Intense lasers: high peak power Part 2: Propagation Bruno Le Garrec - - PowerPoint PPT Presentation

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Intense lasers: high peak power Part 2: Propagation Bruno Le Garrec Directeur des Technologies Lasers du LULI LULI/Ecole Polytechnique, route de Saclay 91128 Palaiseau cedex, France bruno.le-garrec@polytechnique.edu 31/08/2016 Bruno Le

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Intense lasers: high peak power Part 2: Propagation

Bruno Le Garrec

Directeur des Technologies Lasers du LULI LULI/Ecole Polytechnique, route de Saclay 91128 Palaiseau cedex, France bruno.le-garrec@polytechnique.edu 31/08/2016

LPA school Capri 2017

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CNE400 : half kilojoule laser Continuum - National Energetics

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CNE400: 1.5 m x 6 m

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CNE400

CNE400 is delivering 200 J @ 527 nm @ 1 shot/mn rep-rate (and 300J IR)

  • Beam diameter 60 mm, low divergence

(< 0,2 mrad) and poyntingstability =22 microrads RMS)

  • Pulse shaping capability: 40 ns
  • Phase modulation for smoothing

purpose (« SSD »)

  • Deformable mirror
  • T. Ditmire et al (2014), CLEO 2014, Technologies for high

intensity (STU3F), doi:10.1364/CLEO_SI.2014.STu3F.1

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Next step: L4 for ELI-Beamlines

Front-end ps OPCPA + Pulse cleaner Stretcher ns OPCPA 2 Power Amplifiers 1.7 kJ To compressor

  • 2 main amps : 1 multipass 180 mm + 1 booster 300 mm
  • Mixed silicate and phosphate laser glasses
  • Expected up to 2 kJ stretched – 1.5 kJ compressed to 150 fs
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Multiple pass amplifier with adaptive optic

  • It can be shown that this configuration is the best one for

correcting the wave front

  • Both NIF and LMJ prototype (LIL facility) have achieved more than

85% THG efficiency

  • Both NIF and LMJ prototype (LIL facility) can fire every 2 hours

(amplifier slabs are not cooled)

  • LLE (OMEGA EP) while using this type of amplifier with water

cooled lamps (but still un-cooled slabs) can fire every hour.

Deformable Mirror Disks amplifier Lens Pinhole 1st & 3rd pass 2nd & 4th pass

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Wavefront Correction

  • Wavefront distortions are coming from:

– Dynamic aberrations from thermal effects in the amplifiers – Static aberrations from optical components

  • Deformable mirror & spatial filtering

FST M2 MdT2 Mi3 Mi2 L1 L2 L3 LdT Li Mi1 Mi4 Mi5 MdT1

AMPLIFIER 9 LASER GLASS SLABS AMPLIFIER 9 LASER GLASS SLABS

COMPUTER

MDA MT1 L4

toward3 w section WAVEFRONT SENSOR

DFM

FST M2 MdT2 Mi3 Mi2 L1 L2 L3 LdT Li Mi1 Mi4 Mi5 MdT1

AMPLIFIER 9 LASER GLASS SLABS AMPLIFIER 9 LASER GLASS SLABS

COMPUTER

MDA MT1 L4

toward3 w section WAVEFRONT SENSOR

FST M2 MdT2 Mi3 Mi2 L1 L2 L3 LdT Li Mi1 Mi4 Mi5 MdT1

AMPLI 9 LASER GLASS SLABS AMPLIFIER 9 LASER GLASS SLABS

COMPUTER

MDA MT1 L4

toward3 w section WAVEFRONT SENSOR

DFM

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Wavefront correction loop

Wavefront correction sofware

Section Transport Section Conversion en fréquence et Focalisation

Reference Source at FST4 Deformable Mirror

Open or close Loop 30-mn Stability

Wavefront sensor

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Wavefront Correction

FST1 = AbINJ FST2 = AbINJ + 2 AbAMPLI FST3 = AbINJ + 2 AbAMPLI + 2 AbDT FST4 = AbINJ + 4 AbAMPLI + 2 AbDT When applying the correction - ( AbINJ + 4 AbAMPLI + 2 AbDT)/2 to the deformable mirror, one gets: FST1 = AbINJ FST2 = ½ AbINJ – AbDT FST3 = ½ AbINJ + AbDT FST4 = 0.

