Improved tolerance in polarisation splitters

A new design for a passive polarisation splitter is presented. The device consists of a di-rectional coupler with tapered waveguides. The modal birefringence for 3rd order modes for TE and TM polarisations is employed to selectively couple one polarisation. Tapered waveguides in combination with a tapered coupling region are used to create more tol-erant designs. Because of the tapered region, the coupling condition is met for a larger width span, compatible with standard optical lithography. BPM simulations show a width deviation of 150 nm still yields a splitting better than 95%