Highly localized linear array of optical rings with multiple tunable degrees of freedom

Abstract

By combining time-reversal techniques and antenna radiation theory, we present a simplified approach to generate a novel highly localized linear array of optical rings with multiple tunable degrees of freedom, without complex optimization of the pupil field. Utilizing the radiation field of a magnetic current line source (MLS) with a periodic cosine-squared tapered distribution, we inversely obtain the pupil field required to generate the desired focal field. The characteristics of the focal field, after focusing by a 4π focusing system, are evaluated through vector Debye diffraction integral theory. The results reveal that the focal field forms a linear array of identical optical rings aligned along the direction of the MLS. Each ring exhibits a purely azimuthal polarization with only azimuthal optical field components. The number of rings is determined by the periodic parameters of the magnetic current, while the position and spacing of the rings depend on both the length and periodic parameters of the MLS. The highly localized, tunable linear array of optical rings holds significant potential for applications in optical parallel processing, multi-point particle trapping, and transportation.