201_Lombard_present

THALES Research & Technology - Institut d'Optique ELSA
Remise en forme de faisceau
après un amplificateur à fibre multimode
L. Lombard, A. Brignon, J.P. Huignard, E. Lallier
TRT (Thales Research and Technology)
G. Lucas-Leclin, P. Georges, G. Pauliat, G. Roosen
Laboratoire Charles Fabry de l’Institut d’Optique

This document and any data included are the property of THALES. They cannot be reproduced, disclosed or used without THALES' prior written approval. ©THALES 2003. Template trtco V 6.0.0
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AMPLI A FIBRE
Pompe
Signal
Fibre
Pourquoi une fibre pour les lasers de
puissance?
Bon rendement Optique-Optique (bon recouvrement pompe et signal)
Pas de problème thermique (ils sont répartis sur la longueur)
Très hautes puissances accessibles (dans les fibres à grand cœur)
Technologie performante:
double cœur
dopage Yb
disponibilité des diodes de pompe haute puissance
MOPA Pompe Fibre
Laser à fibre
Cœur signal dopé
Cœur pompe non dopé

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Puissance : Augmenter la taille du cœur!
Fibres LMA (Large Mode Area) quasi
monomodes:
•Cœur 20µm / ON 0.06
•Cœur 30µm / ON 0.06
Air-clad LMA (Tunnermann)
400µm
55µm
Signal core
Pump core
Fibres Multimodes:
•Cœur 55µm / ON 0.2 (M²=10)
Fibres Multicœurs, mise en phase
spontanée
Multi-Fibres!

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Multimode Fiber Amplifier
Amplifier characteristics:
Input
Pump : 60W @ 940 nm
Signal : 0.5W @ 1064 nm
Output
Amplified Signal : ~ 18 W, highly
MultiMode (M² ~ 10)
400µm
55µm
Signal core
Pump core
Pump
Oscillator
MMFA MM
Fiber characteristics:
Signal Core
Diameter 55 µm, NA 0.19
Doping 6500 ppm (mol) Yb2O3
Pump Core
Diameter 340x400 µm, NA 0.39
D-shape for pumping efficiency

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Recovering Beam Quality
How to recover the beam quality of a Multimode Fiber Amplifier ?
2 approaches :
Pump
Oscillator
MMFA SM
SM
MM
MMFA
Pump
Oscillator
MM
SM
SM
Beam Cleanup
Phase Conjugation