Investigation of the influence of optical nonlinearity on combining efficiency in ultrashort pulsed fiber laser coherent combining system

In this paper, the influence of optical nonlinearity on combining efficiency in ultrashort pulsed fiber laser coherent combining system is investigated theoretically and experimentally. In the theoretical work, a new theoretical algorithm for the coherent combining efficiency, which can be used to quantify the spectral coherence decay induced by optical nonlineary imbalance between the sub-beams, is presented. The spectral information of the sub-beam is obtained by numerically solving the nonlinear Schrödinger equation (NLSE) in this algorithm to ensure an accurate prediction. In the experimental work, the coherent combining of two all-fiber picosecond lasers is achieved, and the influence of imbalanced optical nonlinearity on the combining efficiency is studied, which agrees with the theoretical prediction. This paper reveals the physical mechanism for the influence of optical nonlinearity on the combining efficiency, which is valuable for the coherent combining of ultrashort pulsed fiber laser beams.