Development and perspectives of high repetition rate attosecond sources C.L. Arnold1, A. Harth1, M. Miranda1, P. Rudawski1, J. Guo1, C. M. Heyl1, E.W. Larsen1, E. Lorek1, E. Mårsel1, A. Mikkelsen1, E. Månsson1, M. Gisselbrecht1, S. Ristinma-Sörensen1, J. Matyschok2, O. Prochnow2, T. Binhammer2, U. Morgner2 J. Mauritsson1, A. L’Huillier1 1Department 2VENTEON of Physics, Lund university, Sweden Laser Technologies GmbH, Hertzstr. 1b, 30827 Garbsen, Germany * Email: [email protected] Characteristic time and length scale 10 8 10 10 10 4 10 6 Atom 10 2 100 C. elegans Virus 10 2 10 20 Length / m Building Mouse Galaxi Small molecule Human Bacteria Macromolecule Drosophila Time / s 10 15 Attosecond pulses 10 12 Picosecond laser Femtosecond laser 10 4 10 8 Flash lamp Q-switched laser High speed camera Free electron laser Synchrotron 100 101 Camera 10 2 1012 Telescope Overview • Generation of attosecond pulses • Motivation for high-repetition rate attosecond sources • Few-cycle, CEP-stable OPCPA laser source • High-repetition rate attosecond source • Conclusion and outlook HHG – a strong field effect 2. Acceleration Laser field 2 1 3 Electron trajectories 3. Recombination Return Energy (UP) 1. Tunneling Cut-off ~IP+3.2 UP Short Long Return Time (T1) Corkum, Phys. Rev. Lett., 71:1994 (1993). Schafer et al, Phys. Rev. Lett., 70:1599 (1993). Lewenstein et al, Phys. Rev. A, 49:2117 (1994). Time <-> Frequency XUV E-Field and trajectories E(t) ”Inversion symmetry” or ”Electron interferences” or ”Pulse-to-pulse interferences” XUV T/2 Time (fs) => Odd harmonics. 2w Principle of an attosecond science experiment Train of attosecond pulses or single attosecond pulse Femtosecond laser source Detector Time High-order harmonic generation in a gas Applications: Frequency - Attosecond spectroscopy - Time-resolved electron microscopy - ... Discrete high-order harmonics or continuous XUV spectrum Motivation for high repetition rate attosecond source Attosecond science – low vs. high repetition rate Probing single ionization Probing electron correlation Detector Detector By coutesy of J.M. Dahlström Klünder et al., Phys. Rev. Lett., 106:143002 (2011). Guenot et al., Phys. Rev. A, 85:053424 (2012). Månsson et al, Nature Phys. 10:207 (2014). Attosecond science – low vs. high repetition rate Probing single ionization Probing electron correlation 2d- Correlation map Detector Detector Detector Energy Klünder et al., Phys. Rev. Lett., 106:143002 (2011). Guenot et al., Phys. Rev. A, 85:053424 (2012). Kinetic energy sum Count Photo-electron spectrum Low kinetic energy Månsson et al, Nature Phys. 10:207 (2014). Applications benefitting from a high-repetition rate attosecond source Correlations in multi-electronic systems - Coincidence detection schemes - 3d electron momentum Attosecond time-resolved electron microscopy - attoPEEM Detector Coincidence detection Nano-structures, Nano-devices M.I. Stockman et al., Nature Photon. 1:539—544 (2007). Mikkelsen et al, Rev. Sci. Instrum., 80:123703 (2009). Mårsell et al, Ann. Phys., 525:162 (2013). Principle of photoemission electron microscopy Image formation in the Focus IS-PEEM. • Electrons are photo-emitted from the surface and accelerated by a 10-15 kV voltage. • Zero, one or two projective lenses can be used. • The signal is amplified and projected onto a fluorescent screen. • Resolution down to 20 nm. Development of an OPCPA based, high repetition rate attosecond source CPA vs. OPCPA Chirped pulse amplification Pump From oscillator Compressor Stretcher Amplification crystal Optical parametric chirped pulse amplification From oscillator Compressor Idler Stretcher