Ultra-Low-Loss Fiber-to-Chip Coupling for Next-Generation Photonic and Quantum Systems

Photonic integrated circuits are becoming a cornerstone technology for future communication, computing, sensing, and quantum systems. As photonic devices advance in performance and complexity, and emerging applications demand ever tighter loss budgets, the optical interface between fibers and photonic chips is becoming a critical bottleneck in overall system performance. Recent advances in photonic packaging have significantly improved coupling efficiency, yet fiber-to-chip interfaces continue to pose major challenges for next-generation applications, particularly in quantum technologies where every lost photon directly impacts functionality and scalability. As highlighted by Weninger et al. in their review paper, simultaneously achieving low optical loss, manufacturability, alignment tolerance, and scalability remains one of the key challenges in photonic packaging.

Despite substantial progress in edge couplers, inverse tapers, grating couplers, and hybrid integration approaches, a significant gap remains between state-of-the-art laboratory demonstrations and solutions that can be deployed reliably in practical systems. Addressing this gap requires advances across the full photonic integration chain, encompassing interface design, tolerance- and reliability-aware optimization, scalable fabrication and packaging technologies, and system-level co-design.

This PhD aims to develop ultra-low-loss, robust, and manufacturable fiber-to-chip interfaces targeting coupling losses below 0.1 dB per interface. The research will investigate novel coupling architectures that combine advanced photonic design, micro-optical engineering, and innovative packaging concepts to maximize coupling efficiency while maintaining alignment tolerance, fabrication robustness, and environmental stability. The work will combine optical simulation and tolerance analysis with the experimental realization of demonstrator devices on representative photonic integrated circuit platforms. Comprehensive optical characterization and reliability testing will be used to evaluate performance under realistic operating conditions. By establishing new design methodologies and integration approaches for ultra-low-loss optical interfaces, this research seeks to remove a key barrier to the widespread adoption of advanced photonic systems and enable future optical I/O, co-packaged optics, quantum communication, and quantum sensing technologies.

Reference:
Weninger, D. et al., Advances in Waveguide-to-Waveguide Couplers for 3D Integrated Photonic Packaging, Light: Science & Applications, 2026.