20 February 2007 Numerical modeling of self-focusing beams in fiber amplifiers
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We have numerically investigated the behavior of the LP01 fundamental mode of a step-index, multimode (MM) fiber as the optical power approaches the self-focusing limit (Pcrit). The analysis includes the effects of optical gain and fiber bending and are thus applicable to coiled fiber amplifiers. We find that at powers below Pcrit, there exist stably propagating power-dependent modifications of the LP01 mode, in contrast to some previous solutions that exhibited large-amplitude oscillations in beam waist along the fiber. For the first time, to our knowledge, we show that in a MM fiber amplifier seeded with the low-power LP01 eigenmode, the transverse spatial profile will adiabatically evolve through power-dependent stationary solutions as the beam is amplified toward Pcrit. In addition, for a given value of the nonlinear index, Pcrit is found to be nearly the same in the bulk material and in a step-index fiber. These conclusions hold for both straight and bent fibers, although the quantitative details are somewhat different.
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Roger L. Farrow, Roger L. Farrow, G. Ronald Hadley, G. Ronald Hadley, Arlee V. Smith, Arlee V. Smith, Dahv A. V. Kliner, Dahv A. V. Kliner, } "Numerical modeling of self-focusing beams in fiber amplifiers", Proc. SPIE 6453, Fiber Lasers IV: Technology, Systems, and Applications, 645309 (20 February 2007); doi: 10.1117/12.701571; https://doi.org/10.1117/12.701571


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