The field of photonic integrated circuits (PICs) has attracted interest in recent years as they allow high device density while requiring only low operating power. The possibility of exploiting mode division multiplexing (MDM) in future optical communication networks is being investigated as a potential method for supporting the constantly increasing internet traffic demand . Mode converters are important components necessary to support on-chip processing of MDM signals and multiple approaches has been followed in realizing such devices , . Topology optimization (TO)  is a powerful inverse design tool which has experimentally proven to deliver robust designs with controllable bandwidth and low loss , . Here it is shown how TO has been used to obtain a small footprint, low-loss, broad-band design for mode conversion between the transverse electric fundamental even (TE0) mode and the first higher order odd mode (TE1) in a photonic wire. The design is to be fabricated in silicon-on-insulator (SOI) material, and previous work has shown excellent correspondence between simulations and experimental results for 3D TO .
Proceeding of IEEE Photonics Conference, paper MH2.2 (invited) (2015).