Design of Power-Splitter With Selectable Splitting-Ratio Using Angled and Cascaded MMI-Coupler

A concept of power splitter with selectable splitting-ratios is proposed based on two multimode interference (MMI) sections connected by a phase-shifting region, in which phase-matching conditions can be fulfilled by using a simple angled section or alternatively using matched phase-shifters. The design example of an asymmetrical splitter (10 : 90) is optimized by using the transfer matrix method and three-dimensional full-vectorial beam propagation method. The numerical results reveal that a simple 1.2° angled section can yield a 10 : 90 splitter with an insertion loss of 0.74 dB and a total length of 192 μm. It is also shown that, for the cascaded MMI couplers based splitter, a more compact length of 58 μm with a lower insertion loss of 0.41 dB can be achieved. The fabrication tolerances are also investigated for the proposed asymmetrical power splitter