Collaborators at the University of Delaware in Newark and the US Air Force Research Laboratory at Hanscom Air Force Base, Mass., have modeled and analyzed the performance of 2-D directional coupler switches based on silicon pillars in air and on perforated silicon slab photonic crystals. The proposed 2 X 2 channel-waveguide design controls switching by inducing optical loss between two proximate parallel line defects in either a dielectric post or perforated slab matrix.In the Oct. 7 issue of Optics Express, the researchers describe 1.55-µm finite difference time-domain analysis of their devices to predict low insertion loss and crosstalk below -23 dB in both switching states. They plan to improve the design to enable complete switching with lower conductance.