Radiation losses on discontinuities in integrated optical waveguides

A method to obtain the electromagnetic scattering properties of step discon tinuities between integrated optical waveguides is presented. The method in volves a new generalized scattering-matrix concept, together with the gener alized telegraph-equation formalism and the modal matching technique. Our m odel encloses the optical waveguides with perfectly conducting walls. Refle ction, transmission, and radiation coefficients can be obtained for step di scontinuities in monomode or multimode optical waveguides with arbitrary re fractive index profile functions. Furthermore, the method can be applied to any cascaded set of multiple discontinuities between planar or channel opt ical waveguides. In this way, segmented optical waveguides, optical wavegui de gratings, transitions, and tapers can be analyzed by modelization as mul tiple abrupt discontinuities. Excellent convergence and accuracy were obser ved finding the optical waveguide modes. Results on convergence and accurac y for effective indices, as well as for radiation losses for step discontin uities, are given and compared with those presented by other authors. (C) 1 999 Society of Photo-Optical instrumentation Engineers. [S0091-3286(99)0031 0-4].