Finite element and perturbative study of buffered leaky planar waveguides

• Published in: Optics communications 2005-09, Vol.253 (1), p.99-108
• Main Authors: Uranus, H.P., Hoekstra, H.J.W.M., van Groesen, E.
• Format: Article
• Language: English
• Subjects: Applied sciences; Buffered leaky waveguide; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Finite element method; Integrated optics. Optical fibers and wave guides; Leakage loss; Leaky mode; Optical and optoelectronic circuits; Perturbation method; Waveguides, couplers, and arrays
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2005.04.053

The effects of the presence of a high-index medium in the proximity of planar waveguiding structures that makes up buffered leaky waveguides, were studied using a finite element method (FEM) leaky mode solver and a perturbation method. Various phenomena observed in the FEM results were interpreted through the approximate analytical expressions derived using the perturbation method. The effect of the buffer layer thickness, the high-index medium refractive index, and the quasi-confinement of the modal field were investigated. The results show that the perturbation due to the high-index medium can lead to either an increase or a decrease of the real part of the effective index, and that the leakage loss of a TE-polarized mode is not always lower than TM-polarized mode of the same order. It was found that if the refractive index of the high-index medium goes to infinity, a leaky-wave structure evolves into a guided-wave structure.