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Asymmetric taper scrambler for improved pump homogeneity and absorption in side-pumped double-clad fibre lasers
A multimode optical fiber scrambler (MOFS) based on an asymmetric taper is demonstrated. The MOFS contains an adiabatic down-taper transition and an abrupt up-taper transition made into a double cladding fiber. This device improves the pump power absorption by two principal effects which adapt the s...
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Published in: | Laser physics letters 2019-08, Vol.16 (8), p.85105 |
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Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | A multimode optical fiber scrambler (MOFS) based on an asymmetric taper is demonstrated. The MOFS contains an adiabatic down-taper transition and an abrupt up-taper transition made into a double cladding fiber. This device improves the pump power absorption by two principal effects which adapt the side-coupled cladding light. The first one is to homogenize the ring-shaped light distribution from a side pump combiner before being launched into an active double-clad fiber. Secondly, provided the conservation of etendue, the low NA of that multimode beam is transformed during its propagation through the longer taper transition of the MOFS device. Then, a net NA increment occurs, so that it fills the full input NA of this fiber at the taper waist. The up-taper transition is non-adiabatic for the multimode beam so that it exits from the taper with the transformed NA. The MOFS was inserted into a >200 W fiber laser cavity and significantly improved the effective pump absorption from 0.6 dB m−1 to 1.8 dB m−1. |
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ISSN: | 1612-2011 1612-202X |
DOI: | 10.1088/1612-202X/ab2805 |