For a long time, interest in multimode (MM) optical fibers has remained limited, owing to the poor quality of laser beams emerging at their output. A typical indicator of beam quality is inversely proportional to the number of excited modes. However, recent intensive research of nonlinear propagation effects, involving high-power laser beams in MM graded-index (GRIN) fibers, has led to the discovery of previously unexpected phenomena, such as the Kerr-activated self-cleaning of a beam [1] . The manifestation of self-cleaning is that most of the beam energy flows into the fundamental mode of the fiber. This process is accompanied by a redistribution of energy towards higher-order modes [2] . Increasing the fundamental mode energy leads to improving the output beam quality. The standard method to determine the beam quality is to measure the M2-parameter (m-squared). This parameter measures the divergence of the beam with respect to the Gaussian beam. However, since self-cleaning involves a nonlinear redistribution of energy carried by a large number of fiber modes, this approach is not entirely correct, and a full mode decomposition (MD) of the output beam appears to be a much more informative method.

Mode dynamics during transition into Kerr self-cleaning regime for laser beams propagated in a multimode GRIN fiber / Gervaziev, Mikhail D.; Zhdanov, Innokentiy; Kharenko, Denis S.; Podivilov, Evgeniy V.; Babin, Sergey A.; Wabnitz, Stefan. - (2021), pp. 1-1. ((Intervento presentato al convegno 2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference tenutosi a Online only [10.1109/CLEO/Europe-EQEC52157.2021.9542580].

Mode dynamics during transition into Kerr self-cleaning regime for laser beams propagated in a multimode GRIN fiber

Wabnitz, Stefan
2021

Abstract

For a long time, interest in multimode (MM) optical fibers has remained limited, owing to the poor quality of laser beams emerging at their output. A typical indicator of beam quality is inversely proportional to the number of excited modes. However, recent intensive research of nonlinear propagation effects, involving high-power laser beams in MM graded-index (GRIN) fibers, has led to the discovery of previously unexpected phenomena, such as the Kerr-activated self-cleaning of a beam [1] . The manifestation of self-cleaning is that most of the beam energy flows into the fundamental mode of the fiber. This process is accompanied by a redistribution of energy towards higher-order modes [2] . Increasing the fundamental mode energy leads to improving the output beam quality. The standard method to determine the beam quality is to measure the M2-parameter (m-squared). This parameter measures the divergence of the beam with respect to the Gaussian beam. However, since self-cleaning involves a nonlinear redistribution of energy carried by a large number of fiber modes, this approach is not entirely correct, and a full mode decomposition (MD) of the output beam appears to be a much more informative method.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1579276
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