Pump-modulation-induced beam stabilization in high-power fiber laser systems above the mode instability threshold

A new way of stabilizing the output beam of a fiber laser system operating above the mode instability threshold is described and the first proof-of-principle experimental results are presented. This technique, which relies on a modulation of the pump power, works by washing the thermally-induced refractive index grating out, which weakens the coupling efficiency between transverse modes. One of the main advantages of this simple, yet powerful, approach is that it can be easily incorporated in already existing fiber laser systems since it does not require any additional optical elements. Using this beam stabilization strategy, a significant pointing stability and beam quality improvement has been demonstrated up to an average power of similar to 600W, which is a factor of 2 above the mode instability threshold. (C) 2018 Optical Society of America under the terms or the OSA Open Access Publishing Agreement