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Relativistic Surface Harmonic Generation - Physikalisches Institut

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Relativistic Surface Harmonic Generation - Physikalisches Institut Powered By Docstoc
					          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


       I=10 20       W/cm2
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
RELATIVISTIC SURFACE HIGH HARMONIC
GENERATION
intensity




             harmonic number
STEEP DENSITY GRADIENT –
HIGH CONTRAST LASER PULSES


                    main pulse
                                  uncompensated
                                  spectral phase   post-pulses
                   pre-pulses       -3
                                  10 - 10
                                          -6         -2
                                                   10 - 10
                                                          -6

                     -3   -6
   amplified       10 - 10
   spontaneous
   emission
      -8
   10


  500 ps         100 ps   10 ps   10 ps
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

				
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