ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 Interferometric beam combination Gérard Mourou.

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1 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 Interferometric beam combination Gérard Mourou

2 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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 architecture:parallel bundle or 4p arrangement – Control of the CEP.

3 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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 [arXiv:0705.2775] Diffraction limit is taken into account automatically Effectively,  1 corresponds to a contracting wave geometry or to collision of several tightly focused beams. .16  0.41  0.7

4 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 Interferometric Beam Combining Pump 23

5 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 19 mars 2009 CEA - Établissement public de recherche à caractère scientifique, industriel et commercial R.C.S. PARIS B 775 685 019 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

6 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 19 mars 2009 CEA - Établissement public de recherche à caractère scientifique, industriel et commercial R.C.S. PARIS B 775 685 019 Rôle du miroir segmenté Mise en phase de la mosaïque de faisceaux

7 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 19 mars 2009 CEA - Établissement public de recherche à caractère scientifique, industriel et commercial R.C.S. PARIS B 775 685 019 Concept du miroir segmenté 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 1mm PZT asservi sur capteur capacitif Capteur capacitif Cadre segment

8 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 Interferometric Beam Combining Pump

9 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 Beam Unbalance / Two basic effects Thermal effects Polarazibility-population difference

10 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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 DL~< 410-6cm

11 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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

12 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 Change of crystal optical length due 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 Ti:sapphire (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%.

13 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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.

14 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 ELI Industrial Challenges Opportunities and Bottlenecks of Extreme High Intensity Pulse Laser Overview Gérard Mourou

15 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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.

16 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 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

17 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010 High Peak power and high Average Power Experiment: how to accommodate high repetition rate with high level of radiation? Vacuum technology Clean room

18 ELI Nuclear Physics meeting, Bucarest Feb1-2, 2010

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