Interferometric beam combination

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Interferometric beam combination

• Gérard Mourou

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Why interferometric beam combination?

• While maintaining higher peak power, it provides
  a way to
• Enhance cooling,
• Decrease the confocal volume significantly,
• Decrease optics size,
• Flexibility on beam architectureparallel bundle
  or 4p arrangement
• Control of the CEP.

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Reaching the highest Intensity Moving to a
Spherical wave
Focal radius
Exact solution for arbitrary ? A.M. Fedotov,
K.Yu. Korolev, M.V. Legkov, SPIE Proceedings
Vol. 6726, 672613, 2007 arXiv0705.2775
Diffraction limit is taken into account
automatically
??.16
??0.41
??0.7
Effectively, ??1 corresponds to a contracting
wave geometry or to collision of several
tightly focused beams.
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Interferometric Beam Combining
Pump
Pump
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Phasing Gratings
Mosaïque de faisceaux type PETAL Les réseaux ne
sont pas dans un même plan, ils sont installés
sur des supports individuels. Des réglages tilts
et piston sont possibles mais il faut combiner
grandes courses et sensibilités, le tout
fonctionnant sous vide
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Rôle du miroir segmenté
Mise en phase de la mosaïque de faisceaux
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Concept du miroir segmenté
1mm

• Un cadre supporte les 4 segments
• Chaque segment est maintenu en trois points
• Le positionnement suivant Z est assuré au niveau
  de chacun des 3 points par un vérin piézo
• Un capteur capacitif mesure la position en Z de
  la face avant du segment en regard de chaque
  vérin
• Chaque vérin est asservi en continu sur la mesure
  du capteur

Capteur capacitif
PZT asservi sur capteur capacitif
segment
Cadre
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Interferometric Beam Combining
Pump
Pump
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Beam Unbalance / Two basic effects

• Thermal effects
• Polarazibility-population difference

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Beam Interferometric Balance

• ? Thermal expansion
• Because the heat dumped in the crystal is
  only
• .5J/cm3 for a crystal length of 5cm and a
  fluence of 2J/cm3.
• DT .05 C, corresponding to
• DLlt 410-6cm

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Thermal expension
The pump is only 30ns, so it will take effect
after 20 microseconds.The time for the sound to
propagate across the crystal. What counts is the
difference between two pump beams in energy. This
difference is 2. The conclusion is that the
beam to beam optical path Difference after the
pump is a very small fraction of the wavelength,
i.e. 1 . The
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Change of crystal optical lengthdue to
electronic level population

• Refractive index change, accompanies the change
  in population of electronic levels.
• This effect unlike the thermal refraction is very
  prompt. It will follow the pump and the laser
  signal as the beam.
• Calculation for small gain of 100 in Tisapphire
  (O. Antipov), shows that it is of a wave. This
  effect will be of the order of a wave /50 for a
  beam unbalance of 2.

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CEP
In the case of interferometric addition the CEP
should not be a question because CEP come from
the difference between phase velocity and group
velocity.
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ELI Industrial ChallengesOpportunities and
Bottlenecks of Extreme High Intensity Pulse
LaserOverviewGérard Mourou
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High Peak power and high Average Power

• How can we get high peak power plus average power
  
• By the choice of the amplification technique
• CPA or OPCPA or Hybrid CPA-OPCPA
• Choice of pumping material
• Choice of the pumping System flash lamp, diode.

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High Peak power and high Average Power

• Choice of the architecture single beam or
  mutiple beams better cooling, smaller optics,
• In the case of multiple beams we will need
  interferometric addition It will provide smaller
  optics, better cooling, smaller volume of
  interaction
• Interferometric addition will solve the problem
  of CEP.
• Higher damage threshold

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High Peak power and high Average Power

• Experiment
• how to accommodate high repetition rate with
  high level of radiation?
• Vacuum technology
• Clean room

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