High-throughput polarization-independent spatial mode shaping with mode-selective photonic lanterns

Abstract: Coherent interference in multimode photonic systems offers a transformative approach for scalable, high-fidelity optical control, enabling precise beam shaping, efficient power delivery, and advanced signal processing through single-mode performance. Current techniques are often constrained to a single polarization state of light, system complexity, and the fabrication challenges associated with precise waveguide structures. Here, we present a high-efficiency coherent combination scheme employing a commercial mode-selective photonic lantern supporting three spatial channels, achieving Gaussian mode interference at multiple locations along the multimode core with up to 100% mode conversion efficiencies. By integrating a Faraday reflecting fibre component and piezo-phase shifters with the photonic lantern channels, we demonstrate stable and adaptive mode manipulation without the need for complex adaptive optics. These findings highlight the potential of photonic lanterns as robust platforms for controlled mode interference, paving the way for their deployment in next-generation optical communication, beam shaping, and beam-forming systems.