Transcript
57-mJ multi-Hz multipass laser amplifier based on Yb:CaF2 Crystals Florence Friebel*1, Alain Pellegrina2, Dimitris N.Papadopoulos2, Patrice Camy3, Jean-Louis Doualan3, Richard Moncorge3, Patrick Georges1, Frédéric Druon1 1. Laboratoire Charles Fabry, Institut d'Optique (LCF), CNRS, Univ. Paris Sud, Palaiseau, France 2. Laboratoire d’Utilisation des Lasers Intenses (LULI), Ecole Polytechnique, Palaiseau, France 3. Centre de Recherche sur les Ions, les Matériaux et la Photonique(CIMAP), Caen, France
[email protected] JNCO – Cherbourg – June 11th 2013 http://www.lcf.institutoptique.fr/lcf-en
Outline
• Cilex-Apollon project • High-energy Yb:CaF2 multipass amplifiers • High energy multipass amplifier at 20 Hz • Thermal survey of crystals at 100Hz • Conclusion
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Apollon 10 PW laser
Front End OPCPA based 10fs,100mJ, >20Hz
Amplification Stages based on Ti:Sa 300 J @ 800 nm
Compressor 15 fs, 150 J @ 800 nm, 1pulse/mn
Pump Laser Nd:glass 0.8 KJ, 1pulse/mn LABORATOIRE CHARLES FABRY
JNCO 2013 – M12
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The Apollon front end source Signal source @ 800 nm Ti:Sapphire CPA 25 fs, 1.5 mJ
Nonlinear pulse compression/cleaning <10 fs, CR>1012
800 nm
OPCPA Multi-stages based on BBO crystals
Ti:Sapphire oscillator < 7 fs
1030 nm Diode pumped high energy amplifiers based on Ytterbium doped crystals J range@ 515 nm by SHG >20 Hz
< “10 fs” stretched to > 1 ns 100 mJ, >20 Hz
Pump source @ 515 nm JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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1030-nm CPA chain 1030 nm injection Ti:Sapphire oscillator
…to OPCPA signal @800nm
~4 pJ@1030nm YDFA
Yb:KYW regen. 2mJ
BS
Yb:YAG regen (M.B.I.) >200 mJ 100Hz
Compr. ~16 ps
Picosecond Stage
Stretcher, 0.5ns/nm
ps-OPCPA SHG ~60%
Nanosecond Stage MP1
MP2
MP3
CaF2
Yb:CaF2
Yb:CaF2
>20 mJ, >20 Hz
~200 mJ, >20 Hz
JNCO 2013 – M12
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SHG >50%
>80 mJ, ~12 ps 100 Hz @515 nm
ns-OPCPA J,~1.5 ns >20 Hz @515 nm
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Material for high-energy amplifiers
• New revival of an old Crystal
Yb:CaF2 • Large Bandwidth (<100fs) • Good thermal conductivity(~YAG) • Long fluorescence lifetime (2.4 ms) − −
Low Emission cross section Low gain
W. Humphreys, Astrophysical Journal, 266 (1904) A. Lucca, et al. Opt. Lett. 1879 (2004) A. Lucca, et al. Opt. Lett. 2767 (2004) M. Siebold, et al. Opt. Lett., 2770 (2008). F. Friebel, et al. Opt. Lett.,1474–1476 (2009) F. Druon, et al. IEEE Photonics Journal Vol. 3, 2, 268 (2011) F. Druon, et al. Opt. Material Exp. 1, 489 (2011) JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Outline
• Cilex-Apollon project • High-energy Yb:CaF2 multipass amplifiers • High energy multipass amplifier at 20 Hz • Thermal survey of crystals at 100Hz • Conclusion
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Experimental setup 115cm
30cm
ROC: 2m
980nm, 400W, 20 Hz, 2,25 ms, 1.8 J, 36 W
1:3.75
Yb:CaF2 2mm,2,2%
Npass = 8
S-pulse Yb:KYW regenerative amp. 1kHz, 2mJ, 3-5nm,1030nm
λ/2 Output Reinjection
…~pJ @1030nm from the Ti:Sapphire oscillator
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Experimental setup 115cm
30cm
ROC: 2m
980nm, 400W, 20 Hz, 2,25 ms, 1.8 J, 36 W
JNCO 2013 – M12
Yb:CaF2 2mm,2,2%
Npasses =8
Output 53mJ,100Hz λ/2 3.1nm, 1030nm Reinjection
x2
1:3.75
Total Npasses = 16 http://www.lcf.institutoptique.fr/lcf-en
S-pulse Yb:KYW regenerative amp. 1kHz, 2mJ, 3-5nm,1030nm …~pJ @1030nm from the Ti:Sapphire oscillator 9
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Outline
• Cilex-Apollon project • High-energy Yb:CaF2 multipass amplifiers • High energy multipass amplifier at 20 Hz • Thermal survey of crystals at 100Hz • Conclusion
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Simulation-Expected output Stored energy & extraction efficiency estimation Population inversion level in the CaF2 Crystal
980nm, 400W, 20 Hz, 2,25 ms, 1.8 J, 36 W
E out (J)
E stored (J)
Operating point
Number of passes
• Stored energy estimation: Esto~150mJ (Ep~1.2J, Δtpump~ 2,25 ms) • With: Np.max = 15 Eout,theory > 60 mJ JNCO 2013 – M12
