Cascaded Internal Phase Control of All-Fiber Coherent Fiber Laser Array

Abstract

Fiber lasers have been widely used in medical care, industries, and scientific research in recent years. The coherent beam combining of fiber lasers with an internal phase control has drawn many interests at present, which is a promising method to achieve a large-scale optical phased array. In this article, we presented a cascaded internal phase control method to expand the internal all-fiber phased array. The method distributes the phase measurements to a series of internal Mach–Zender interferometers. Then, the phase of each loop is locked by the gradient descent algorithm. The electric control method to compensate π-ambiguity between channels is proposed. Finally, the phases of the three fiber beams are locked experimentally to verify the feasibility of the method, and the residue phase error is better than λ/22.