The modal instability (MI) threshold is estimated for four rod fiber designs by combining a semi-analytic model with the finite element method. The thermal load due to the quantum defect is calculated and used to numerically determine the mode distributions on which the expression for the onset of MIs is highly dependent. The relative intensity noise of the seed laser in an amplifier setup is used to seed the mode coupling between the fundamental and higher order mode, and lead to MI threshold values of 174 W – 348 W of extracted output power for the four rod fibers having core diameters in the range 53 μm – 95 μm.
Proceedings of Spie, the International Society for Optical Engineering, 2013, Vol 8601
Fiber amplifiers; Modal instability; Microstructured fibers; High power amplifiers; Thermal effects
Main Research Area:
SPIE Photonics West : Fiber Lasers X: Technology, Systems, and Applications, 2013