Metamaterials-based broadband generation of orbital angular momentum carrying vector beams

Abstract

We propose a simple approach to broadband generation of orbital angular momentum (OAM) carrying vector beams based on compact metamaterials. It consists of two concentric rings in a gold film, where each ring is composed of subwavelength rectangular apertures with gradually varied orientation. The subwavelength rectangular aperture serves as a localized spatial polarizer. We show the generation of different OAM-carrying vector beams with OAM charge number and polarization order varying from -3 to +3 using a 11.2×11.2 μm device. The extinction ratio can exceed 20 dB, and the operation bandwidth (1500 nm) can cover from 1000 to 2500 nm (from near-infrared to mid-infrared). The device provides three degrees of freedom (polarization order l, polarization of input beam σ, and initial orientation angle α(0)) to flexibly generate different OAM-carrying vector beams. We can use a single device to generate two OAM-carrying vector beams with opposite charge sign of OAM by simply controlling the polarization of the input beam. We further study the performance dependence of the designed metamaterials on the offset of the initial orientation angle, length, and width of the rectangular apertures. The obtained results indicate favorable fabrication tolerance.

Roadmap on structured light

“…Some of the first realizations of a microscopic diffractive optical element for thegeneration of an OAM were demonstrated about ten years ago (figures 15(a) and(b)) [104,105]. Recent progress in the field of nanofabrication and engineered optical materials, including metamaterials and metasurfaces, resulted in thede-monstration of a number of structured light converters based on various material platforms [104][105][106][107][108][109].…”

Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications

“…In this review article, we go over our recent progress in plasmonic and dielectric metasurface-assisted nanophotonic devices and their design, fabrication and applications, including the metasurface-based broadband and selective generation of orbital angular momentum (OAM) carrying vector beams [118,119], N-fold OAM multicasting using a V-shaped antenna array [120], metasurfaces on a conventional optical fiber facet for linearly-polarized mode (LP 11 ) generation [121], graphene split-ring metasurface-assisted terahertz coherent perfect absorption [122], OAM beam generation using a nanophotonic dielectric metasurface array [123] and Bessel beam generation and OAM multicasting using dielectric metasurface array [124].…”

Laguerre-Gaussian mode division multiplexing in multimode fiber using SLMs in VCSEL arrays

“…Recently, metameterials consisting two concentric rings in a gold film were used to generate OAM modes, where each ring is composed of subwavelength rectangular apertures which function as a localized spatial polarizer [24]. Spiralphased plates have also been fabricated to generate a coherent superposition of optical vortices with different winding numbers and surface reflection coefficients [25,26].…”