Two-dimensional Slab Waveguides Research Articles

Asymptotic solutions of eigenmodes in slab waveguides terminated by perfectly matched layers

For numerical modeling of optical wave-guiding structures, perfectly matched layers (PMLs) are widely used to terminate the transverse variables of the waveguide. The PML modes are the eigenmodes of a waveguide terminated by PMLs, and they have found important applications in the mode matching method, the coupled mode theory, and so on. In this paper, we consider PML modes for two-dimensional slab waveguides. It is shown that the PML modes consist of perturbed propagating modes, perturbed leaky modes, and two infinite sequences of Berenger modes. High-order asymptotic solutions for the Berenger modes are derived using a systematic approach.

Simulation of optical waveguides by novel full-vectorial pseudospectral-based imaginary-distance beam propagation method

This work presents a novel full-vectorial imaginary-distance beam propagation method based on the multidomain pseudospectral scheme, for the first time, to study the modal characteristics of dielectric optical waveguides. The proposed method divides the transverse plane into several subdomains with uniform refractive indices, and expands the optical field in each subdomain in terms of a set of suitable basis functions. Accordingly, the complicated cross-coupling terms, which are required by the finite difference or finite element schemes, can be removed from the full-vectorial formulations. However, the coupling effect can be restored by matching the physical interface conditions. Moreover, to identify the higher-order modes, the residual traces of the preceding lower-order modes are subtracted from the calculated optical fields in each propagation step to suppress the rapid growth of the lower-order modes. Numerical examples of the two-dimensional slab waveguides demonstrate that the present approach yields a highly accurate propagation constant. When applied to three-dimensional rib waveguides the present scheme yields results that remarkably agree with the reliable values obtained from the modal transverse resonance method and finite element scheme.

Observation of Brillouin zone folding in photonic crystal slab waveguides possessing a superlattice pattern

The optical properties of superlattice photonic crystal (PC) patterns in two-dimensional slab waveguides were investigated using coupled-resonance angular dependent reflectivity measurements. Additional features were found in the superlattice PC spectra in comparison to that of the triangular lattice, indicating Brillouin zone folding (BZF) due to the larger unit cell and reduced symmetry of the superlattice. Calculated band structures corroborate these measurements and confirm the BZF effect which was shown to extract portions of the triangular lattice guided bands into the waveguide radiating regime, making the dielectric bands excitable by an out-of-plane source.

Leaky modes of slab waveguides-asymptotic solutions

Approximate analytic solutions of the leaky modes in two-dimensional slab waveguides are derived through an asymptotic analysis. General slab waveguides with three layers of possibly different refractive indexes are studied for both the transverse electric (TE) and transverse magnetic (TM) cases. The results are useful in the eigenmode expansion method, where the leaky modes appear if a perfectly matched layer (PML) is used to terminate the transverse directions of optical waveguides.

NUMERICAL ANALYSIS OF OPTICAL WAVEGUIDES BASED ON PERIODIC FOURIER TRANSFORM

Periodic Fourier transform is formally introduced to anal- yses of the electromagnetic wave propagation in optical waveguides. The transform make the field components periodic and they are then expanded in Fourier series without introducing an approximation of artificial periodic boundary. The proposed formulation is applied to two-dimensional slab waveguide structures, and the numerical results evaluate the validity and show some properties of convergence.

Transmission characteristics of dielectric-coated metallic waveguide for infrared transmission: Slab waveguide model

A metallic hollow waveguide with inner dielectric multilayers is proposed for the transmission of infrared light and its basic transmission characteristics are fully analyzed by using a two-dimensional slab waveguide model. The power loss in the waveguide is shown to be extremely reduced by coating dielectric layers properly. Simple loss formulas are also presented which consider absorptions of dielectric materials, and minimum possible losses are theoretically estimated. Finally, relations to bending losses in the waveguide are discussed.