Design and optimization of optical interconnect using vertically grown periodic III-V nanowires on silicon

In this work, we study light propagation and coupling in a system of III-V nanowire array arranged vertically on a planer silicon waveguide, using two-dimensional (2D) and three-dimensional (3D) Finite-Difference Time-Domain (FDTD) techniques. We have considered waveguide comprising GaAs and GaN nanowires and shown that efficient light coupling can be achieved by optimizing the lateral and longitudinal dimensions, heights and spacings of the nanowires. The results of 2D analysis show that 82% light can be extracted from a waveguide of GaAs nanowire array, whereas the value is 40% for GaN nanowire array because of the lower refractive index of this material system. In the presence of a coherent source, the efficiency of light coupling from nanowire array to waveguide becomes 80% for GaAs and 57% for GaN nanowires. We also find that for efficient light coupling in both directions, less amount of material will be required in GaAs-based system due to the smaller-diameter-nanowire requirement for GaAs than for GaN. In order to study a more practical system, the performance characteristics are further analyzed using 3D FDTD simulation technique and the results are in good agreement with the results of 2D analysis.