Nonlinear crystal Short pulse laser development has reached at a crossroads CPA vs. OPCPA technology CPA • Leading technology since 25 years for shortest and most energetic pulses • • • • Challenges: Thermal management Thermal lensing Gain-bandwidth narrowing Reaching below 20fs is complicated • • • • Benefits: Very well developed technology Commercially explored Easy to achieve very high pulse energy Simple Q-switch pump-laser technology Solutions: • Cryo cooling • Intra- and extra-cavity spectral shaping OPCPA • Demonstrated in 1992, but it took until recently for the technology to mature Challenges: • Elaborate pump laser technology: often Yb-based, all-diode pumped fiber or thindisk CPA lasers; usually not commercially available. • Synchronization between pump and signal pulses • • • • • Benefits: Energy transfer between pump and seed pulses is nonlinear • No energy stored in the crystal Easily scalable to high repetition rate Broad amplification spectrum Wavelength not fixed to specific materials Compact design, good CEP stability High-repetition rate OPCPA 80 MHz 200 kHz Fiber based pump laser @1030nm 27 µJ 100 µJ 115 µJ 44 µJ Ultra-broadband, 80 MHz, 2 nJ CEP-stable Oscillator Two-stage NOPA 80 MHz 200 kHz f:2f 10 µJ, < 7 fs, 200 @kHz J. Matyschok et al., Opt. Express 21: 29656 (2013). Ultrashort pulse characterization Spectrometer SHG crystal V.V. Lozovoy, Opt. Lett., 29(7):775 (2004). M. Miranda et al., Opt. Express, 20(1):688 (2012). M. Miranda et al., Opt. Express, 20(17): 18732 (2012). Ultrashort pulse characterization General optimization problem: minimize an error function “measured” guess spectral phase until 2D trace is reproduced minimize rms error Compare chirped mirror compressors Old chirped mirror set New chirped mirror set Commercialization of the d-scan High-repetition rate HHG >10 µJ, <10 fs, 200 kHz – 2 MHz CEP Challenges for HHG at high repetiton rate • Low pulse energy • Tight focusing • Large XUV divergence • High gas pressure required • Good efficiency is tough to obtain High-repetition rate HHG >10 µJ, <10 fs, 200 kHz – 2 MHz CEP dependent HHG CEP dependent HHG Region I: Change from even to odd harmonic order ? Region III: Odd order harmonics, but amplitude changes Region II: Harmonics are split and shifted - complex behavior ? Model: Multi-pulse interference Short driving pulse 𝝋𝑪𝑬𝑶 Transmission Analogy to a multipath interferometer 0 2p Saleh, Teich, Fundamentals of Photonics, Wiley (2007). Time Attosecond pulse train 4p 6p j CEP dependent HHG Measurement Simulation Clear CEP effect in different regions Conclusion and outlook • OPCPA laser technology allows for high power and highrepetition rate, CEP-stable, few-cycle laser sources • High repetition rate attosecond source was realized • Perfect conditions for – Studying correlations in multi-electronic systems – Attosecond time-resolved electron microscopy • Laser upgrade is being conducted right now • New developments: – MIR OPCPA laser based on thin-disk pump technology – Soft-X-ray attosecond source for core-hole spectroscopy and element specific, time-resolved imaging Atto-PEEM @ 200 kHz CPA 1kHz @1 kHz @200 kHz Exposure time 400 s Resolution < 900 nm x 10 x3 30 s < 350 nm OPCPA 200kHz Lund group for Attosecond Science A. L’Huillier, C.L. Arnold, J. Mauritsson, M. Miranda, A. Harth, E.W. Larsen, C. Heyl, E. Lorek, P. Rudawski, C. Guo, A. Losquin Synchrotron Radiation Physics M. Gisselbrecht, E. Månsson, A. Mikkelsen, E. Mårsell, S. Sörensen VENTEON and University of Hannover T. Binhammer, O. Prochnow, J. Matyschok, U. Morgner
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