201_Lombard_present
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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 THALES Research & Technology - Institut d'Optique ELSA AMPLI A FIBRE Pourquoi une fibre pour les lasers de puissance? Bon rendement Optique-Optique (bon recouvrement pompe et signal) Très hautes puissances accessibles (dans les fibres à grand cœur) Technologie performante: double cœur dopage Cœur pompe non dopé Yb disponibilité des diodes de pompe haute puissance Laser à fibre Signal Pompe Fibre MOPA 2 Cœur signal dopé THALES Research & Technology - Institut d'Optique ELSA Pompe Fibre 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 Pas de problème thermique (ils sont répartis sur la longueur) Puissance : Augmenter la taille du cœur! Fibres Multimodes: • Cœur 55µm / ON 0.2 (M²=10) Pump core Signal core 55µm 400µm Air-clad LMA (Tunnermann) Fibres Multicœurs, mise en phase spontanée 3 THALES Research & Technology - Institut d'Optique ELSA Multi-Fibres! 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 Fibres LMA (Large Mode Area) quasi monomodes: • Cœur 20µm / ON 0.06 • Cœur 30µm / ON 0.06 Multimode Fiber Amplifier Fiber characteristics: Input Signal Core Diameter 55 µm, NA 0.19 Doping 6500 ppm (mol) Yb2O3 Output Pump Core Pump : 60W @ 940 nm Signal : 0.5W @ 1064 nm Diameter 340x400 µm, NA 0.39 D-shape for pumping efficiency Amplified Signal : ~ 18 W, highly MultiMode (M² ~ 10) Pump core Signal core 55µm 400µm 4 THALES Research & Technology - Institut d'Optique ELSA Oscillator Pump MMFA MM 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 Amplifier characteristics: Recovering Beam Quality How to recover the beam quality of a Multimode Fiber Amplifier ? 2 approaches : SM Oscillator MM MMFA Pump Phase Conjugation SM MM Oscillator SM Pump 5 THALES Research & Technology - Institut d'Optique ELSA MMFA SM 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 Beam Cleanup How to recover Beam Quality ? Rh:BaTiO3 Photorefractive R crystal SingleMode Oscillator S Pump MMFA MultiMode Ampl. R SingleMode • R and S interfere in the crystal and write a /2-shifted volume hologram. • S energy (not its phase) is transferred to R 6 THALES Research & Technology - Institut d'Optique ELSA 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 1. Beam cleanup (two wave mixing in a photorefractive crystal) Phororefractive Beam Cleanup Reference PR crystal Aberrated signal 2 Amplified clean beam • Coupled wave equations : dI1 I1 I 2 G a I1 dz I1 I 2 1 (d ) 1 (0) I 2 (d ) dI 2 I1 I 2 G a I2 dz I1 I 2 2 (d ) 2 (0) I1 I 2 exp[(G a )d ] I1 I 2 exp(Gd ) • Rh:BaTiO3 : l = 1.06 µm, large G > 20 cm-1, low absorption a = 0.1 cm-1 7 THALES Research & Technology - Institut d'Optique ELSA 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 •2WM: Rh:BaTiO3 crystal Rh:BaTiO3 : an infrared sensitive (1.06 µm) photorefractive crystal cut at 45° from the crystal c-axis (to access large photorefractive gains) “roof shape” design to prevent any parasitic oscillation Rh:BaTiO3 gain versus Signal / Reference power ratio 104 1000 100 10 1 0.1 1 10 100 1000 Signal / Reference power ratio Maximum gain : 2000 (= exp[(G a)L]) Photorefractive gain : 24.6 cm-1 (= G) absorption : 0.1 cm-1 (= a) 8 THALES Research & Technology - Institut d'Optique ELSA 104 105 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 12.2 x 9.5 x 3.1 mm (W x H x D) Gain (2WM) Experimental Setup 1 Camera Phase stabilization l/2 Rh:BaTiO3 R Signal beam S Laser diode @ 920 nm Output 50 Residual pump FEEDBACK ON 40 Vertical polarization phase (rad) MMFA Yb-doped 0.6 m 30 20 10 Measured dephasing between R and S 0 -10 0 20 40 60 80 time (s) 100 120 140 160 140 160 power (Ar. Un.) 2 1.5 FEEDBACK ON 1 Output Power 0.5 0 9 THALES Research & Technology - Institut d'Optique ELSA 0 20 40 60 80 time (s) 100 120 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 Nd:YAG laser @ 1064 nm PZT Reference beam Self