1. Relativistic Surface High Harmonic Generation
A route to intense attosecond pulses ?
Christian Rödel, Silvio Fuchs, Martin Heyer, Oliver Jäckel, Gerhard G. Paulus
FSU Jena, Institut für Optik und Quantenelektronik, Helmholtz Institut Jena
Michael Behmke, Toma Toncian, Dirk Hemmers, Mirela Cercez, Monika Toncian, Georg Pretzler, Oswald Willi
HHU Düsseldorf, Institut für Laser- und Plasmaphysik
Daniel an der Brügge, Alexander Pukhov
HHU Düsseldorf, Institut für Theoretische Physik

2. Attosecond science - Introduction
Hentschel et al.: Attosecond metrology, Nature 2007
shortest attosecond pulses: 80 as
E. Goulielmakis et al. Science, 320, 1614 (2008)

3. High harmonic generation in gases
3-step model: (a) ionization, (b,c) motion of the free electron in the laser field, (d) recollision
Corkum, Krausz: Attosecond science, Nature 2007

4. High Harmonic Spectra HHG spectrum in Neon, 50 fs, 1014 W/cm²
Agostini, DiMauro: The physics of attosecond light pulses, Reports on Progress in Physics

5. But… … laser pulses were getting stronger
Small-scale TW laser systems, Ti:Sapphire 800nm, 10 Hz
JETI IOQ: 27 fs, 800mJ
ARCTURUS ILPP: 27 fs, 2.5 J
30% of laser energy in a 7µm2 focus
I=1020 W/cm2

6. What happens at an ideal surface at Relativistic intensity ?
Corkum, Krausz: Attosecond science, Nature 2007

7. Relativistic surface High harmonic generation
PIC simulation with LPIC
JETI laser parameters: a0=4.5, t=80fs, ° p-pol incidence lambda/20 scale length
oscillating plasma vacuum boundary

8. Relativistic surface High harmonic generation
intensity
harmonic number

9. Steep density gradient – high contrast laser pulses

10. High contrast laser pulses – plasma mirror

11. High contrast laser pulses - Plasma mirror

12. High contrast laser pulses - Plasma mirror

13. High contrast laser pulses - scale length

14. Experimental setup @ arcturus

15. Diagnostics - XUV Spectrometer

16. Experimental spectra with different contrast

17. Experimental spectra with different contrast

18. Where does the modulation come from?
space / wavelength

19. Where does the modulation come from?
space / wavelength

20. … Unequal temporal spacing of the attosecond pulse train ?
sdf
superposition of attosecond pulses emitted at times tk with assumed identical shape
spectrum is given by the absolute square of the Fourier transform
plasma surface motion can be approximated by a simple parabola,
which corresponds to a linear chirp with emission times

21. … Unequal temporal spacing of the attosecond pulse train

22. … Unequal temporal spacing of the attosecond pulse train…
… describes the spectral modulations
indirect evidence of attosecond time structure of relativistic surface harmonics !!!
And just as a outlook …

23. … according to the same Pic simulations ...
… they are very short (100as)

24. Thank you for your attention