Switchable terahertz orbital angular momentum Bessel beams based on spin-decoupled multifunctional reflective...

Area of Science:

• Optics and Photonics
• Metamaterials
• Terahertz Technology

Background:

• Terahertz (THz) beams with orbital angular momentum (OAM) offer unique properties for advanced applications.
• Developing switchable THz beams with controllable OAM modes is crucial for versatile functionalities.
• Metasurfaces (MTSs) provide a powerful platform for manipulating electromagnetic waves, including THz beams.

Purpose of the Study:

• To develop switchable terahertz multi-orbital angular momentum (OAM) Bessel beams (BBs) using a spin-decoupled reflective multifunctional metasurface (MTS).
• To establish a switchable physical model for predicting the characteristics of the generated BBs.
• To demonstrate the switchability and performance of the designed MTS for various polarization incidences.

Main Methods:

• Design and simulation of a spin-decoupled reflective multifunctional metasurface (MTS).
• Utilizing different polarization incidences (left-hand circular polarization (LCP), right-hand circular polarization (RCP), and linear polarization (LP)) to achieve beam switchability.
• Development of a physical model to calculate beam direction, OAM mode, polarization, and non-diffractive distance.

Main Results:

• Successfully generated switchable dual terahertz Bessel beams (BBs) with controllable OAM modes and polarization states.
• Achieved a high non-diffractive distance/aperture size ratio of 15 and a large beam deflection angle of up to 40°.
• Demonstrated high BB conversion efficiency up to 96% and validated the physical model with simulation results.

Conclusions:

• The proposed spin-decoupled MTS enables efficient switching of terahertz multi-OAM Bessel beams.
• The developed switchable BBs exhibit superior performance compared to previous MTS designs.
• Potential applications include high-capacity wireless communications, imaging, and non-destructive testing in the THz regime.