Generation of optical cage arrays with tunable dark regions based on magneto-electric dipole antennas

Abstract

Optical cages have recently received extensive research and attention due to their potential applications in optical cloaking, microscopic imaging, and trapping particles or atoms. However, the creation of a controllable spatial multi-optical cage array with tunable dark regions comes with a great challenge, which limits the effectiveness of the above applications. To this end, we analyze the radiation pattern of a reverse-focused magneto-electric dipole antenna in a 4Pi optical focusing system. It has been found that three-dimensional (3D) optical cages with different dark regions can be produced by using magneto-electric dipoles with different combination coefficients K. Numerical results indicate that the value of K can be employed to adjust the shapes and sizes of the dark regions, and specifically, when K equals 0.8209, it allows the realization of a perfectly spherical dark region with null central intensity and minimal volume. Furthermore, it is possible to flexibly create spatial multi-optical cage arrays with specified orientations, adjustable numbers, and controllable positions by constructing spatial antenna arrays according to practical requirements. This work may enhance its ability to meet the distinct requirements for optical cages across diverse fields and catalyze the advancement of multi-particle optical trapping and manipulation.