referencing Two Wave Mixing Setup Self referencing Two Wave Mixing Polarization recycling Unpolarized beam Polarization recycling: Insensitive to MM Fiber Amplifier depolarization Horizontal polarization Building Reference beam (Dot mirror + Spatial filter) Nd:YAG laser @ 1064 nm SF PBS Dot Mirror Laser diode @ 940 nm MMFA Yb-doped 4m 10 THALES Research & Technology - Institut d'Optique ELSA MM l/2 MM SM Rh:BaTiO3 R S Output 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 Vertical polarization Building Reference beam: Dot mirror and spatial filter Building Reference beam (Dot mirror + Spatial filter) To spatial filter to make it SM SM Reference (almost SM) DM MM MM Signal Aberrated (MM) 11 THALES Research & Technology - Institut d'Optique ELSA 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 SF Experimental results : Power Output Power vs time 10 S// S 8 S+ S// Rise time : 2-3s 6 4 2 0 0 50 100 150 200 250 300 350 400 450 500 Time (s) R = 110 mW (SM) 2.7 W • Crystal efficiency = 78% • Total Conversion efficiency = 63% S = 8.3 W S// = 6.6 W (Total 15W) 12 (SM) Ampl. R = 11.6 W THALES Research & Technology - Institut d'Optique ELSA 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 Output power (W) 12 Experimental results : Beam Quality M² = 1.0 Linearly polarized 1 0.8 0.6 0.4 0.2 Signals S and S// M² = 7.4 Depolarized 0 20 40 60 80 100 axial position (mm) 120 Amplified Reference M² = 1.2 Linearly Polarized 13 THALES Research & Technology - Institut d'Optique ELSA 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 Reference beam size (mm) 1.2 Power handling capability of Rh:BaTiO3 Depoling effect appears after several 100 hours of use. It reduces the conversion efficiency. The effect is temporary suppressed by illumination for several hours with 200mW, 532nm laser High power handling 14 Low-absorption crystals: photorefractive crystals with low absorption are more indicated. Co:BaTiO3 crystal is promising. Large aperture crystals THALES Research & Technology - Institut d'Optique ELSA 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 Rh:BaTiO3 Crystal depoling CONCLUSION Un oscillateur monomode est amplifié dans une fibre multimode. La qualité de faisceau est ramenée à la limite de diffraction par un Convertisseur Spatial de faisceau photorefractif entrée: faisceau dépolarisé multimode cohérent sortie: faisceau monomode linéairement polarisé 15 THALES Research & Technology - Institut d'Optique ELSA 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 • Presentation d’un nouveau concept et validation experimentale à 15W : Recovering Beam Quality How to recover the beam quality of a Multimode Fiber Amplifier ? 2 approaches : SM Oscillator MM MMFA Pump Phase Conjugation SM MM Oscillator SM Pump 16 THALES Research & Technology - Institut d'Optique ELSA MMFA SM 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 Beam Cleanup How to recover Beam Quality ? 2. Conjugaison de phase Miroir à conjugaison de phase SM Oscillator SM Pump MMFA Miroir conventionnel 17 THALES Research & Technology - Institut d'Optique ELSA Miroir à conjugaison de phase 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 MM Manip actuelle Conjugaison de phase par effet Brillouin SM MM SM Pump fibre multimode dopée 3m Fibre multimode non dopée 1km Miroir à conjugaison de phase par effet Brillouin 18 THALES Research & Technology - Institut d'Optique ELSA 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 Oscillator Effet Brillouin dans une fibre monomode Onde Stokes (réfléchie sur le réseau) Onde pompe Photon bruit Onde acoustique (réseau de Bragg) fibre monomode 13.6 km Puissance reflechie (ua) et Reflectivité du MCP fibre 13.6km, 8µm [email protected]µm 19 1 0.8 reflectivité 0.6 Puissance reflechie 0.4 0.2 0 Diffusion Brillouin Stimulée seuil 0 0.02 0.04 0.06 puissance en entrée (W) 0.08 0.1 THALES Research & Technology - Institut d'Optique ELSA (Stimulated Brillouin Scattering, SBS) 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 Diode laser monofréquence SBS comme Miroir à conjugaison de phase Milieux non guidants Onde Stokes Onde acoustique Bruit Onde pompe 20 THALES Research & Technology - Institut d'Optique ELSA « cellule SBS » (CS2) 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 Nécessite des kW crête! SBS comme Miroir à conjugaison de phase Onde pompe Onde acoustique Bruit ! « cellule SBS» (CS 2) Onde incidente Onde conjuguée en phase Mais sort conjugué en phase! 