Engineering arrays of diffraction-limited hollow tubes and doughnut spots with prescribed distributions

Abstract

Based on the principle of antenna pattern multiplication as the product of the element pattern and the array factor, a simple and flexible method to generate diffraction-limited optical hollow-tube and doughnut-spot arrays with predetermined properties is proposed. This approach can be realized in a 4Pi focusing system by reversing the field radiated from the collinear antenna array whose elements are isotropic magnetic current sources. Both hollow tubes and doughnut spots produced by this method are pure azimuthally polarized fields whose intensity distribution is nearly unchanged along the entire depth of focus. Numerical results show that the appearance and position of the focal field is determined by the element pattern and the array factor, respectively. These peculiar optical focal fields may find applications in multi-particle trapping and manipulation, materials processing, data storage, super-resolution optical microscopy and optical lithography.

Creating spatial doughnut-spot arrays and double-helix focal fields with prescribed characteristics

“…In 2011, Wang et al [15] established an ultra-long (∼8λ) diffraction-limited optical tube through the radiation field of an array composed of three groups of amplitudeoptimized co-located magnetic and electric dipoles along the optical axis. In 2019, Yu et al [16] proposed a non-optimized method for generating two-dimensional doughnut spots and hollow tubes along the z axis with predetermined characteristics using the radiation field of virtual magnetic-currentsource antenna arrays. In contrast, over the past decade, there has been relatively limited research on arbitrarily spatially directed doughnut-spot arrays and three-dimensional (3D) double-helix focal fields, which may find potential applications in multi-particle trapping and manipulation [17][18][19][20][21], optical imaging [22][23][24][25], single-molecule imaging [26], and complex opto-fluidics [27].…”

Creation of a 3D double-helix focal field with controllable characteristics

“…An ultra-long (8λ) diffraction-limited hollow optical tube was constructed by co-located magnetic-electric dipole arrays [1] . A two-dimensional doughnut-spot array was created by utilizing the radiation pattern of magnetic current sources antenna [2] . However, there has been limited research on three-dimensional (3D) doublehelix focal fields that could potentially be applied in complex opto-fluidics, high-resolution imaging, and optical imaging.…”