We report the production of stable, coherent, and same-phase states in arrays of fiber lasers. Provided that proper interactions between the lasers are present, arrays will spontaneously self-organize into stable coherent same-phase states. There is no need for active control. Power scaling, power spectra, spatial interference fringes, and temporal data all support this conclusion.

We experimentally demonstrate 50 W of spontaneously phase-locked two-laser array in an all-fiber and all-passive configuration using large-mode-area (LMA) polarization-maintaining fiber laser cavities and an LMA fiber coupler. We show that both laser cavity length difference and fiber nonlinearity play an important role in achieving efficient and stable coherent beam combining. In addition, we compare the difference in coherent combining efficiency by using fibers with different mode-field diameters and discuss the underlying phase-locking mechanism and its power scalability.

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Self-organized coherence between fiber lasers has been reported both via all-fiber 2x2 directional coupler trees and in spatially multi-core fibers. We have taken this a major step forward, coupling together a number of independent fiber lasers to obtain a spatially and spectrally coherent far field, with no active length, polarization, or amplitude control. The near field output comes from a spatial array rather than from a single fiber, making this approach scalable to extremely high power.