Fully CMOS compatible subwavelength plasmonic slot waveguides for Si electronic-photonic integrated circuits

Subwavelength horizontal Al/SiO₂/Si/SiO₂/Al plasmonic slot waveguides with SiO₂ width at each side of ~15 nm and Si width of ~136, ~87, and ~43 nm are fabricated on SOI substrates using fully CMOS compatible processes. The propagation losses at 1550 nm TE are ~1.01, ~1.31, and ~1.56 dB/μm, respectively, as measured by the standard cutback method. A simple taper coupler with length of ~0.3-1 μm provides a high coupling efficiency of ~66%-79% between the plasmonic slot waveguide and the standard Si dielectric waveguide. The plasmonic slot waveguide can achieve a direct 90° bend with a very low bending loss of ~0.2-0.4 dB. The propagation, coupling, and bending losses depend weakly on wavelength in the c-band. The results demonstrate the potential for seamless integration of functional plasmonic devices in existing Si electronic-photonic integrated circuits.