ELI Summer School Lasers

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Ladislav Bartoš
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1 ELI Summer School, 2015 Projekt: Výzkum a vývoj femtosekundových laserových systému a pokročilých optických technologií (CZ.1.07/2.3.00/ ) ELI Summer School Lasers Jonathan Tyler Green Institute of Physics of the Czech Academy of Sciences

2 Lasers at ELI Section Energy / pulse length Rep. rate Peak power Expected max. focused intensity L1 100 mj / 20 fs 1 khz 5 TW Wcm -2 L2 10 J / 20 fs 10 Hz 0.5 PW Wcm -2 L3 30 J / 25 fs 10 Hz 1.5 PW >10 22 Wcm -2 L4 1.5 kj / <150 fs Hz 10 PW >10 23 Wcm -2

3 Principle of laser operation mirror Amplifying medium mirror

4 Single mode laser mirror Amplifying medium mirror

5 Diode Lasers Image: photonicssociety.org 1.5 Intensity 1 E n = 3.4 Image: Brittanyspears.ac 0 n = x (microns)

6 Diode Lasers

7 Diode Lasers Applications of diode lasers Spectroscopy research CD, DVD, printing technology Materials Processing Optically pumping solid state / fiber lasers

8 Fiber Lasers Figure: University of Southampton Optoelectronics Research Center

9 Solid State Lasers Solid State Laser Image: Lambda Optics Image: QRBiz

10 Solid State Lasers Titanium Sapphire Image: Laser Quantum Image: Wall, Sanchez, Lincoln Lab Journal, 3 (1990)

11 Neodymium-doped materials Solid State Lasers Nd:YAG Energy level diagram

12 Neodymium-doped materials Solid State Lasers

13 Solid State Lasers Ytterbium-doped materials Smaller quantum defect and larger amplification bandwidth than Nd-doped materials

14 Efficient cooling in SS lasers 10 Hz rep. rates Pulse energy 10J khz rep. rates kw average power 10 Hz rep. rate High pulse energy >100J multislab Courtesy T. Metzger (MPQ Garching) Courtesy K. Ertel and J. Collier (RAL/STFC)

15 SS and Fiber Lasers Applications of diode lasers LIDAR Defense Machining / Materials Processing Ultra-fast science High field physics

16 Mode locking =

17 Mode locking

18 Mode locking: Kerr Lens Saturable Absorber Keller, Nature 424, (2003) Precision Dimensional Metrology based on a femtosecond pulse laser, DOI: /7950

19 Amplification methods To amplify ultra-short pulses it is necessary to 1. Amplify all wavelengths 2. Control the relative phase of all wavelengths

20 Amplification methods Extremely high peak intensities of short pulses will destroy amplifier material. How can we amplify the pulses? Chirped Pulse Amplification (CPA)

21 Amplification methods Chirping a pulse is a method for stretching the pulse in time and decreasing the peak pulse power.

22 Amplification methods Stretcher Amplifier Compressor

23 Temporal dispersion β ω = ω n(ω) c β ω = β ω o + β ω ω ω o L 2 β ω 2 ω ω o 2 + Related to phase velocity Inverse group velocity

24 Temporal dispersion β ω = ω n(ω) c β ω = β ω o + β ω ω ω o L 2 β ω 2 ω ω o 2 + Related to phase velocity Inverse group velocity Group velocity dispersion (GVD)

25 Temporal dispersion Number of higher order dispersion terms to account for depends on bandwidth of optical pulse. ps pulses: track up to TOD fs pulses: track up to fifth order or higher

26 Bulk Material: n = n(ω) Stretchers / Compressors

27 Chirped Mirrors Stretchers / Compressors

28 Control GDD and TOD with incidence angle and grating separation Stretchers / Compressors

29 L1 kw compressor

30 L1 kw compressor

31 OPCPA Titanium Sapphire Amplification methods Used in L3 Used in L1, L2

32 OPCPA Optical Parametric chirped pulse amplification Requirements for phase matching: Signal E p = E s +E i Pump k p = k s + k i Idler

33 OPCPA Broad phase matching bandwidth in non-collinear configuration α θ Crystal optical axis k p k s k i Bandwidth of signal

34 Phase Matching Angle (deg) OPCPA Broad phase matching bandwidth in non-collinear configuration Phase matching in BBO crystal Pump: 515nm Signal: ~800nm Optimum phase matching angle p = 515 nm, Material: 3, Phase Matching Type: 1 = 2.25 o = o = 2.5 o = o = 2.75 o (nm)

35 OPCPA OPCPA is less developed than Ti:Sapphire amplification, but offers important advantages: 1. Very large amplification bandwidth 2. No energy stored in crystal (no heating due to quantum defect) 3. No amplified spontaneous emission; however parametric super-flourescence can occur

36 Example: L1 laser system Thin Disk Regenerative Amplifier Compressor + SHG 1030 nm Oscillator Broadband 800 nm OPCPA

37 Example: L1 Thin disk lasers Pump laser: 1kHz

38 Autocorrelation trace (AU) 515 nm pulse energy Efficiency Example: L1 Thin disk lasers Compressor efficiency: 90.5% pulse duration: 1.8 ps data fitted curve 56% conversion efficiency giving 16 mj at 515 nm t (ps) nm pulse energy

39 Example: L1 Thin disk lasers Second Harmonic Generation in LBO

40 Example: L1 Thin disk pumped OPCPA Pulses synchronized to 14 fs RMS. Loop is robust and remains locked for hours. F. Batysta, et al., Opt. Exp., 22, (2015)

41 L2 Beamline Špičkový výkon Energie v pulsu Délka pulsu Výstřelů 1 PW (15 nul) 15 J 15 fs 10 / vteřinu Dodavatel Tým ELI + Rutherford Appleton Laboratory Kryogenně chlazený čerpací 10 J laser pro OPCPA Technologie Diodové čerpání, OPCPA 120 mm Yb:YAG monokrystal firmy Crytur

42 L3 Beamline Špičkový výkon 1 PW (15 nul) Energie v pulsu 30 J Délka pulsu 30 fs Výstřelů 10 / vteřinu L3 Front end Diodami čerpané Nd:sklo čerpací laser Ti:safírový zesilovač Diagnostika svazku Dodavatel Technologie Livermore National Energetics + Tým ELI Čtvercový svazek 214mm x 214mm, Ti:safírové zesilovače a diodové i Nd:skleněné čerpací lasery Front end, Ti:safírový oscilátor, stretcher,... PW kompresor a diagnostika

43 L4 Beamline Špičkový výkon Energie v pulsu Délka pulsu Výstřelů Dodavatel Technologie 10 PW (16 nul) 1,5 kj a 150 J 1 ns a 150 fs 1 / minutu National Energetics + Ekspla + Tým ELI Výbojkově čerpané Nd:skleněné zesilovače + OPCPA předzesilovač

44 Thank you for your attention! Thanks to Lasers & Control Team Pavel Bakule Roman Antipenkov Jakub Novak Frantisek Batysta Robert Boge Jack Naylon Tomas Mazanec Martin Horacek Marc-Andre Drouin

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