Triangular Shape Hybrid Metal-Insulator-Metal Plasmonic Waveguide for Low Propagation Loss at Deep Subwavelength

Abstract

The triangular shape based hybrid metal-insulator-metal plasmonic waveguide, to achieve the low propagation loss at deep-subwavelength, has been proposed, and analyzed for the optical properties of the fundamental mode, such as normalized effective mode area, propagation length, etc., at <inline-formula><tex-math notation="LaTeX">$1550{\rm{\ nm}}$</tex-math></inline-formula> of working wavelength. Due to the triangular type of high-index regions, the light is primarily confined at its tip-points, i.e., within the low-index materials. This type of waveguide structure can essentially provide the remarkably low propagation loss at deep subwavelength. The optical performance of fundamental hybrid mode is analyzed, by altering the waveguide dimensions, including the angle of triangular-shape high-index layer. Further, the investigation of mode character helps to understand the mode behavior of the proposed waveguide. The simulation results have established that the propagation length of fundamental hybrid mode of the presented waveguide can be achieved as &#x223C; 279.7 &#x03BC;m, with the normalized effective mode area of <inline-formula><tex-math notation="LaTeX">$\sim \ 0.4842$</tex-math></inline-formula>, at <inline-formula><tex-math notation="LaTeX">$w= 200\ nm$</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">${h_{si}} = \ 300\ nm$</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">${h_g} = \ 10\ nm$</tex-math></inline-formula>, and <inline-formula><tex-math notation="LaTeX">${h_m} = \ 100\ nm$</tex-math></inline-formula>; however, with other waveguide dimensions, <inline-formula><tex-math notation="LaTeX">${L_p}$</tex-math></inline-formula> has been achieved as, <inline-formula><tex-math notation="LaTeX">$ &gt; 700\ \mu m.$</tex-math></inline-formula> Further, the analysis on coupling length <inline-formula><tex-math notation="LaTeX">$( {{L_c}} ),$</tex-math></inline-formula> between the two nearby and similar type of the proposed waveguides, have been accomplished, and <inline-formula><tex-math notation="LaTeX">${L_c} &gt; 2500\ \mu m$</tex-math></inline-formula> has been attained for the waveguide separation, and width respectively of <inline-formula><tex-math notation="LaTeX">$800\ nm$</tex-math></inline-formula>, and <inline-formula><tex-math notation="LaTeX">$200\ nm$</tex-math></inline-formula>. Moreover, the phases of fabrication process, along with the tolerance issues in fabricating the tip-points of high-index regions, have been discussed for the proposed waveguide structure. The waveguide structure proposed in this work can be fundamentally effective for the proposal of various nano-photonic components, such as power splitter, directional coupler, etc.