Creating a spatial quasi-spherical focal spot and optical ring with controllable characteristics based on orthogonally superimposed dipoles antenna

Abstract

The 3D quasi-spherical focal spot and optical ring may find potential application value in fields like arbitrarily oriented particle capture and guidance, super resolution microscopy and optical capture. On the basis of the radiation pattern of the orthogonally superimposed dipoles antenna in a 4Pi focusing system, this paper firstly proposes an approach to create a central pure circular polarization three-dimensional (3D) quasi-spherical focal spot with higher longitudinal resolution. In addition, we also use the radiation pattern of the ring array antenna composed of orthogonally superimposed dipoles antenna elements to flexibly generate a pre-parameterizable and uniformly distributed optical ring. The simulated numerical results show that the method achieves a quasi-spherical focal spot with a slightly smaller longitudinal size (~0.31λ) than the transverse size (~0.41λ), and with the smallest volume (~0.0273λ 3 ). The position, radius, ring number and layer number of the constructed optical ring can be adjusted arbitrarily, determined by the parameters of the ring array antenna.