Inverse Effective Index Method for Two-Dimensional Simulations of Photonic Components

The representation of three-dimensional integrated photonic structures in two-dimensional designs has been investigated through finite element analysis using COMSOL Multiphysics. The accuracy of the effective index method for various waveguide designs is studied. An alternative to the effective index method, here named the inverse effective index method, is derived in this paper. The results indicate that the commonly used effective index method has a deviation in propagation constant up to 17%, where the error is largest for low-confinement factor waveguides. The inverse effective index method vastly reduces this error to < 0.01% for low confinement-factor geometries. This enables an accurate simulation in two-dimensions while retaining the waveguiding properties of the third dimension. As with the effective index method, the inverse effective index method does not require proprietary software.