Crosstalk reduction in intersecting rib waveguides

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 two percent for crossing angles greater than four degrees. A simple modification to the waveguide shape at the X-crossing region was found to reduce the crosstalk for crossing angles between four and ten degrees. The crosstalk to throughput ratio is reduced by up to a factor of nine while the throughput is reduced by, at most, a few percent. In device structures that combine X-crossings with curved waveguide sections this permits greater design flexibility and improved overall loss and crosstalk performance.