Emission of orbital angular momentum based on spoof localized surface plasmons

Area of Science:

• Electromagnetics and Wave Phenomena
• Metamaterials and Plasmonics
• Microwave Engineering

Background:

• Orbital angular momentum (OAM) offers unique properties for advanced communication systems.
• Spoof localized surface plasmons (LSPs) provide a promising platform for manipulating electromagnetic waves at microwave frequencies.
• Generating OAM modes efficiently at microwave frequencies remains a challenge.

Purpose of the Study:

• To demonstrate a novel approach for generating orbital angular momentum (OAM) vortex modes.
• To utilize spoof localized surface plasmons (spoof LSPs) for OAM generation in the microwave spectrum.
• To experimentally validate the proposed OAM-mode emitter design.

Main Methods:

• Theoretical modeling and experimental validation of spoof LSPs on a textured metallic surface.
• Excitation of orthogonal spoof LSP modes using a microstrip line and two feeding ports.
• Superposition of orthogonal modes with ±90° phase retardation using a hybrid coupler.
• Conversion of surface waves to radiated vortex waves via a circularly arranged dipole array.

Main Results:

• Successful generation of fundamental and high-order spoof LSP modes.
• Demonstration of OAM-vortex mode generation through superposition of orthogonal modes.
• Fabrication and measurement of an OAM-mode emitter with indices of ±3.
• Excellent agreement between simulated and experimental near-field and far-field results.

Conclusions:

• The proposed method effectively generates OAM vortex waves using spoof LSPs at microwave frequencies.
• The designed OAM-mode emitter shows high performance and validates the theoretical approach.
• This work paves the way for OAM-based applications in microwave communications and sensing.