Intersecting rib waveguide structures with reduced crosstalk

A numerical study of the throughput and crosstalk in intersecting semiconductor rib waveguides was carried out using the beam propagation method. The fraction of the optical power that couples out of one input waveguide and into the crossed waveguide falls to below 3% for crossing angles greater than 4°. Two simple modifications to the waveguide shape at the X-crossing region were found to reduce the crosstalk for crossing angles between 4° and 10° such that the crosstalk to throughput ratio may be reduced by up to a factor of 100 while the throughput is reduced by, at most, a few percent. In device structures that combine X-crossings with curved waveguide sections our results permit greater design flexibility and improved overall loss and crosstalk performance.