Transmission Continuous Meta-Grating for Generating Wide-Band Low-to-High Order OAM With Extremely High Mode Purity

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Abstract
This paper presents a novel continuous dielectric meta-grating array (DMGA) for generating wideband, high-performance transmission orbital angular momentum (OAM) vortex beams with high mode purity. A broadband meta-grating unit (MGU) was designed and modeled theoretically, including a detailed analysis of its design process. Simulations and theoretical calculations show that, in the 26-39 GHz (40%), the unit achieves a 180° transmission phase and a transmission coefficient over 0.9. The array patterning was determined using a grating function. The DMGA is composed of continuously spatially varying grating strips, effectively preventing issues caused by array discontinuity such as inter-atom coupling and discontinuous step phase changes, which could lead to vortex beam distortion and low purity. Simulations show that the DMGA generates broadband, high-performance vortex beams with high mode purity for mode orders l = 2, 3, 4, 5, 6, 7, 8, 9, and 10, exhibiting advantages in generating high-quality, high-order OAM beams. Additionally, it exhibits frequency-aperture size insensitivity, enabling miniaturization and customization of aperture sizes. Finally, the measurement confirms the effectiveness.
Funding Information
  • Natural Science Foundation of China (62301003, 62201192)
  • Research Funds of Center for Big Data and Population Health of Institute of Health and Medicine (JKS2022004)
  • China Postdoctoral Science Foundation (2023M730006)
  • Postdoctoral Fellowship Program of China Postdoctoral Science Foundation (GZC20230005)
  • Key Natural Science Research project of Anhui Higher Education Institutions (2022AH050070)

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