Engineering topological interface states in metal-wire waveguides for broadband terahertz signal processing

Area of Science:

• Photonics and Metamaterials
• Terahertz Technology
• Topological Physics

Background:

• Terahertz (THz) waveguides are crucial for 6G communications, requiring efficient signal transport and manipulation.
• Metal-wire waveguides offer low-loss, low-dispersion propagation of THz pulses.
• Engraving grooves on metal-wire surfaces enables signal-processing functionalities.

Purpose of the Study:

• To design and demonstrate a novel plasmonic signal processor using topological interface states.
• To engineer a terahertz two-wire waveguide with multiscale groove structures exhibiting distinct topological invariants.
• To validate the experimental existence and robustness of topological interface states for signal processing.

Main Methods:

• Constructed a topological interface by connecting two multiscale groove structures with a π-shift difference in Zak phases.
• Experimentally investigated the transmission spectrum of the engineered two-wire waveguide.
• Analyzed the robustness of the topological interface states against structural disorders.

Main Results:

• Confirmed the existence of a topological interface state with a prominent transmission peak within the topological bandgap.
• Demonstrated that the topological interface resonance is highly robust against structural disorders.
• Showcased flexible control over the resonance quality factor.

Conclusions:

• The engineered topological interface states enable robust and controllable plasmonic signal processing in terahertz waveguides.
• This approach facilitates essential functions like band filtering, isolating, and solving linear differential equations.
• Paved the way for new-generation all-optical analog signal processors for terahertz networks, offering simplicity, speed, and reliability.