Co-phase combining of laser array via silicon-based beam combiner

Phased fiber laser arrays provide an effective means to mitigate atmospheric turbulence and achieve high-quality beams, where efficient combiners play a crucial role in achieving phase coherence among sub-beams and generating high-power output beams. This paper focuses on investigation of a silicon-based beam combiner with 19 input channels, which employs a structure comprised of cascaded 2 × 1 multi-mode interference couplers and 2 × 1 Mach-Zehnder interferometers on a silicon chip. According to the thermo-optic effect of silicon material, the square of the control voltage is linearly related to the phase change. In response, the modified stochastic parallel gradient descent (SPGD) algorithm is proposed, and parameters are analyzed. Experimental results confirm that the silicon-based beam combiner with the modified SPGD algorithm can combine laser beams effectively. Under static conditions, after about 0.09 s of iteration, the output power of the silicon-based beam combiner reaches the average value detected by photodetector (PD), with a phase-locking accuracy of approximately λ /36. Under dynamic disturbance conditions, after about 0.3 s of iteration, the output power reaches the average value detected by PD, with a phase-locking accuracy of approximately λ /32.