Coherent beam combining of high-order-mode fiber lasers with active phase control

摘要

Coherent beam combining of high-order-mode fiber lasers is an attractive choice for high-power lasers as high-order-mode fiber lasers have a higher power handling capability than fundamental mode lasers. As active phasing provides a robust way for in-phase mode coherent beam combining, coherent beam combining of high-order-mode fibers with active phase control is proposed and a proof-of-concept experiment is performed. In the experiment, LP 11 mode lasers are generated by off-center launching of single-mode fiber laser beams into few-mode fibers and active phasing is realized using a stochastic parallel gradient descent algorithm. The results show that the long-exposure fringe contrast is increased from zero to 40% when the system evolves from open-loop to closed-loop. A scalable architecture for coherent beam combining of high-order-mode amplifiers with active phase control in a master oscillator power amplifier configuration (MOPA) is also proposed.