Terahertz quasi non-diffraction Bessel vortex beam generation using three lattice types reflective metasurface

Area of Science:

• Terahertz technology
• Metasurface optics
• Optical communications

Background:

• Orbital angular momentum (OAM) manipulation faces challenges in bandwidth, divergence, and mode purity for terahertz (THz) applications.
• The sixth-generation (6G) communication system requires advanced OAM manipulation techniques.

Purpose of the Study:

• To propose a broadband high-order Bessel vortex beam carrying multiple OAM modes reflective metasurface in the terahertz domain.
• To investigate the impact of different lattice types on OAM mode purity.

Main Methods:

• Design and simulation of a broadband reflective metasurface for THz OAM.
• Comparative analysis of square, triangular, and concentric ring lattice structures.
• Evaluation of OAM vortex beam characteristics, including divergence and mode purity.

Main Results:

• The proposed metasurface effectively alleviates the diffracting divergence of OAM vortex beams.
• Simulation results align with theoretical predictions for OAM beam characteristics.
• The concentric ring lattice exhibited superior performance in maintaining OAM mode purity compared to square and triangular lattices.

Conclusions:

• The developed reflective metasurface offers a promising solution for broadband THz OAM manipulation.
• Concentric ring lattices are optimal for achieving high mode purity in OAM vortex beams for 6G communications.