Researchers have built a microscopic 3D-printed optical device that funnels light from 37 separate multimode semiconductor lasers into a single optical fiber, merging 222 distinct spatial modes; the team reports low coupling loss in peer-reviewed measurements. The device, called a multimode photonic lantern, is described by the researchers as a step beyond conventional lanterns that typically use single-mode inputs, because it combines many multimode sources in one structure at this scale. The result is a compact structure smaller than a human hair’s width that could reshape how fiber-optic networks, laser systems, and satellite communications handle growing data demands.
What the Photonic Lantern Actually Does
A photonic lantern is a tapered waveguide structure that converts light traveling through many separate optical paths into a single multimode output, or vice versa. Traditional versions perform mode conversion between arrays of single-mode fibers and one multimode waveguide, a technique central to space-division multiplexing in telecommunications. The concept has been explored for over a decade, but scaling these devices to handle large numbers of modes while keeping signal losses low has remained a persistent engineering challenge.
The new device breaks from that convention. Instead of single-mode inputs, it accepts light from vertical-cavity surface-emitting lasers, or VCSELs, each of which already carries six spatial modes. By coupling 37 such lasers through a single lantern structure, the total mode count reaches 222, a figure far beyond what earlier designs could manage. This distinction matters because VCSELs are widely used in short-reach optical links and are designed for cost- and energy-efficient operation. A practical way to combine dozens of them into one fiber output could multiply the power and bandwidth of existing short-reach optical links without expensive coherent laser sources.
Fabrication Through 3D Nanoprinting
The team fabricated the lantern using direct laser writing and two-photon polymerization, a form of 3D nanoprinting that builds structures layer by layer at the microscale. Earlier work demonstrated that free-standing microscale photonic lanterns could be produced this way, establishing the basic feasibility of printing low-loss optical components small enough to sit on a fiber tip. The new study extends that approach to far more complex geometries, routing 37 separate input waveguides into a smooth taper that terminates at a standard multimode fiber.
The target fiber has a 50 micrometer core and a numerical aperture of 0.22, parameters that match widely deployed step-index multimode fiber used in short-distance data links. By printing the lantern directly onto the fiber endface, the researchers eliminate the delicate manual alignment steps that have historically limited photonic lantern production to small-batch laboratory demonstrations. The researchers describe the approach as potentially fast to fabricate and compatible with scalable production, because it avoids custom glass drawing or splicing; however, the study focuses on laboratory demonstrations rather than manufacturing deployment.
Loss Numbers That Challenge Conventional Limits
Signal loss is the critical metric for any optical coupler. Light that fails to transfer from input to output becomes wasted heat and degrades system performance. The peer-reviewed results, published in Nature Communications, report low coupling loss for both devices; the paper reports values of −0.6 dB for the 19-source device and −0.8 dB for the 37-source version (as defined by the authors’ measurement convention). Because the paper reports these values using its own sign convention, the key takeaway is that the measured coupling loss is small for a device combining dozens of multimode sources; readers should refer to the study’s definitions and setup for an apples-to-apples efficiency comparison.
These numbers deserve scrutiny. Most prior attempts at scaling photonic lanterns to higher modal counts ran into rapidly increasing losses because small fabrication errors compound across more waveguide transitions. The fact that losses grew by only 0.2 dB when jumping from 19 to 37 inputs suggests the 3D-printing approach handles geometric complexity better than traditional fiber-drawing methods. If the trend holds at even larger scales, it would open the door to lanterns with hundreds of inputs, though the authors have not yet demonstrated devices beyond 37 sources.
Why VCSELs Change the Equation
Most previous photonic lantern research focused on single-mode fiber inputs, which carry one spatial mode each. That approach works well for long-haul telecom, where single-mode fiber dominates. But the explosion of short-reach optical interconnects inside data centers runs on VCSELs paired with multimode fiber, a combination chosen for its low cost and ease of assembly. Bridging the gap between multimode VCSEL arrays and high-capacity fiber outputs has been an open problem.
The researchers’ multimode photonic lantern addresses this by treating each VCSEL’s multi-mode output as a native input rather than trying to strip it down to a single mode first. That design choice preserves the full brightness of each laser and avoids the lossy mode-filtering step that earlier hybrid schemes required. In the reported demonstrations, the research team showed configurations with 7, 19, and 37 VCSEL inputs to illustrate how the architecture scales.
Implications for Satellite and Free-Space Links
Beyond data centers, photonic lanterns have attracted attention for laser communications between satellites and ground stations. MIT Lincoln Laboratory has highlighted the technology’s ability to map few-mode fiber light to many single-mode outputs, a configuration that mitigates the pointing errors and mechanical vibrations inherent in space-based optical terminals. When a satellite jitters, the beam wanders across the receiving aperture, exciting different fiber modes unpredictably. A photonic lantern at the receiver can capture that wandering light and sort it into stable channels for processing.
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*This article was researched with the help of AI, with human editors creating the final content.
