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Advances in silicon photonics motivate the consideration of on-chip switch fabrics that combine switch elements into larger port-count switches. A major challenge is the large number of inter-stage waveguide crossovers. A novel freespace architecture utilising micro-lenses, capable of near zero insertion loss and crosstalk, is described and its principles of operation explained. The architecture is mapped to a planar implementation by the substitution of propagation in a slab-waveguide for free-space propagation and Luneburg lenses for the micro-lenses. Simulations show the careful approximation of the graded index of the Luneburg lens by a metamaterial introduces minimal additional crosstalk.