New fast Fourier transform and finite‐element approaches to the calculation of multiple‐stripe‐geometry laser modes

We have developed a new method, based on the split‐step fast Fourier transform algorithm, for calculating the modes of a general graded‐index active waveguiding structure and demonstrate that the method can be applied to the periodic part of the Bloch function and hence to a strictly periodic multiple‐stripe‐geometry laser. We also develop a second approach involving the finite‐element method.