Optimized Design Procedure for Low-cost Grating-couplers in Photonics-packaging

A specific and robust design-routine for the optimization of Grating-Couplers (GCs) has been created resorting to the well-known Particle Swarm Optimization (PSO) algorithm implemented inside a commercial software based on the Finite Difference Time Domain (FDTD) method. The combination of the PSO algorithm and the FDTD method can represent a powerful tool for optimizing several GC structures through a well-defined model that governs the GC performances as a function of their structural parameters. The final output of our design-routine is a file, which can be directly imported inside lithographic control interfaces for the writing steps. To validate our design-routine, a comparison between our results and two `gold' structures, reported in literature, is proposed. As an application, the optimization of a GC for planar Fiber-to-GC coupling, which is interesting from a photonics packaging prospective, is provided. The aim is to show the recovering of the 0.6 dB higher insertion-losses related to this scheme respect to the bulkier vertical Fiber-to-GC geometry used as the standard-configuration for grating-coupling.