Analysis of semiconductor rib waveguides: spectral index method

The authors present a new fast way, the spectral index method (SI), of modelling polarized modes in semiconductor rib waveguides. The spectral index method finds a simple solution in the rib using symmetric slab modes and links this with a Fourier transform of the solution below the rib. The field equations are solved exactly in all regions except actually on the base of the rib, where a variational principle is used to link the two exact solutions. The field distributions below the rib appear in the form of a known Fourier transform which can be readily inverted using a fast Fourier transform (FFT). In combination, the spectral index waveguide solver and an FFT routine to generate field profiles constitute an accurate and versatile tool for fast waveguide analysis