Efficient Modelling of 3D-Printed Freeform Waveguides by a Dedicated Beam-Propagation Method (BPM) Based on Transformation Optics

An efficient numerical algorithm is developed to model wave propagation in 3D-printed freeform waveguides, so-called photonic wire bonds (PWBs). The method utilizes transformation-optics (TO) in combination with curvilinear meshing to transform the original 3D-freeform PWB into a straight waveguide with anisotropic material properties. This waveguide is then modeled using an anisotropic full-vectorial beam propagation method (BPM). We demonstrate the viability of our TO-BPM algorithm and benchmark its performance against a finite-difference-time-domain (FDTD) method. Our approach shows a 600-fold reduction of the computation time in combination with a mean percentage error of 3.2% in power transmission simulation relative to the FDTD.