Experimental Demonstration of Horizontal Nanoplasmonic Slot Waveguide-Ring Resonators With Submicrometer Radius

Ultracompact plasmonic waveguide-ring resonators (WRRs) based on horizontal Cu/SiO₂/Si/SiO₂/Cu nanoplasmonic slot waveguides are fabricated using standard Si complementary metal-oxide-semiconductor (CMOS) technology for operation at telecommunication wavelengths. Efficient coupling between the ring and bus waveguides is achieved through a small aperture in the metallic sidewalls of the waveguides. A WRR with a radius 0.91 μm (cavity mode volume of ~0.145 μm³ ) is characterized, exhibiting an insertion loss of ~2.4 dB, an extinction ratio of ~28 dB at the 1596-nm resonance (corresponding to the seventh cavity mode), a free-spectral range of ~143 nm, and a quality factor of ~638. The demonstrated WRR can be used as a building block for various functional nanoplasmonic devices to be seamlessly integrated in the existing Si photonic and electronic integrated circuits.