relativistically oscillating plasma surfaces : high harmonic generation and ultrafast plasma...
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Relativistically oscillating plasma surfaces : High harmonic generation and ultrafast plasma
dynamics
Brendan Dromey
ICUIL 26 Sept – 1 Oct Watkins Glen NYBrendan Dromey [email protected]
Acknowledgements
Brendan Dromey [email protected]
Experiments: PIC-Simulations:• R. Hörlein• Y. Nomura• D. Kiefer• P. Heissler• G. D. Tsakiris
• S. Rykovanov
Max Planck Institute for Quantum Optics
IESL, FORTH, Heraklion Crete:
• P. Tzallas• D. Charalambidis
Queens University Belfast:
• M. Yeung• D. Adams • M. Geissler• M. Zepf
ICUIL 26 Sept – 1 Oct Watkins Glen NY
LANL, Trident
• D. Jung• B. M. Hegelich
STFC Central Laser Facility
• P. Foster• C. Hooker• D. Neely • P. Norreys
Outline
• Low and high contrast interactions
• High order harmonic generation (HOHG) from solids
• keV harmonic generation
• Role of surface roughness – ultrafast laser driven plasma dynamics
• Divergence of HOHG
• Novel results for HOHG transmitted through thin foils scaling in the relativistic limit
[email protected] 26 Sept – 1 Oct Watkins Glen NYBrendan Dromey
Contrast in a laser system
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Slide courtesy of R. Marjoribanks
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Contrast improvement in a laser system
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AR coated
Contrast increased by ~102 per plasma mirror used
1014 to 1015 Wcm-2
Plasma mirror
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Petawatt class interactions
Brendan Dromey [email protected]
Andor CCD detector
Target – CH (5-10 nm rms)
Double plasma mirrorIncident laser pulse: f3 cone
Vulcan Petawatt at RAL: ~600J in 500fs ~ 1053nm
1200 lines per mm flatfield grating
Gold collection mirror
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Low Vs high contrast
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Spectrum with plasma mirror – High harmonic generation, scaling in the relativistic limit
B. Dromey et. al., Nature Physics, 2, 456 (2006)
Spectrum with no plasma mirror
7mm
17nm ~2nm
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Relativistically oscillating plasmas
Brendan Dromey [email protected]
• The target surface is highly ionised by the leading edge of the pulse – becomes rapidly over dense (reflecting to incident radiation)
• The collective electron motion created by the incident electromagnetic wave can be considered as an oscillating mirror
Incident pulse
Reflected pulse
Oscillating critical density surface
Illustration from George TsakirisNew Journal Physics 8, 19, 2006
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Einstein's Relativistic Doppler effect - 42
Oscillatory extension to Relativistic Doppler effect
γs
t´
vs
c
t´
cvs
Universal spectrum381 nIn
Extended Roll-over
nmax 81/2 3
T. Baeva, S. Gordienko, A. Pukhov, Phys. Rev. E, 74, 046404 (2006)
Relativistic Spiking
Brendan Dromey [email protected] 26 Sept – 1 Oct Watkins Glen NY
= n-2.66
Important properties of ROM
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•Phase locked to driving laser – no phase matching required
•Both odd and even orders generated
•Generation process saturates in the relativistic limit
•High conversion efficiency – scaling as n-2.66, where n is harmonic order
•Harmonic width greater than separation for keV energies
•Rapid scaling to high orders with driving laser intensity
•Filter to obtain train of attosecond pulses
•No chirp
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Coherent wake emission
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Plexiglass Target (Density ~1.3 g/cm^3):Glass Target (Density ~2.6 g/cm^3):
1113 121417 1516 1113 121415
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Brunel electrons
Relativistic plasma harmonics – salient results
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~p
26 24 22 20 18 16 14 Harmonic order (n)
ROM
Individual pulse duration: 900 400 as
