SPOT SIZE EXPANSION FOR IMPROVED OEIC-TO-FIBER COUPLING USING DIRECTIONAL-COUPLERS WITH 2D CONFINEMENT

In optical fibre applications, by using an intermediate multiguide dir ectional coupler section, this work has shown that the field profile o f the source laser used can be expanded to match that of the receiving optical fibre. The vector H-field finite element method has been empl oyed to determine the modal propagation constants and vector field pro files. An accurate calculation of the excited modal coefficients was a chieved by using the least squares boundary residual method, which sat isfies the continuity of the transverse field components more rigorous ly than through the use of the simple overlap integral approach.