Abstract
This study reports a symmetric hybrid plasmonic waveguide consisting of a cylindrical metal nanowire surrounded by low-index SiO₂ and high-index Si covered with SiO₂. The symmetric circumambience relative to the metal nanowire significantly facilitates the present design to minimize the energy attenuation resulting from Ohmic losses while retaining highly confined modes guided in the low-index nanoscale gaps between the metal nanowire and the high-index Si. The geometric dependence of the mode characteristics on the proposed structure is analyzed in detail, showing long propagation lengths beyond 10 mm with normalized mode areas on the order of 10⁻². In addition to enabling the building of long-range plasmonic circuit interconnects, the compactness and high-density integration of the proposed structure are examined by analyzing crosstalk in a directional coupler composed of two such waveguides and bending losses for a 90° bend. A relatively short coupling length of 1.16 μm is obtained at a center-to-center separation of 0.26 μm between adjacent waveguides. Increasing the separation to 1.65 μm could completely prevent coupling between waveguides. Power transmission exceeds 80% in the case of a 90° bend with small radius of curvature of 0.5 μm. Moreover, the dependence of spectral response on coupling length and the transmission of a 90° bend, ranging from telecom wavelengths of 1.40 to 1.65 μm, are investigated. Over a wide wavelength range, a strong coupling length dependence on wavelength and a high transmission for a 90° bend also make the proposed plasmonic waveguide promising for the realization of wavelength-selective components.
Highlights
Integrating the areas of nanoelectronic and photonic devices is hindered by the inherent diffraction limit of light energy supported in dielectric media
We study the coupling strength of a directional coupler and the bending loss of a 90° bend by completely examining the compactness and integration of the proposed symmetric HPW (SHPW), which is applicable for designing various photonic devices
The schematic of the proposed SHPW [Fig. 1(a)] consists of a cylinder metal (Ag) nanowire surrounded by low-index SiO2 and high-index Si covered by SiO2
Summary
Integrating the areas of nanoelectronic and photonic devices is hindered by the inherent diffraction limit of light energy supported in dielectric media. After the pioneering paper [11], the HPW concept has attracted much attention and is widely used to design diverse plasmonic components [12,13,14,15,16,17,18,19,20,21] These designs are mainly used for attaining deep subwavelength mode areas on the order of 10−2 (λ2/4) to 10−3 (λ2/4), where λ is vacuum wavelength; the propagation lengths are limited to tens to several hundreds of micrometers.
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