MPLC-based incoherent combining of fibered QCLs for advanced infrared countermeasures

Authors: Louis Andréoli, Lucie Guestin, David Kerloch, Pierre Vernaz-Gris, Gauthier Trunet, Quentin Barbedienne, Guillaume Labroille, Pu Jian

Cailabs, Rennes – FRANCE

Abstract

The delivery of high-power mid-infrared laser light through fiber optics is essential for advanced aircraft defense systems such as Directional Infrared Countermeasures (DIRCM). Quantum Cascade Lasers (QCLs) emitting at 4-5 µm are a preferred solution but suffer from output power limitations. We present a novel, compact approach for scaling output by multiplexing eight independents fibered QCLs using Multi-Plane Light Conversion (MPLC) technology. Custom phase-shaping elements are used to match the laser emission to the modal profile of indium fluoride fibers, enabling efficient fiber coupling and system miniaturization. Experimental data demonstrate the achieved injection rates, the combined system power, overall combination efficiency, and output beam quality (M²), underlining the method’s suitability for portable DIRCM platforms.