21 THALES Research & Technology - Institut d'Optique ELSA Démarre sur du bruit… 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 Onde Stokes SBS comme Miroir à conjugaison de phase Cellule Brillouin Champ de bruit Gain local Stokes Puissances globales Pompe, Stokes Gain global Stokes Speckle Stokes superposé au Speckle Pompe Speckle Stokes aléatoire Non CP CP gPp C=1 non conjugué en phase 22 Pour une aberration gausienne, l’intensité du Speckle volumique s’écrit e surf L THALES Research & Technology - Institut d'Optique ELSA 2 e gPp surf C=2; doublement du gain L conjugué en phase 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 Speckle volumique « modes » de la fibre n2 n1 mode 2 (LP 03) mode 1 (LP 02) mode 0 (LP 01) Fibre Multimode Longueur 1km Cœur à saut d’indice Diamètre 50µm, ON 0.22 23 THALES Research & Technology - Institut d'Optique ELSA 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 SBS dans une fibre multimode! Schéma idéal « cellule SBS» (CS2) SM kW crête! MM Oscillator SM Pump fibre multimode dopée 3m Fibre multimode non dopée 1km Miroir à conjugaison de phase par effet Brillouin 24 THALES Research & Technology - Institut d'Optique ELSA 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 Conjugaison de phase par effet Brillouin Phase conjugation by SBS : preliminary experiment (polarized) Laser (depolarized) (polarized) Multimode fiber 0.46 m Brillouin Brillouin Stokes Signal power 0.4 With a spherical mirror M²=3.6 Reflected Energy (mJ) 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 Input Energy (m J) 25 THALES Research & Technology - Institut d'Optique ELSA With a phase-conjugating mirror (0.46m fiber) M²=1.1 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 pulsed laser 20ns, 50Hz, single-frequency multimode fiber 0.07 m Simulation dans une fibre multimode à Saut d’indice Pompe Fibre multimode SI long. 0.5 m, diamètre 14µm, ON 0.22 Stokes Fidélité de la CP 90%. 0.2m 0.5m 1mm Pompe (entrée) Stokes (retour) 26 THALES Research & Technology - Institut d'Optique ELSA 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 entrée Pour une fibre un peu plus longue… Pompe Stokes Fibre multimode SI long. 2 m, diamètre 14µm, ON 0.22 Fidélité de la CP 20%. Pompe (entrée) 0.2m 0.5m 1m 1mm Stokes (retour) Aberrations chromatiques pour les fibres SI > qq. m Le conjugué en phase n’est plus favorisé. 27 THALES Research & Technology - Institut d'Optique ELSA 2m 5m 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 entrée CONCLUSION • Contrainte sur le milieu: •Suffisamment long pour qu’il y ait sélectivité (plusieurs grains de Speckle •Suffisamment court pour qu’il n’y ait pas aberration chromatique (grains de Speckle décalés) 28 THALES Research & Technology - Institut d'Optique ELSA 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 • Conjugaison de phase par diffusion brillouin stimulée: • Amplification exponentielle du bruit • Gain Double pour le conjugué en phase (<=> facteur ~104) CONCLUSION •Solutions •Utilisation d’une fibre à gradient d’indice, automatiquement corrigée des aberrations chromatiques •Utilisation du phénomène de « Beam Cleanup » sur grande longueur de fibre: un seul mode en retour, dépend du couplage. Pompe 29 THALES Research & Technology - Institut d'Optique ELSA Stokes 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 •Impulsionnel ou très fortes réflectivités pour réduit la longueur d’interaction
