Quarter-Millimeter Propagating Plasmons in Thin-Gold-Film-Based Waveguides for Visible Spectral Range

A series of long-range plasmonic waveguides based on a thin three-layer Al
₂
O
₃
/gold/Al
₂
O
₃
film operating in the visible spectral range have been studied experimentally and theoretically. For long-range plasmonic waveguides having identical structure but different lengths, the propagation length of plasmonic waves was determined to be 250 ± 15 μm at λ = 765 nm and was in a very good agreement with the theoretical value obtained through numerical modeling. The demonstrated propagation length is the highest one for the gold film-based plasmonic waveguides described in the literature for a uniform (non-photonic-crystal) substrate in the UV, visible, and near IR (up to 1 μm) spectral ranges, which is due to high technological quality of the fabricated waveguides and optimized three-layer structure. The proposed waveguides could find applications in optical interconnects and guided-wave optical sensors.