Fig. 1. (a) 3D Schematic of the plasmonic EA modulator. (b) Enlarged view of the cross-sectional area of the active E-O modulation region and (c) enlarged view of the Au slot waveguide with tapers to silicon waveguides.

Fig. 2. Simulated optical mode profiles for (a) the plasmonic slot waveguide with Np=Nb=1×1020  cm−3 and (b) the plasmonic slot waveguide with ITO at ENZ when Np=7.5×1020  cm−3. The inset shows the enlarged region with the ENZ ITO layer. Top view of optical field distributions at (c) the ON state (accumulation layer Nb=Np=1×1020  cm−3) and (d) the OFF state (accumulation layer Np=7.5×1020  cm−3). The optical field profile is plotted in log scale. (e) The propagation loss of the plasmonic slot waveguide at different peak carrier concentrations. (f) Transmission at the ON state and OFF state and the extinction ratio as a function of the optical wavelength.

Fig. 3. (a) Optical image of the plasmonic slot waveguide integrated with Si waveguides. (b) SEM image of the plasmonic slot waveguide. (c) Enlarged SEM image of the tapered region. (d) SEM image of the cross-sectional view of the slot waveguide.

Fig. 4. (a) Change of the measured (blue) and simulated (red) transmission with the applied gate voltage. (b) Left: measured static transmission spectra with no applied bias and 3.5 V bias. Right: measured ER with 3.5 V applied bias.

Fig. 5. Dynamic optical modulation testing results with −2 to 2 V sweep input bias voltage at 40 MHz.