Efficient algorithm for scalar to full-vectorial mode conversion in optical waveguides

Optical waveguides, serving as the fundamental structure to manipulate light propagation, have eigenmodes and eigenvalues. Full-vectorial modes contain full-scale modal information, particularly for waveguides with strong index contrast. Conventional algorithms to compute full-vectorial eigenmodes and eigenvalues usually require time-consuming eigenvalue computation, which becomes computationally intensive in case the waveguide cross-section becomes large. In this work, a full-vectorial mode computation algorithm is proposed based on adiabatic perturbation theory. Starting from scalar modes computed for the same optical waveguide structure, one is able to include the impact of the index profile gradient and obtain the full-vectorial mode profiles and propagation constants by the adiabatic perturbation theory, which does not need further eigenvalue computation. The method is applied to optical waveguides with weak and strong index contrast. High accuracy is observed with ultra-low computational cost.