High Order Harmonic Generation From Solid Targets: Towards Intense Attosecond Pulses A' Tarasevitch

1
High Order Harmonic Generation From Solid
Targets Towards Intense Attosecond Pulses A.
Tarasevitch and D. von der Linde Universität
Duisburg-Essen
2
Outline

• Introduction

• Particle-in-Cell Simulations

• Experiments on high order harmonic
• generation

• Attosecond pulses, two colour driven
• harmonics

3
Harmonics in Reflection from a Surface

• specular reflection

pulse quality is of crucial importance
V C

• moderate energy

100 mJ, 45 fs, 10 Hz

• very tight focusing

intensities I gt 1019 W/cm2
4
Interaction with a Surface
w
w nW
W w (p - pol.)
xx0cosWt
W 2w (s - pol.)
a0 ne/ncr
J. Nees et al., J. Mod. Opt. 52, 305 (2005)
S ne/(ncr a0) 1
5
1D PIC Simulations
LPIC-code (R. Lichters, J. Meyer-ter-Vehn, and A.
Pukhov)
a0 0.3, p-pol., t 20T, ne 49ncr

• L/l 0.02 strong restoring force

relativistic mechanism
5th harm.
resonant mechanism, CWE

• L/l 0.2 weak restoring force

6
Laser Beam Parameters
Third order ACF
FWHM 45 fs
1E-2 1E-4 1E-6 1E-8
norm. intensity
800 nm
-4 -2 0 2
4
delay (ps)
800 nm 400
nm
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Experimental Setup
parabolic mirror

• sharp focusing (F/3), adaptive
• optics

• conversion to 2w

• two-pulse / two colour
• experiments

• precise positioning

l 400 nm
aperture
CCD
target
Al
toroidal grating
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Harmonic Spectra _at_ 21018W/cm2, 400 nm
a0 0.5
104 103 102
p-pol.
Energy (a.u.)
wp
6 8 10 12
14
104 103 102
wp
p-pol.
Energy (a.u.)
6 8 10 12
14
Harmonic number
9
Harmonic Spectra _at_ 21019W/cm2, 400 nm
a0 1.2
p-pol.
polystyrene
6 8 10 12 14
16 18
Harmonic number
A. Tarasevitch et al., Phys.Rev. Lett. 98, 103902
(2007)
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Scale Length Dependence
p-pol.
parabolic mirror
l 400 nm
l 800 nm
aperture
CCD
target
Al
toroidal grating
A. Tarasevitch et al., Phys.Rev. Lett. 98, 103902
(2007)
11
Harmonic Divergence
12
Harmonic Efficiency (p-pol.)
Norm. intensity/energy
p
L/l0
Harmonic number
13
Attosecond Pulses
14
Attosecond Pulses Spectral Filtering
S. Gordienko et al., PRL 93, 115002 (2004), T.
Baeva et al., PRE 74, 065401 (R) (2006), G.
Tsakiris et al., NJP 8, 19 (2006)
reflected radiation
surface oscillations
w 4g2w0
frequency domain
I(w)
w/w0

• high losses due to spectral filtering
• highly relativistic regime is needed

I(t)
time domain
-1
1
t/T0
15
Super Mode Locking?
a0 1, n 49nc, L/l 0.02, Q 480
reflected Radiation frequency domain
time domain
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Pulses Expected in Experimental Conditions
a0 1, n 49nc, L/l 0.02, Q 480
reflected Radiation frequency domain
time domain
Al filter
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Atto-Pulses by resonant HOHG
a0 0.3, n 108nc, L/l 0.04, Q 480
reflected Radiation frequency domain
time domain
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Two Pulse Experiments
drive
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Two-Pulse HOHG / Atto-Pulses
n 49nc, L/l 0.02, Q 480
attosecond pulses produced by the probe pulse
driving pulse a0 3.0, 2w0 probe pulse a0
0.1, w0
up to 5 w0 up to 30 w0
driving
probe
zero-cycle atto-pulses
20
Two-Color Harmonics
frequency domain
m
l 400 nm
I400 nm 1019 W/cm2
I800 nm 1017 W/cm2
target
DT0
21
Conclusions

• plasma scale length plays an important role in
  HOHG
• efficiency
• mechanisms of HOHG
• in relativistic regime the harmonics are much
  less sensitive to the
• plasma scale length
• comparison with PIC simulations suggests that
  attosecond pulse
• trains must be already available in our
  experiments
• two colour driven harmonics may provide a way to
  high efficient
• attosecond (zero-cycle?) pulse production even
  at moderate
• pump intensities