Multichannel terahertz quasi-perfect vortex beams generation enabled by multifunctional metasurfaces

Area of Science:

• Terahertz (THz) photonics
• Metasurface optics
• Orbital Angular Momentum (OAM) applications

Background:

• Vortex beams carrying orbital angular momentum (OAM) are crucial for advanced terahertz research.
• Generating multichannel and divergence-controllable THz vortex beams is essential for OAM-based THz technologies.

Purpose of the Study:

• To introduce and experimentally demonstrate quasi-perfect vortex beams (Q-PVBs) with controllable divergence.
• To achieve multichannel Q-PVBs generation using all-dielectric multifunctional metasurfaces.

Main Methods:

• Designing multifunctional metasurfaces by superimposing specific phase functions.
• Generating and characterizing multiple Q-PVBs with different topological charges and separated focal points.
• High-resolution terahertz electric field measurements to assess beam quality and properties.

Main Results:

• Successfully generated Q-PVBs with divergence angles controllable and independent of topological charge.
• Demonstrated multichannel Q-PVB generation, producing four channels with distinct topological charges.
• Characterization confirmed the good quality and broadband characteristics of the generated Q-PVBs.
• Q-PVBs exhibited smaller divergence angles and thinner ring widths compared to conventional perfect vortex beams.

Conclusions:

• The proposed all-dielectric metasurfaces enable compact, multichannel generation of vortex beams.
• This technology offers a promising pathway for advancing OAM-related terahertz research, including mode division multiplexing and plasmonic enhancement.