Abstract
Abstract Bessel beams have attracted considerable interest because of their unique non-diffractive, self-healing characteristics. Different approaches have been proposed to generate Bessel beams, such as using axicons, diffractive optical elements, composite holograms, or spatial light modulators. However, these approaches have suffered from limited numerical aperture, low efficiency, polarization-dependent properties, etc. Here, by utilizing dielectric Huygens metasurfaces as ultrathin, compact platforms by integrating the functionalities of Dammann gratings and axicons, we successfully demonstrate multiple Bessel beam generation with polarization-independent property. The number of two-dimensional arrays can be controlled flexibly, which can enhance information capacity with a total efficiency that can reach 66.36%. This method can have various applications, such as parallel laser fabrication, efficient optical tweezers, and optical communication.
Highlights
Metasurfaces, two-dimensional (2D) counterparts of metamaterials, are designed to modify the characteristics of electromagnetic waves, such as wavefront, intensity distribution, and polarization properties [1,2,3,4,5]
By utilizing an Huygens metasurfaces (HMSs) composed of a cylinder nanopost array, polarization-independent characteristic can be achieved for isotropic building blocks
Lin et al.: Bessel beam array generation by Huygens metasurfaces tool to divide it into many subdomains to provide multiple axicon phase-masks
Summary
Metasurfaces, two-dimensional (2D) counterparts of metamaterials, are designed to modify the characteristics of electromagnetic waves, such as wavefront, intensity distribution, and polarization properties [1,2,3,4,5]. Lin et al.: Bessel beam array generation by Huygens metasurfaces tool to divide it into many subdomains to provide multiple axicon phase-masks. This method is inefficient and suffers from inhomogeneity of energy distribution and interference-induced oscillations, which result in very low quality. Note the fact that a subdomain structure cannot reach high NA as compared with the proposed metasurface design in the same size In previous works, both in-plane surface wave and outof-plane free wave modulation have been demonstrated for Bessel beam generation with metasurfaces. Another work employed gradient cascaded metasurfaces to bend terahertz beams in anomalous refraction directions and to generate a non-diffractive Bessel beam under normal and oblique incident conditions [31] Such a cascaded metasurface is still very difficult to achieve in the optical regime. Multiple Bessel beam generations based on metasurfaces can significantly benefit applications in scanning microscopy, optical manipulation, and lithography to achieve a high spatial resolution and parallel processing
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