated with the topological charges. This phenomenon is experimentally studied utilizing a cathodoluminescence detector facilitated with angle-resolved mapping, polarimetry, and spectroscopy methods. Data obtained from the polarimeter suggests that the rotating behaviour of the vortices are caused by their orbital angular momentum rather than the polarization. Experimental data are further confirmed by numerical simulations suggesting that the interference between the propagating polaritons and reflection from the void ring is the main reason for observing counter propagating plasmons with opposite chirality in experimental images. We anticipate that this work presents a systematic method towards designing new generation of metasurfaces with the possibility to control directivity, angular momentum, and energy of the light beams.
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