Inverse Design of 3D-Printed Photonic Wire Bond Couplers - Benchmarking Different Optimization Strategies

3D nanoprinting enables the fabrication of photonic freeform structures with critical features on the sub-micrometer scale and a significant spatial extent. This ability can be exploited to print photonic wire bonds (PWB) that optically interconnect different components in photonic integrated circuits (PICs). However, efficient and compact couplers between PWBs and other PIC components remain a prime challenge. Despite the immense design flexibility afforded by 3D nanoprinting, the absence of suitable design methodologies has hindered the full exploitation of its potential. Here, this challenge is addressed by, exemplarily, focusing on 3D nanoprinted couplers between a single-mode fiber and a PWB. Using topology optimization enhanced by a novel parameterization scheme, ultra-short, fabrication-robust, and highly efficient broadband couplers are designed. Our results are benchmarked against a state-of-the-art global Bayesian optimization approach, providing comparative insights into the advantages and limitations of these methods. These findings pave the way for broader application of 3D nanoprinting in designing next-generation photonic components.