Research on phase-detecting method for coherent combining beams in fiber laser array

Abstract

A novel method for phase-detecting of each individual beam in coherent beam combining system of fiber laser array based on the property of time-shift of fast Fourier transform is reported. It takes advantage of the relative movement of fringe-pattern to detect the phase shift between each individual beam and reference beam. No frequency shift component for reference beam is required in the system. At the same time, the acquisition fringe-pattern is firstly tailored to a few multiple of fringes in order to reduce the phase-detecting error caused by energy leakage during the course of fast Fourier transform. This technique can greatly reduce the effect of energy leakage and thus improve the phase-detecting precision. Basic principle of the new phase-detecting method is described in detail, and numerical results show that the phase-detecting error is less than 1/1000 wavelength by utilizing our method.

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