The design of triple rib waveguide couplers by the discrete spectral indexmethod

The operations of three-guide couplers are usually controlled by the width and refractive index of the guides. However, when rib waveguides are used i n three-guide couplers and power dividers, we propose to use the dimensions of the ribs as the governing parameters instead. Formulating a new transce ndental equation using the discrete spectral index (DSI) method, triple rib waveguide couplers are accurately analyzed for the first time, The new acc urate and fast analysis of triple rib waveguides shows that the propagation constants of the various modes are dominantly controlled by the height of the middle rib. A systematic and simple procedure is consequently introduce d to design quasi-transverse electric (TE) polarized triple rib waveguide c ouplers, which ensures maximum power transfer from one outermost guide to t he other outermost guide, For triple rib power dividers, the height of the middle rib is found to control the amount of power that can be transferred from the excited middle rib waveguide to the two outer rib waveguides, Maxi mum power division is achieved when the three ribs of the waveguide are ide ntical.