Eigenmode analysis of a light-guiding metal line loaded on a dielectric substrate using the imaginary-distance beam-propagation method

Abstract

Abstract-Fundamental characteristics of a light-guiding metal line are revealed and discussed through the eigenmode analysis using the three-dimensional (3-D) imaginary-distance beam-propagation method (ID-BPM) based on the alternating-direction implicit scheme. For the present ID-BPM, the multiplication factor of the eigenmode is derived and the paper described how the present method works in the ID procedure. An efficient absorbing boundary condition is described, which is suitable for the eigenmode analysis using the ID-BPM. After confirming the effectiveness of the present method, the characteristics of the light-guiding line composed of a metal (Au) with a finite width and thickness on a substrate (SiO 2 ) are investigated. Numerical results for a metal thickness of 0.2 m show that the effective index and the propagation loss decrease as the metal width is reduced. It is shown that not only the higher order modes but also the first mode has a cutoff metal width. Near the cutoff width, the propagation loss of the first mode ( 10 dB/mm at a wavelength of 1.55 m) is less than those of the higher order modes. Finally, in order to reduce the propagation loss, a dielectric core was added under the metal line.Index Terms-Beam-propagation method (BPM), eigenmode analysis, imaginary-distance (ID) procedure, light-guiding metal line, surface plasmon-polaritons.

A Branch-Type TE/TM Wave Splitter Using a Light-Guiding Metal Line

“…The sampling widths are fixed to be ∆x = 0.05 µm and ∆y = ∆z = 0.02 µm. The perfectly matched layer is placed at the edge of the computational region [19], [23].…”

“…For Ag, the calculation shows that the loss of the SPP mode asymptotically decreases as the metal thickness t is increased. This is because the field becomes less confined to the metal with an increase in the thickness [19]. A further increase in the thickness leads to the fact that the loss for t > 0.1 µm is almost constant.…”

“…Our idea comes from the fact that the strong field confinement of the surface plasmon-polariton (SPP) mode [17]- [19] permits an increase in a branching angle while maintaining a reasonable extinction ratio. This means that the splitter has the possibility of operating over a wide range of wavelengths with a short device length, although the TM wave inherently incurs some loss due to the field absorption in the metal.…”

Coupled Waveguide Polarization Splitter With Slightly Different Core Widths

“…The sampling widths are fixed to be and . The perfectly matched layer is imposed at the computational window edge [23], [24].…”

Leakage loss and phase variation of a buried directional coupler on a silicon substrate

“…This is because the amplification factor cannot be strictly determined due to the splitting error in the ADI process [11]. It is known that the multifrontal method based on the sparse LU decomposition technique is an efficient direct method, which can be used for the case where an iterative method is unstable, although the more memory is required than the iterative method.…”