A route to intense attosecond pulses ?

RELATIVISTIC SURFACE

HIGH HARMONIC GENERATION

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 WilliHHU Düsseldorf, Institut für Laser- und Plasmaphysik

Daniel an der Brügge, Alexander PukhovHHU 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

Corkum, Krausz: Attosecond science, Nature 2007

• 3-step model: (a) ionization, (b,c) motion of the free electron in the laser field, (d) recollision

HIGH HARMONIC SPECTRA

• HHG spectrum in Neon, 50 fs, 1014 W/cm²Agostini, 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, 800mJARCTURUS laser @ ILPP: 27 fs, 2.5 J

30% of laser energy in a 7µm2 focus

I=1020 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

harmonic number

inte

nsi

ty

STEEP DENSITY GRADIENT – HIGH CONTRAST LASER PULSES

main pulseuncompensated spectral phase10 - 10-3 -6pre-pulses

10 - 10-3 -6

amplified spontaneous emission10-8

post-pulses10 - 10-2 -6

10 ps100 ps500 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

scale length at critica l density :

EXPERIMENTAL SETUP@ ARCTURUS

DIAGNOSTICS -XUV SPECTROMETER

EXPERIMENTAL SPECTRAWITH DIFFERENT CONTRAST

EXPERIMENTAL SPECTRAWITH DIFFERENT CONTRAST

WHERE DOES THE MODULATION COME FROM?

space / wavelength

WHERE DOES THE MODULATION COME FROM?

space / wavelength

sdf

… 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

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