Thin-wall tubes for coupling terahertz waves to metal wires

Area of Science:

• Optics and Photonics
• Materials Science
• Electromagnetism

Background:

• Metal wires are key for guiding terahertz (THz) surface plasmon polaritons.
• Efficiently coupling THz waves to these waveguides remains a challenge.

Purpose of the Study:

• To propose a thin-wall tube structure for ultrahigh-efficiency THz wave coupling to metal wires.
• To investigate the factors influencing coupling efficiency.

Main Methods:

• Mode-overlap calculations were performed to determine coupling efficiency.
• Analysis focused on field distributions, polarization directions, and wave vectors.
• Simulations covered THz frequencies from 0.2-3 THz with a 0.5 mm wire radius.

Main Results:

• The proposed thin-wall tube achieved coupling efficiencies between 84% and 94% across the 0.2-3 THz range.
• A maximum efficiency of 94% was observed at 0.5 THz.
• This significantly surpasses efficiencies reported for previous coupling methods.

Conclusions:

• The thin-wall tube offers a highly efficient method for THz wave coupling to metal wires.
• Optimal coupling occurs when the outer tube radius matches the wire radius and propagation constants are equal.