Fig. 3
On-chip extreme skin-depth (e-skid) waveguides. a Ideal on-chip e-skid waveguide; light is confined by total internal refection inside the core and as the effective anisotropy of the multilayer metamaterial cladding is increased, evanescent waves of TE-like modes decay faster in the cladding in comparison with the field in strip waveguides (\(\varepsilon _{2z} = 1\)). Note that \(\varepsilon _{2x} = 1\) for all cases. b The simulated electric field profile at the center of the e-skid waveguide with multilayer (green) and homogenized metamaterial (\(\varepsilon _{2x} = 1.85\) and \(\varepsilon _{2z} = 6.8\)) (red) claddings, in comparison with a strip waveguide (blue). Inset shows the SEM image of the fabricated e-skid to strip waveguide transition. c, d Schematic and field profiles of c realistic e-skid waveguide with multilayer claddings and d its equivalent model with EMT claddings. e, f Effective refractive indices \(\left( {n_{{\mathrm{eff}}} = k_z \hskip -3.5pt \prime /k_0} \right)\) and g, h normalized decay constants (\(k_x \hskip -2.5pt {\prime\prime} /k_0 = 1/\delta k_0\)) of the e-skid waveguide as functions of the core width w0 and filling fraction ρ: with e, g multilayer and f, h EMT claddings, respectively. Geometric parameters are h0 = 220 nm, w0=350 nm, Λ = 100 nm, ρ = 0.5, and N = 5, unless otherwise indicated. The free space wavelength is λ=1550 nm. Simulations confirm that the cladding achieves effective all-dielectric anisotropy as well as the increased decay constant of evanescent waves outside the core
