Full-vectorial Finite-difference Method Research Articles

Simple and effective calculation of modal properties of bent slot waveguides

Three-dimensional bent slot waveguides are analyzed using a combined effective-index method/modified transfer-matrix method. The effective refractive index and bending loss of the guided mode can be acquired. The results closely match those calculated by the full-vectorial finite-difference method. This method also enables the calculation of field distribution, useful in estimating power confined in the narrow slot, and can handle asymmetric bent slot waveguides, bent multiple-slot waveguides, and hybrid bent slot waveguides. This approach has advantages of simplicity, versatility, and time-saving calculation, which are beneficial for the quick design of devices using bent slot waveguides.

Characteristic analysis of nanosilicon rectangular waveguides for planar light-wave circuits of high integration

When a full-vectorial finite-difference method is used, rectangular Si waveguides can be characterized for planar light-wave circuits of high integration. The single-mode condition for a rectangular Si waveguide is obtained first. The birefringence, which can be adjusted by modifying the thickness of the cladding layer, is also studied. For a nano-Si rectangular waveguide the pure bending loss is very small even for an ultrasmall bending radius (e.g., a few micrometers), and the transition loss becomes dominant. The width and height are optimized to minimize the bending radius for the requirement that the bending loss is smaller than 0.1 dB. Finally the coupling between two parallel straight waveguides is analyzed, and it is shown that there is an optimal width for the maximal coupling length.

Efficient simulation of subwavelength plasmonic waveguides using implicitly restarted Arnoldi

In this paper, we present a full-vector finite difference method to solve for optical modes in one and two dimensional subwavelength plasmonic waveguides. We have used the Implicitly Restarted Arnoldi method to directly calculate the propagation constants of the dominant modes. The method has low computational complexity and can be applied to accurately model complex geometries and structures with fast-varying field profiles. When applied to solve for purely bounded modes, our method automatically separates evanescent and low-loss guided modes.

Numerical analysis of Bragg fibers using a compact 1D finite-difference frequency-domain method

A simple full vectorial finite-difference frequency-domain method is presented for dispersion and loss analysis of Bragg fibers. In both axial and azimuthal directions, the derivatives of the Maxwell’s equations are calculated analytically, and the solution of Maxwell’s equations is reduced to a 1D eigenvalue problem. Standard step-index and graded-index fibers with parabolic-index cores are analyzed to verify the validity of this method to round symmetric fibers with arbitrary index profiles. Numerical results on the mode propagation characteristics of Bragg fibers are found to agree very well with those obtained by transfer matrix method and Chew’s method.

Photonic band structures for surface waves on structured metal surfaces

Photonic band structures of surface modes on structured metal surfaces with periodic holes in them are obtained using the full-vectorial finite-difference time-domain method. Surface modes do exist for almost all investigated lattice types with any hole size, shape and depth. The results for a square lattice of wax-filled box holes in brass are also in very good agreement with the experimental results. We also show that, for structured surfaces with holes of finite depth, the holes might act as cavities. Thus there exist propagating coupled cavity modes with low group velocity, confined at the surface and decaying exponentially into the dielectric above.

Research on the effects of air hole shape on the properties of microstructured optical fibers

We numerically analyze and compare the mode and disper- sion properties of three different microstructured optical fibers with the same square array of different-shaped air holes: rhombic, square, and circular. We use a full vectorial finite-difference method. The analysis shows that the properties of microstructured optical fibers depend on the hole area, hole shape, and wavelength to different extents. The effects of air hole shapes on the properties of microstructured optical fibers can be treated as the perturbations for sufficiently small air filling factors. For larger air filling factors the properties of microstructured optical fibers are clearly affected by the air hole shape. This dependence is useful for understanding the properties of microstructured optical fibers. © 2004