Photonic integrated circuits (PICs) are reshaping fields such as high-speed communications, quantum technologies, and neuromorphic computing by offering unprecedented bandwidth, ultra-low latency, and superior energy efficiency compared with conventional electronic chips. Fabricated with lithographic techniques similar to those used for electronic chips, PICs integrate essential optical components like waveguides, modulators, and detectors on a single platform to guide and process light with high precision and stability.
Yet optical interfacing remains one major bottleneck: Coupling light in and out of the chip for data transfer typically requires fibers positioned with micrometer precision relative to narrowband grating couplers. Even state-of-the-art fiber-array-to-chip coupling still relies predominantly on active alignment, a process that remains time-consuming, costly, and difficult to scale in production environments.
Researchers at Heidelberg University have now addressed this challenge with a scalable plug-and-play fiber-to-chip connector fabricated by aligned high-precision 3D microprinting. The new approach enables self-aligned, broadband and low-loss optical coupling, replacing complex alignment setups with a simple insertion-locked connection.
Integrated optical and mechanical interface
The researchers developed a novel packaging concept that uses additive manufacturing to achieve optical coupling and mechanical alignment. Using multi-fiber termination push-on fiber arrays (MTP) with standardized alignment pinholes, the team 3D-printed the matching counterpart directly onto the photonic chip by Two-Photon Polymerization (2PP). Coupling is realized via total internal reflection (TIR) couplers that focus and redirect light from the on-chip waveguides into the fibers providing broadband, and low-loss coupling.
The concept was validated on a 16-input-port photonic tensor core for neuromorphic computing, demonstrating self-aligned fiber coupling with sub-dB insertion losses and nearly wavelength-independent performance. By combining a mechanical interlocking mechanism with optical coupling, the team achieved a scalable and manufacturing-ready connector design – a significant step toward alignment-free packaging for large-scale PIC systems.
Scalable packaging solution for photonic integration
The new connector concept directly addresses a central challenge in photonic integrated circuit (PIC) packaging, achieving broadband, low-loss, and scalable optical interfacing. By eliminating active alignment, it enables automated, reproducible, and cost-efficient manufacturing, paving the way for volume production of advanced PIC-based systems.
Fully compatible with hybrid electronic–photonic integration, this approach supports modular and reconfigurable architectures required for quantum computing platforms, neuromorphic processors, and optical sensing systems. As a mass-manufacturable, passive packaging solution, it marks an important step toward practical large-scale deployment of next-generation photonic technologies in communications and computing.
Driving results with aligned high-precision 3D printing
Fabricating the low-loss, broadband, plug-and-play connector required meeting two key demands: mechanically stable alignment structures and a transparent, infrared-compatible material for optical coupling. These challenges were addressed with the Quantum X align system, whose high-precision Direct Laser Writing (DLW) process enables high-resolution 3D printing with nanometer-level alignment accuracy across different feature scales.
In a first DLW step focusing total internal reflection (TIR) couplers, each about 30 µm in height, were printed directly on the photonic chip. Using the Small Feature Print Set allows the fabrication of sub-micrometer optical structures in IP-Dip2, a transparent, infrared-compatible resin. With automatic marker-based alignment, the couplers were precisely positioned relative to the on-chip waveguides, while Two-Photon Grayscale Lithography (2GL®) ensured excellent optical performance by producing each coupler with smooth, accurately shaped surfaces in less than one minute.
