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We apply a design method based on topology optimization technique to optical waveguide devices. In our approach, after a refractive index profile in a design region is automatically generated using a topology optimization method, the obtained structure is redefined using primitive geometries with some design parameters and those parameters are optimized by a sequential linear programming. As numerical examples, we demonstrate how the method can be used for 90 bends and T-branching waveguides with arbitrary splitting ratio., application/pdf

A new arbitrarily oriented perfectly matched layer (PML) is developed for truncating finite element meshes in waveguiding problems. The PML can have any orientation with flexible parameters such as stretching variables and thicknesses. It is based on the PMLs stretched step-by-step along each normal direction of their surface. The formulation is easily adapted within the finite element method frameworks, providing good simulation results., application/pdf

A new formulation of the finite-element method to analyze nonreciprocal waveguides in magneto-photonic crystals (MPCs) is proposed. Accurate solutions of light propagations for two different directions are obtained by the asymmetrical input condition. As numerical examples, the performance of a waveguide-type optical isolator in MPCs designed by the eigenmode analyses is confirmed by using this method. Subsequently, an effective way to enhance the nonreciprocity of the optical isolator is shown., application/pdf

A high-performance absorbing boundary condition is newly developed for the reduction of spurious reflections in photonic crystal (PC) waveguide simulations. The PC waveguide is terminated with a perfectly matched layer (PML) in which the original PC structure remains as is. This PC-based PML works well, compared to a conventional PML, which acts as a homogeneous absorbing medium, simulating a semi-infinite free space and to a distributed-Bragg-reflector waveguide, which was recently developed to reduce reflections from PC waveguide ends, improving a wavenumber matching condition for PC waveguide modes.

A time-domain beam propagation method (BPM) based on the finite-element scheme is described for the analysis of reflections of both transverse electric and transverse magnetic polariaed pulses in wavegniding structures containing arbitrarily shaped discontinuities. In order to avoid nonphysical reflections from the computational window edges, the perfectly matched layer boundarv condition is introduced. The mesent algorithm usine the Pade approximation is, to our knowle-dge, the Krst time-domain beam propagation method which can treat wide-band optical pulses. After validating this method for an optical grating with modulated refrative indexes, various photonic crystal circuit components are simulated.

A unified approach using curvilinear hybrid edge/nodal elements with triangular shape is, for the first time, described for the study of guided-wave problems. Not only the lowest order (fundamental) but the higher order elements are systematically constructed. The advantage of curvilinear elements lies in the fact that they can model curved boundaries with more accuracy and lesser number of degrees of freedom than rectilinear elements. The vector basis functions derived here are also applicable to rectilinear cases. To show the validity and usefulness of the present approach, computed results are illustrated for rib waveguides with straight boundaries and circular waveguides with large refractive-index differences.