Experimental Investigations on Passive Stabilization of Coherently Combined Multicore Fiber Systems

High power fiber lasers have become indispensable in industry and basic science due to their high efficiency, excellent beam quality, and compact design [1]. However, operating at high average powers and pulse energies introduces significant challenges, most notably thermal effects such as transverse mode instability (TMI) [2] and nonlinear phenomena [3], which degrade performance and limit a further power scaling. Coherent beam combining (CBC) offers a solution to these challenges by combining the outputs from multiple amplifier channels to form a single, high-quality beam [4]. Traditional CBC systems, however, rely on active phase control for all channels [5], leading to increased complexity and higher costs.