A Bidirectional Propagation Algorithm for Large Refractive Index Steps and Systems of Waveguides Based on the Mode Matching Method

An accurate and fast propagation method for dielectric passive and active waveguides is a useful tool for OEIC design. The propagation constant, the intensity distribution, optical transmission/ reflection and the coupling efficiency characterize a device and can be calculated with several methods. However, large refractive index steps both in the propagation direction (gratings, BUTT-coupling), as well as in the transverse direction (multi waveguide structure, vertical coupler) lie above the common calculation limits of most optical modelling methods. A standard Transfer-Matrix-Method (TFM) 1 takes into account one forward and one backward travelling wave so that the reflection and transmission characteristics can be obtained even for large refractive index steps and for any quantity of sections in the propagation direction. However, the standard TFM assumes lateral homogeneous sections and hence neglects the lateral structure, which is essential for the function of many devices (e.g. couplers). The method presented here combines the advantages of an extended Transfer-Matrix-Method 2 for the propagation of a set of travelling waves and the accurate handling of Maxwell's boundary condition by the Mode-Matching-Method (MM-Method)3. Neither paraxial approximations nor restriction on the polarization (TE or TM modes) are applied.
This Article is from 'Integrated Photonics Research'. Volume 10, AD-A255 423, p134-135.