Numerical and semi-analytical techniques widely used to model the complicated structure of the radiation field excited on sharp and smooth discontinuities of a dielectric slab are reviewed. Comparative analysis of the radiation field modelling by the fast Fourier transformation-beam propagation method (FFT-BPM) and the finite difference (FD)-BPM is presented. Propagation of a higher-order mode through the cut-off cross-section of smooth and sharp discontinuities is simulated numerically by the FD-BPM, the total field is analysed using the leaky mode approach. [References: 26]
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