Optimal Design of Photonic Devices Using Coordinate Transformation Finite Element Beam Propagation Method

In order to calculate photonic devices with slowly varying structural variation along propagation direction, we develop finite element beam propagation method (FE-BPM) with coordinate transformation. In this approach, converting a longitudinally varying waveguide into equivalent straight waveguide, cumbersome processes in FE-BPM, such as mesh updating process, is avoided. We employ this simulation technique in shape optimization of photonic devices and show a design example of mode converter.