Long-range surface plasmon polariton waveguides embedded in fluorinated polymer

Area of Science:

• Photonics and optical engineering
• Materials science for optical devices
• Nanophotonics and plasmonics

Background:

• Surface plasmon polaritons (SPPs) offer unique light-matter interactions for optical waveguides.
• Achieving low propagation loss in SPP waveguides is crucial for practical applications.
• Perfluorocyclobutane (PFCB) polymer offers low absorption for optical applications.

Purpose of the Study:

• To present low-attenuation waveguides utilizing long-range surface plasmon polaritons (LRSPPs).
• To optimize waveguide design and fabrication for reduced propagation loss.
• To investigate and enhance optical fiber coupling efficiency for LRSPP waveguides.

Main Methods:

• Fabrication of thin gold (Au) stripes embedded in perfluorocyclobutane (PFCB) polymer.
• Optimization of cladding material and fabrication processes to minimize propagation loss.
• Theoretical and experimental analysis of coupling efficiency with optical fibers, varying waveguide dimensions.
• Finite-difference mode solver used for calculating surface plasmon polariton (SPP) mode distributions.

Main Results:

• Achieved a new low propagation loss of <2.0 dB/cm for a 4 microm wide LRSPP waveguide.
• Identified optimal cladding thickness for reduced coupling loss, correlating with fiber mode diameter.
• Demonstrated improved coupling efficiency by matching cladding thickness to fiber mode diameter.
• Proposed a multilayer cladding structure with varying refractive indices to further minimize insertion loss.

Conclusions:

• Low-loss LRSPP waveguides can be realized in Au-PFCB structures.
• Waveguide width, cladding properties, and fabrication are critical for performance.
• Understanding mode distribution is key to optimizing fiber-to-waveguide coupling.
• Multilayer cladding designs hold potential for further reducing insertion losses in plasmonic devices.