Phase-matched rectangular magnetooptic waveguides for applications in integrated optics isolators:: numerical assessment

Phase matching between the fundamental TE and TM modes is an essential condition for complete polarization rotation in magnetooptic waveguides with longitudinally directed magnetization. This condition can be satisfied with embedded square waveguides or with raised strip waveguides, provided that the core dimensions are suitably chosen. Based on coupled mode theory for the vectorial modes of rectangular isotropic waveguides, we numerically simulate the performance of such devices in an experimental isolator setup, including birefringence and optical absorption. Fabrication tolerances with respect to all relevant parameters can be evaluated by simple perturbational expressions. Numerical verification shows that these formulas are accurate enough for practical purposes. The tolerances qualify the traditional polarization rotator setup as competitive to recent proposals for integrated optical isolators based on nonreciprocal interferometry. (C) 1998 Elsevier Science B.V. All rights reserved.