Design, Fabrication, and Free-Space Characterization of a Two-Photon-Polymerized Nano-printed Photonic Lantern
Photonic lanterns provide an interface between multimode optical fields and arrays of single-mode waveguides, making them promising components for modal filtering, wavefront sensing, and high-contrast astronomical instrumentation. We present the design, simulation, two-photon-polymerization fabrication, and free-space characterization of a compact photonic lantern optimized for operation at $ 1050~\mathrm{nm} $. The device was designed to transform a multimode input into five nominally single-mode output waveguides. Eigenmode-expansion simulations in Ansys Lumerical MODE were used to optimize the lantern geometry while minimizing insertion loss and output-channel power nonuniformity. The optimized structure was fabricated using a Nanoscribe Photonic Professional GT2 two-photon-polymerization system and developed as a standalone polymer-waveguide component. The fabricated lantern was characterized using a free-space optical setup consisting of a $ 635~\mathrm{nm} $ laser for preliminary characterization, collimation and focusing optics, and camera-based imaging of the transmitted fields. Measurements were used to assess optical throughput, output intensity distribution, and light-guiding performance. Differences between simulated and measured results may arise from the wavelength mismatch, fabrication tolerances, material and surface-scattering losses, alignment errors, and deviations from the idealized material and geometric parameters used in simulation. These results demonstrate a compact, additively manufactured photonic-lantern platform and establish a pathway toward free-space-coupled astrophotonic systems for future high-contrast exoplanet-imaging instrumentation.