Array size scalability of passively coherently phased fiber laser arrays.

We explore, by means of experiments and simulation, the power combining efficiency and power fluctuation of coherently phased 2, 4, 6, 8, 10, 12, 14, 16-channel fiber-laser arrays using fused 50:50 single-mode couplers. The measured evolution of power combining efficiency with array size agrees with simulations based on a new propagation model. For our particular system the power fluctuations due to small wavelength-scale length variations are seen to scale with array size as N(3). Beat spectra support the notion that a lack of coherently-combined supermodes in arrays of increasing size leads to a decrease in combined-power efficiency.