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
ATTOSECOND SCIENCE - INTRODUCTION
Hentschel et al.: Attosecond metrology, Nature 2007
shortest attosecond pulses: 80 as
E. Goulielmakis et al. Science, 320, 1614 (2008)
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
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
BUT…
… laser pulses were getting stronger
Small-scale 10-100 TW laser systems,
Ti:Sapphire 800nm, 10 Hz
JETI laser @ IOQ: 27 fs, 800mJ
ARCTURUS laser @ ILPP: 27 fs, 2.5 J
30% of laser energy in a 7µm2 focus
20
I=10
2
W/cm
WHAT HAPPENS AT AN IDEAL SURFACE
AT RELATIVISTIC INTENSITY ?
Corkum, Krausz: Attosecond science, Nature 2007
RELATIVISTIC
SURFACE
HIGH HARMONIC GENERATION
• PIC simulation with LPIC
• JETI laser parameters:
a0=4.5,
t=80fs,
45° p-pol incidence
lambda/20 scale length
• oscillating plasma
vacuum boundary
intensity
RELATIVISTIC SURFACE HIGH HARMONIC
GENERATION
harmonic number
STEEP DENSITY GRADIENT –
HIGH CONTRAST LASER PULSES
main pulse
amplified
spontaneous
emission
-8
10
500 ps
pre-pulses
-3
-6
10 - 10
100 ps
10 ps
uncompensated
spectral phase
-3
-6
10 - 10
10 ps
post-pulses
-2
-6
10 - 10
HIGH CONTRAST LASER PULSES –
PLASMA MIRROR
HIGH CONTRAST LASER PULSES PLASMA MIRROR
HIGH CONTRAST LASER PULSES PLASMA MIRROR
HIGH CONTRAST LASER PULSES SCALE LENGTH
scalelength at critical density:
EXPERIMENTAL SETUP
@ ARCTURUS
DIAGNOSTICS XUV SPECTROMETER
EXPERIMENTAL SPECTRA
WITH DIFFERENT CONTRAST
EXPERIMENTAL SPECTRA
WITH DIFFERENT CONTRAST
WHERE DOES THE MODULATION COME
FROM?
space / wavelength
WHERE DOES THE MODULATION COME
FROM?
space / wavelength
… UNEQUAL TEMPORAL SPACING OF THE
ATTOSECOND PULSE TRAIN ?
superposition of attosecond pulses emitted at times tk with assumed identical shape
spectrum is given by the absolute square of the Fourier transform
sdf
plasma surface motion can be approximated by a simple parabola,
which corresponds to a linear chirp with emission times
… UNEQUAL TEMPORAL SPACING OF THE
ATTOSECOND PULSE TRAIN
… 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 …
… ACCORDING TO THE SAME PIC
SIMULATIONS ...
… THEY ARE VERY SHORT (100as)
THANK YOU FOR YOUR ATTENTION