Traditional fabrication techniques have struggled to deliver compact, low-loss solutions that can adapt to the diverse core geometries of modern multi-core optical fibers (MCFs). The researchers tackled this challenge using Two-Photon Polymerization (2PP) on a Nanoscribe Quantum X system. The result is a fully 3D-printed optical splitter that integrates multiple optical functions into a single microstructure. This high level of integration reduces system size and complexity while enabling custom coupling geometries, selective core addressing, and direct on-fiber printing.
Creating 3D microdevices for fiber systems
The newly developed 1×4 splitter was designed to achieve compactness, optical precision, and compatibility with existing fiber systems. Its structure includes a triangular multimode interference coupler, S-bends for waveguide routing, and adiabatic tapers to match fiber mode profiles. These features were integrated into a 3D model optimized for a footprint of just 180 µm length. The component was fabricated using Two-Photon Polymerization in Nanoscribe’s IP-Dip resin, which supports high optical clarity and sub-micron resolution. The printed device enables selective light routing into four specific cores of a multi-core fiber, ideal for use in fiber-based sensors, optical networks, or lab-on-fiber systems.
Enabling freeform optics with sub-micron detail
Conventional fabrication methods such as lithography or fiber splicing often fall short when it comes to fabricating miniature, freeform 3D photonic components. In contrast, Two-Photon Polymerization enables the direct printing of smooth waveguide transitions, tight bends, and highly aligned structures - all in a single fabrication step. Using Nanoscribe’s Quantum X shape, a high-resolution 3D printer based on 2PP, the researchers produced the splitter directly in polymer. The ability to directly print freeform 3D structures with submicron accuracy was critical for the performance of the optical splitter. The splitter allows these complex fibers to be connected directly to a single-core interrogator without the need for bulky and alignment-sensitive fan-out modules.
Investigating functionality across fiber cores
After fabrication, the optical splitters were tested using butt-coupled single-core and multi-core fibers to assess transmission performance. The researchers characterized insertion loss, wavelength dependence, and polarization behavior across the C- and L-bands. The central output core consistently showed the lowest insertion loss, while outer cores demonstrated higher losses due to S-bend geometries. On average, the insertion loss per channel was around -3 dB. The devices also demonstrated low polarization-dependent loss, confirming the effectiveness of the design and the manufacturing precision of the 3D printing process.
Improving fiber coupling for photonic applications
This 3D-printed splitter addresses the rising demand for compact, customized photonic components in fields like telecommunications, quantum technologies, and medical diagnostics. In real-time shape sensing for robotic instruments or endoscopes, for example, the multi-core fibers are used to detect fine movements and deformations inside the human body. In telecom applications, it supports spatial division multiplexing for higher bandwidth. It also opens new possibilities in quantum communication, where precisely routing light into selected cores is critical for multiplexing and secure signal separation.
