Mode properties in metallic and non-metallic plasmonic waveguides

Area of Science:

• Plasmonics
• Materials Science
• Nanophotonics

Background:

• Non-metallic plasmonic materials are gaining attention for tunable properties and low loss in plasmonic waveguides.
• Ultrahigh mode confinement is crucial for efficient plasmonic waveguides.

Purpose of the Study:

• To analyze and compare the mode properties of plasmonic waveguides using noble metals, aluminum-zinc-oxide (AZO), and titanium nitride (TiN).
• To evaluate propagation length and mode size as figures of merit for different plasmonic waveguide materials.

Main Methods:

• Investigated mode properties of four plasmonic waveguide types: noble metals, AZO, and TiN.
• Fabricated AZO/ZnO films with tunable carrier densities (1.8×10^17 to 8.6×10^20 cm^-3) using pulsed-laser deposition.
• Characterized material properties, including permittivity, around 1550 nm.

Main Results:

• AZO exhibits the smallest imaginary part of permittivity in the near-infrared region.
• AZO waveguides show propagation lengths comparable to copper but shorter than gold and silver.
• AZO and TiN waveguides achieve smaller mode sizes due to higher real permittivity, especially in insulator-metal-insulator and dielectric-loaded configurations.
• Metal-like properties (negative real permittivity) were observed in AZO/ZnO films around 1550 nm.

Conclusions:

• AZO presents a promising non-metallic material for plasmonic waveguides due to its favorable optical properties.
• AZO and TiN waveguides offer advantages in mode confinement compared to traditional noble metal waveguides.
• The tunable carrier density and observed metal-like behavior position AZO as a strong candidate for plasmonic optical interconnects.