The calculation of bending waveguide modes is essential to the design of Planar Lightwave Circuits (PLCs) and other waveguide-based photonic devices. Bending waveguides introduce shifts in the mode shape and bending losses which, as a function of the waveguide radius, determine the minimum bending radius as well as the minimum size of the PLC. We will use a simulated bend in FemSIM to calculate the bending mode.
As an example, we will compute the fundamental bending mode of a simple ridge waveguide shown here. It has a width of 1.4 μm and consists of an InGaAsP guiding layer (n= 3.39) and an InP cap layer and substrate (n = 3.17). The operating wavelength is 1.55 μm.