Straight Long-Range Surface Plasmon Polariton Waveguides with a Gap

Area of Science:

• Photonics and Plasmonics
• Nanophotonics
• Optical Waveguides

Background:

• Surface plasmon polaritons (SPPs) are electromagnetic waves propagating at metal-dielectric interfaces.
• Long-range SPPs (LR-SPPs) offer enhanced propagation distances compared to conventional SPPs.
• Gap-based SPP waveguides (G-SPPWs) are explored for their potential in integrated photonic circuits.

Purpose of the Study:

• To experimentally evaluate the optical characteristics of fabricated G-SPPWs.
• To determine the gap coupling and insertion losses in G-SPPWs with varying waveguide widths.
• To assess the performance of G-SPPWs in high-speed optical signal transmission.

Main Methods:

• Fabrication of 20-nm-thick G-SPPWs with a fixed 2 µm gap length.
• Experimental characterization of optical properties at a 1.55 µm wavelength.
• Optical signal transmission experiment at 2.5 Gbps.

Main Results:

• Gap coupling losses were found to be less than ~0.22 dB for SPP waveguide widths up to ~8 µm.
• Insertion losses were less than ~0.89 dB across the tested design range.
• A minimum insertion loss of ~0.45 dB was achieved with a 7 µm SPPW width.
• The G-SPPW demonstrated excellent eye opening in a 2.5-Gbps transmission experiment, successfully transferring both carrier wave and data signal.

Conclusions:

• G-SPPWs exhibit low propagation losses, making them suitable for integrated photonic applications.
• The gap in G-SPPWs can be functionalized for active control of SPP modes.
• G-SPPWs show promise as novel plasmonic modulation elements.