Abstract

Recently, there has been increased interest in the analysis of passive polarization converters made with longitudinally-periodic structures owing their great polarization conversion efficiency. Three kinds of passive polarization converters made with periodic structures are presently reported in the literature: asymmetric loading section converters, tilted waveguiding section converters and asymmetric angled facet section converters. The most promising version so far is the angled facet converter recently proposed by van der To1 et al [ 1,2]. This polarization converter contains a series of N waveguide sections with right-asymmetric (RAS) and left-asymmetric (LAS) cross-sections with angled facets. Simplified structure of RAS and LAS cross-sections with angled facet are shown in Fig. 1. For any converters made of longitudinally-periodic structures, the main factors limiting the performance of the devices are the losses which occur at the junction between the neighboring sections and the difficulty of fabricating the multi-section devices. In this paper, using a vectorial finite-element propagation method to model angled facet converters, it is shown that polarization rotation effects in such devices can be maximized with an appropriate choice of the facet angle a and the base rib width w. Optimization of structure design achieves a device free of longitudinally-periodic structure with a very short converting length and low losses.

© 1996 Optical Society of America