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. 2017 Jan 16;7:40479.
doi: 10.1038/srep40479.

Hybrid Dielectric-loaded Nanoridge Plasmonic Waveguide for Low-Loss Light Transmission at the Subwavelength Scale

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Hybrid Dielectric-loaded Nanoridge Plasmonic Waveguide for Low-Loss Light Transmission at the Subwavelength Scale

Bin Zhang et al. Sci Rep. .
Free PMC article

Abstract

The emerging development of the hybrid plasmonic waveguide has recently received significant attention owing to its remarkable capability of enabling subwavelength field confinement and great transmission distance. Here we report a guiding approach that integrates hybrid plasmon polariton with dielectric-loaded plasmonic waveguiding. By introducing a deep-subwavelength dielectric ridge between a dielectric slab and a metallic substrate, a hybrid dielectric-loaded nanoridge plasmonic waveguide is formed. The waveguide features lower propagation loss than its conventional hybrid waveguiding counterpart, while maintaining strong optical confinement at telecommunication wavelengths. Through systematic structural parameter tuning, we realize an efficient balance between confinement and attenuation of the fundamental hybrid mode, and we demonstrate the tolerance of its properties despite fabrication imperfections. Furthermore, we show that the waveguide concept can be extended to other metal/dielectric composites as well, including metal-insulator-metal and insulator-metal-insulator configurations. Our hybrid dielectric-loaded nanoridge plasmonic platform may serve as a fundamental building block for various functional photonic components and be used in applications such as sensing, nanofocusing, and nanolasing.

Figures

Figure 1
Figure 1. Schematics of the proposed HDLNRPW.
(a) 3D layout of the hybrid waveguide. (b) Cross-section of the structure. The hybrid configuration consists of a silicon nanoridge-loaded semi-infinite silver substrate, which is separated from an upper silicon slab by the silica layer. The upper silicon slab has a width of w and a height of h, whereas the lower silicon nanoridge has a radius of r. The gap size, which is defined as the smallest distance between the lower and upper silicon nanostructures, is denoted by g. The silicon nanoridge is supposed to be at the center position (along x axis) with respect to the upper silicon slab unless stated otherwise.
Figure 2
Figure 2
2D and 1D normalized electric field distributions for (a)–(c) HDLNRPW, and (d)–(f) traditional HPW. For both structures, the dimensions of the rectangular-shaped silicon slabs are fixed at w = h = 200 nm, while their gap sizes were both chosen as g = 5 nm. The radius of the silicon nanoridge was r = 20 nm. The electric fields were normalized with respect to the power flow in each structure. The 1D field profiles show the normalized electric fields along the center of the gap region.
Figure 3
Figure 3. Modal properties and field distributions of HDLNRPWs with different g and r.
(a)–(d) Dependence of modal characteristics on the radius of the nanoridge (r): (a) modal effective index (neff); (b) propagation length (L); (c) normalized mode area (Aeff/A0); (d) figure of merit (FoM). (e)–(i) Normalized electric field distributions for typical waveguides (corresponding to the configurations indicated in (c)): (e) g = 5 nm, r = 5 nm; (f) g = 5 nm, r = 50 nm; (g) g = 10 nm, r = 30 nm; (h) g = 50 nm, r = 5 nm; (i) g = 50 nm, r = 50 nm. All the fields are normalized with respect to the power flow in the cross-sections.
Figure 4
Figure 4. Normalized optical power (NOP) vs. gap size (g) for HDLNRPWs with different silicon nanoridges.
Figure 5
Figure 5
2D and 1D normalized electric field distributions for (a)–(c) HDLNRPW with a square nanoridge, (d)–(f) HDLNRPW with a triangular nanoridge, and (g)–(i) traditional HPW. For all three waveguides, the sizes of rectangular-shaped silicon slabs were w = h = 200 nm, whereas their gap sizes were 5 nm. The width of the square silicon nanoridge was 20 nm. The structure in (d) had an equilateral triangular silicon nanoridge of height 20 nm. For all three structures, the electric fields were normalized with respect to the power flow in each structure. The 1D field profiles show the normalized electric field along the center of the gap region.
Figure 6
Figure 6. 2D schematics of two typical modified HDLNRPWs.
(a) MIM type hybrid waveguide with double silicon nanoridges; (b) IMI type hybrid waveguide with double silicon nanoridges.
Figure 7
Figure 7. 2D and 1D electric field profiles of guided low-loss plasmonic modes for MIM type and IMI type HDLNRPWs.
(a)–(c) MIM type hybrid waveguide, whose geometric parameters were w = h = 200 nm, r = 20 nm, and g = 5 nm; (d)–(f) IMI type hybrid waveguide with structural parameters as: w = h = wm = 200 nm, tm = 15 nm, r = 20 nm, and g = 5 nm.

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