Manipulating multipole resonances in spoof localized surface plasmons for wideband filtering

Area of Science:

• Electromagnetics and Plasmonics
• Metamaterials and Nanophotonics

Background:

• Spoof localized surface plasmons (LSPs) are typically limited to fixed multipole resonances.
• Existing LSP structures often lack tunability and reconfigurability for advanced applications.

Purpose of the Study:

• To propose and validate a method for generating tunable multipole resonances in LSPs.
• To demonstrate the application of the proposed LSP structure in a high-performance bandpass filter (BPF).

Main Methods:

• Theoretical analysis and numerical simulations of complementary LSPs with and without slits.
• Design, fabrication, and measurement of a single-layer bandpass filter utilizing the proposed LSP structure.
• Investigation of dynamic tunability using varactors or diodes.

Main Results:

• The addition of a slit introduces new boundary conditions and modes, enabling tunable multipole resonances.
• The designed BPF achieved a wide fractional bandwidth of 42.7% (2.5 GHz) with low insertion loss (|S21| within 1 dB).
• The structure exhibits a flat group delay and a compact size (0.136 wavelength radius).

Conclusions:

• Adding a slit to complementary LSPs is an effective method for generating tunable multipole resonances.
• The proposed LSP structure offers a promising platform for compact, high-performance, and reconfigurable filters in microwave and terahertz frequencies.
• The dynamic control of slits opens avenues for reconfigurable metamaterial devices.