3D Printed mode-selective micro-scale photonic lantern spatial (de)multiplexer

We present the design, fabrication, and characterization of a mode selective Photonic Lantern (PL) supporting three modes, measuring only 300𝜇𝑚 in length, for converting between three single-mode input sources and a single three-mode optical fiber. The PL is fabricated directly on a multi-core fiber serving as a source) using a commercial two-photon polymerization-based 3D printer. Despite the diminutive size and high index contrast of the polymer core/air cladding waveguides, we observed low insertion loss (less than -1.7 dB), low polarization dependent loss (less than -0.25 dB), mode dependent loss of −1.7𝑑𝐵, low wavelength dependence, and mode group cross-talk of less than −16𝑑𝐵. We demonstrate mode-group multiplexed transmission using our mode-selective multiplexer/demultiplexer pair and a short three-mode fiber link in an intensity modulation/direct detection (IM/DD) experiment, recovering two 12.5𝐺𝑏/𝑠 signals without MIMO processing.