Researchers have developed a microscopic 3D-printed optical device that can efficiently combine light from dozens of small semiconductor lasers into a single multimode optical fiber with very low loss. The team demonstrated photonic lanterns that multiplex 7, 19, and 37 multimode VCSEL lasers directly into a fiber while preserving brightness and easing alignment constraints. By enabling scalable incoherent beam combining of many multimode lasers, the technology could simplify and improve high-power laser systems, optical communications, and other photonic applications where efficiently delivering large optical power through fibers is critical.

A new study published in Nature Communications by Ph.D. student Yoav Dana, under the guidance of Professor Dan M. Marom and his team at the Institute of Applied Physics at the Hebrew University of Jerusalem, Israel, demonstrate a significant breakthrough in system scale and miniaturization for an optical beam combining apparatus, as those required in high-power laser systems.

The research, conducted in collaboration with Civan Lasers and funded by Israel Innovation Authority, introduces a novel 3D-printed microscale Photonic Lantern (PL) designed for the efficient incoherent combining of multimode sources. This innovation addresses the long-standing challenge of coupling light from large Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays, each of said VCSEL sources being multimoded, into multimode fibers (MMFs) while preserving the brightness and modal capacity of the system.
Key Advancements:

• Realization of the first Multimode Photonic Lantern (MM PL): While traditional photonic lanterns interface between multiple single-mode (SM) inputs and a single multimode waveguide, this research successfully realizes a novel "N-MM PL" architecture that supports many multimode VCSEL sources multiplexed into a single high mode count waveguide.
• Massive Scalability: The team successfully demonstrated PLs capable of multiplexing 7, 19, and even 37 VCSEL sources with each lasing across six-spatial modes into a single multimode optical fiber, supporting a total of up to 222 spatial modes.
• High Efficiency at diminutive size: The devices achieved low coupling losses into standard 50 μm multimode fiber, as low as -0.6 dB for 19-input PLs and -0.8 dB for 37-input PLs, with the entire PL requiring less than ½ mm in length, which is many orders of magnitude smaller than competing optical multiplexing system
• Preserved Brightness: Unlike traditional relay lens systems that often diminish beam quality, this "N-MM PL" architecture matches modal capacity to preserve brightness, a critical factor for high-performance optical systems.

Technical Breakthrough:
Traditionally, Photonic Lanterns were designed for single-mode inputs, making them incompatible with the multimode outputs of high-power VCSEL arrays. The Hebrew University team overcame this by designing an adiabatic transition that converts multiple few-mode sources into a single multimode fiber with matched degrees of freedom. Despite their massive-scale capability, these devices remain incredibly compact with the 37-input PL measuring only 470 μm in length.