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Results EFirst pass / mJ Eout / mJ
Eout / mJ
57,4 mJ
Einjection / mJ
• Eout~57,4 mJ @ 20 Hz , Np~15, Einput ~1,1mJ Gain is 32 JNCO 2013 – M12
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Beam Quality Output
Excellent beam quality M2 ~ 1.1
•30 min running @ 50 mJ
•The pointing stability<20μrad
JNCO 2013 – M12
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Temperature Profile 30 28 26 24 22 20 18 16 14
Trace 1) Trace 2) Trace 3)
heat
HR – coating
Heat spreader
AR-coating
Temperature / Cº
Active mirror
Temperature / Cº
Local surface temperature profile at maximum pumping Image By Thermal Camera (7.5 – 13 µm) Surface of CaF2-Crystal in Mount (right)
(Below) Heat conduction on the crystal for pumping from 0 - 400 W in three steps • max. surface temperature 28 ºC (max. increase of +15 ºC)
30 28 26 24 22 20 18 16 14
1) 28 ºC
1) 28 ºC
2) 23 ºC
2) 23 ºC
Good thermal management Low heating 3) 15 ºC 0
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6 Time/ min
JNCO 2013 – M12
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3) 15 ºC 8
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Spectrum
•∆λ=3.1 nm, FTL~600 fs (∆t~1.5 ns) / Injection spectrum limited JNCO 2013 – M12
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Outline
• Cilex-Apollon project • High-energy Yb:CaF2 multipass amplifiers • High energy multipass amplifier at 20 Hz • Thermal survey of crystals at 100Hz • Conclusion
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Thermal Profile
Trace across diameter of crystal including the central heating part
Temperature / Cº
30 28 26 24 22 20 18 16 14
Temperature / Cº
Local surface temperature profile at maximum pumping Image By Thermal Camera (7.5 – 13 µm) Surface of CaF2-Crystal in Mount (right)
(Below) Heat conduction on the crystal for pumping at 400 W • max. surface temperature 28 ºC (max. increase of +15 ºC)
30 25 20 18 16 14
Cooling very efficient Using the active mirror configuration - from the backside JNCO 2013 – M12
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Thermal lens measurement
Dioptric Power [ m-1]
Thermal lens dependency on pump power
Thermal lens 100 Hz
Incident pump power [W]
The thermal lens is POSITIVE JNCO 2013 – M12
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Thermal lens: Positive ? BUT Our hypothesis
Crystal in active mirror configuration
« Bilame » effect
AR-coating (thin= softer)
HR – coating (thick= harder)
Yb:CaF2
heat
Add an asymetric mechanical distortions Even with thermooptic coefficient
cCaF2 < 0
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Thermal lens: Dynamics
Pump [a.u]
Dioptric power variation [%]
Measurement of the instantaneous thermal lens
Time / ms Thermal lens Theoretical current JNCO 2013 – M12
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Fluorescence Pump 2020
Thermal lens: Dynamics
Pump [a.u]
Temporal delay between thermal lens and heat load
The thermal load follows the fluo and not the pump ! JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Thermal lens: Dynamics Temporal delay between thermal lens and heat load View from the energetic scheme We have to wait for the fluorescence before the heating
Fluo Pump
Quasi exclusive heat source Non-radiative deexcitation = HEAT JNCO 2013 – M12
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Outline
• Cilex-Apollon project • High-energy Yb:CaF2 multipass amplifiers • High energy multipass amplifier at 20 Hz • Thermal survey of crystals at 100Hz • Conclusion
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Conclusion • High energy multipass amplifier Eout = 57 mJ • Repetition Rate 20 Hz • Excellent beam quality M2 ~ 1.1, with 16 Passes • The crystals handle 100 Hz heat load • Positive thermal lens : active mirror≠brewster crystal • Thermal lens dynamic linked to fluorescence shape Current stability issues: management of the fluorescence irradiation that could heat the closest mounts to the crystal => air turbulences. JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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Merci pour votre attention
JNCO 2013 – M12
http://www.lcf.institutoptique.fr/lcf-en
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