Optimization of optical wide band 3-dB MMI splitter with graded-index side diffusions

Abstract

The design of a 3-dB multimode-inter$erencebased symmetrical optical splitter for realization by ion exchange on glass substrates is optimized for wide band peformance taking the graded-index side diffusions into consideration. The depth of diffusion and width of the multimode waveguide section for best coupler performance are determined based on a modified model of ion-e.xchanged waveguides which takes into account the effective index grading in the lateral direction due to the finite width of the waveguide and the presence of side diffusions. The performance of the devices is simulated using the beam propagation method and compared to that of a conventional step-index design. Couplers with larger bandwidths are obtained using optimized designs. Index Terms 3-dB symmetrical optical splitter, multimodeinterference, wide band performance, ion exchange on glass, graded-index side diffusions.