Numerical simulation of coherent beam combining of large-array fiber lasers via Zernike’s phase-contrast

One of the development trends in coherent beam combining (CBC) of fiber lasers is towards larger array numbers. Effective phase control represents a critical element in CBC of a large-scale fiber laser array. Herein, a novel phase-locking scheme for the CBC system based on Zernike’s phase-contrast (ZPC) method is proposed. A spatial filtering structure is employed, comprising a Zernike phase mask functioning as a phase filter in the spectrum plane and a photodetector array corresponding to individual beams positioned on the image plane. The phase difference between the beams can be identified by measuring the intensity distribution on the image plane. Numerical simulations of the control algorithm validate the efficacy of this technique across laser arrays ranging from 7 to 331 channels. The findings indicate that the convergence steps are all within a range of 20. Further analysis reveals that the proposed method is robust against power inconsistencies, power fluctuations, and the misalignment of the phase mask. The proposed algorithm’s parallel processing and rapid convergence capabilities result in a reduction in the demand for the response frequency of the phase modulators while maintaining high control bandwidth. The ZPC technique could provide valuable insights into the design of the CBC system with large-array fiber lasers.