Massive-scale spatial multiplexing of multimode VCSELs with a 3D-printed photonic lantern

Incoherent beam combining is a widely exploited approach in high-power laser systems due to its simplicity, stability and scalability, avoiding the need for frequency, phase and polarization locking. However, efficiently coupling light from large array sources, such as multi-mode vertical-cavity surface-emitting laser (VCSEL) arrays into a multimode fiber (MMF) of the same modal dimension for preserving brightness, remains challenging. This work introduces a novel solution for incoherent and efficient source collection: a 3D-printed micro-scale photonic lantern (PL) spatial multiplexer, designed to multiplex multiple multi-mode sources directly into MMFs supporting a matching number of aggregate modes. We present the design, fabrication, and characterization of three PL devices accepting 7, 19, and 37 multimode VCSELs having 6 spatial modes fabricated using nanoscale 3D printing directly on the laser chip output apertures. These PL devices enable direct transmission and coupling from VCSEL arrays to MMFs, achieving coupling efficiency as low as -0.6dB for the 19-MM PL and -0.8dB for the 37-MM PL when coupled to a step-index MMF with a 50 μm core diameter and NA = 0.22. Comprehensive experimental results demonstrate efficient power delivery, preserved brightness, and alignment-free integration, highlighting the potential of 3D-printed PL devices as compact and scalable solutions for high-power laser systems and other optical applications as communications.