Δϕ = 53,9 rad

FST1 FST2 FST3 FST4 Injection Demi-tour Ampli Ampli Ampli Ampli M1 M1 M2

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Solid State Heat Capacity Laser*

  • 2006 : 67 kW using 5 ceramic Nd:YAG slabs, 10 cm aperture
  • average output power in a ½ second burst mode, 500 microsecond pulse

width, 200 Hz

  • Efficiency not known
  • Beam quality not known but 2 x DL at 10 kW. How much at 67 kW ?
  • Main trouble : pump uniformity of the diode arrays
  • *R.YAMAMOTO SPIE, 6552, 655205 (2007)
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Disk Laser Face-pumped by 2D-stack Diode Arrays*

  • 27 kW pump power per disk (6.75 J) at

400 Hz (10% duty cycle) => 2.7 kW average power

  • Diode efficiency at 120 A = 50%
  • 1 to 5 disks : 40 mm Nd:YAG
  • Typical 26% optical efficiency at 3.24

kW output (5 disks) with 8x DL

  • C. TANG et al, SPIE, 7131, 713113 (2009)
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Conclusion /1

  • None of the diode-pumped solid-state lasers have been able to

reach the kW level (100 J @ 10 Hz)

  • DPSSL nearby the kW level have a moderate efficiency (<5 %) lower

than expected

  • Flash lamp pumped fusion lasers are still in the run with a low

efficiency (0.5 to 1%) – But can access > 85% SHG/THG

  • A flash lamp pumped amplifier with flow-cooled plates can run at 1

shot/mn – At low efficiency – 200J frequency doubled flash lamp pumped laser

  • High average power is an engineering problem :

– Solve the thermal problem at first – Optimize the heat exchange coefficient – Work at low temperature

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Conclusion /2

  • Use adaptive optics (deformable mirrors associated with pinholes) =>

better M2 factors

  • Cool the amplifier medium to cryogenic temperature => increase optical

efficiency and thermo-mechanical properties – Cryogenic temperature : at 77 K, the thermal conductivity of un-doped YAG is greater than 70 W/m.K (almost 7 times the 300 K value). Some early data were close to 100 W/m.K – According to D. Brown, the extractable power can be increased by a factor 4 to 5 between 300 and 77 K but the typical heat flux coefficient h fall in the range 1-10 W/cm2.K for water cooling at room temperature and is a little bit less for liquid N2 at 77K.

  • Use wide angular acceptance crystals => access high frequency conversion

with moderate M2 factors

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References

  • J. EMMETT et al, “The potential of high-average-power solid state lasers”, UCRL 53571, LLNL (1984)

D.C. BROWN, “Ultrahigh-average_power diode-pumped Nd:YAG and Yb:YAG Lasers,” IEEE J. Quantum Electron., 33, no.5 (1997)

  • W. KOECHNER, Solid-state laser engineering, 5th ed., Springer, Ed., (1999).
  • T. NUMAZAWA, O. ARAI, Q. Hu and T. Noda, “Thermal Conductivity Measurements for Evaluation of

Crystal Perfection at Low Temperatures,” Meas. Sci. Technol. 12, 2089-2094 (2001) D.C. BROWN, “The Promise of Cryogenic Solid-State Lasers,” IEEE J. Sel. Topics Quantum Electron., 11, no.3 (2005) R.M. YAMAMOTO et al, “Evolution of a Solid State Laser,” Proc. of SPIE, vol. 6552, 655205 (2007) T.Y. FAN et al, “Cryogenic Yb3+-Doped Solid-State Lasers,” IEEE J. Sel. Topics Quantum Electron., 13, no.3 (2007) D.C. BROWN et al, “Kilowatt Class High-Power CW Yb:YAG Cryogenic Laser,” Proc. of SPIE, vol. 6952, 69520K (2008)

  • C. TANG et al, “High-Average Power Disk Laser Face-pumped by 2D-stack Diode Arrays”, Proc. of SPIE,
  • vol. 7131, 713113 (2009)

S.G. GRECHIN and P.P. NIKOLAEV, “Diode-side-pumped laser heads for solid-state lasers”, Quantum Electronics 39 (1) 1-17 (2009)

  • B. Le Garrec (2014) High Power Laser Science and Engineering, volume 2, e28

doi:10.1017/hpl.2014.33

  • T. Ditmire et al (2014), CLEO 2014, Technologies for high intensity (STU3F),

doi:10.1364/CLEO_SI.2014.STu3F.1