Attosecond Phase LockingDiffraction limited performance
From ‘Y. Nomura et al, Nature Physics, 5, 124 - 128 (2009)
From ‘B. Dromey et al, Nature Physics, 5, 146 - 152 (2009)
Exceptional coherence properties of the driving laser transferred to the XUV
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Petawatt class interactions
Brendan Dromey [email protected]
Image plate detector
Target – CH (5-10 nm rms)
Double plasma mirrorIncident laser pulse: f3 cone
Vulcan Petawatt at RAL: ~600J in 500fs ~ 1053nm
Mica crystal,
Von Hamos geometry
ICUIL 26 Sept – 1 Oct Watkins Glen NY
ROM harmonics – Petawatt class
Brendan Dromey [email protected]
keV ROM harmonics and the efficiency roll-over
B. Dromey et al., Phys. Rev. Lett. 99, 085001 (2007)
10
1
10-1
10-2
Inte
nsity
/arb
. uni
tsN
orm
alis
ed a
t 120
0th o
rder
Harmonic order, n1500 3000
a) (1.5±.3)1020Wcm-2
b) (2.5±.5)1020Wcm-2
Photon Energy, keV
2000 2500
1770 2360 2950 3530
p=2.8
p=2.4
Prel=2.55 (+0.25, -0.15)
namax> 2600
nbmax>3000
Intensity dependent rollover
Focused Int
Prel
n-p
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How can we see keV harmonics?
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DfSurface roughness - Fourier analysis
Angstrom wavelength lengths beamed from nm roughness targets?
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Motion under the influence of normally incident, linearly polarized EM wave, bound to an immobile ion background via charge separation fields
4 cycles FWHM Gaussian pulse, ao= 10 , ne = 400nc
Density gradient from 1-D
PIC, same parameters
Electron capacitor model
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Complete discussion given in: Rykovanov et al arXiv:0908.3134v2 [physics.plasm-ph]
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Brendan Dromey [email protected]
L =800nm, 4 cycle pulse, h = 40nmm, a0 =5 (corresponds to > 1019Wcm-2)
Snap shots from Simulation – over a single cycle in the rise of the pulse
Ultrafast plasma dynamics: 2-D PIC simulations
Complete discussion given in: Rykovanov et al arXiv:0908.3134v2 [physics.plasm-ph]
h
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Brendan Dromey [email protected]
23242526 22 21 20 19 18 17 16 15 14
GratingAu Mirror
Detector
HOHG Source
Astra laser at RAL: 10Hz ~1.5J in 40fs ~ 800nm
Astra at RAL: 10Hz ~1.5J in 40fs ~ 800nm
Off-axis emission CWE only
On-axis emission - CWE and RomO- axis emission - Rom only
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Insensitivity to surface roughness
Brendan Dromey [email protected]
From ‘B. Dromey et al, NATURE Physics, 5, 146 - 152 (2009)
22 20 18 16Harmonic Order
37 35 33 31 29 27 25 23
Coun
ts (
104 )
2
1
0.5
1.5
Harmonic Order
x
y rms <1nm
rms ~18nm
38
Spectra same to within 1 standard deviation for factor of >10 increase in roughness
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Divergence of HOHG
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Harmonic Spectra: total power emitted
10
1
10-1
10-2
Inte
nsity
/arb
. Uni
ts N
orm
alis
ed a
t 120
0th o
rder
Harmonic order, n1500 3000
a) (1.5±.3)1020Wcm-2
b) (2.5±.5)1020Wcm-2
Photon Energy, keV
2000 2500
1770 2360 2950 3530
Prel=2.55 (+0.25, -0.15)
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Harmonic divergence
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Flat surface
Harmonics emitted with intrinsic divergence
If all orders diffraction limited - expect a much flatter spectrum
θ
L
θL/n
Diffraction limited peformance would suggest harmonic~Laser/n harmonic~10-4 rad for keV harmonics.
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Uniform harmonic divergence
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Curved surface
Harmonics emitted with divergence given by the curved surface
D
-All orders identical divergence-Beam still focusable to diffraction limitfor spherically bent surface.
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Divergence measurements
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Grating
Detector
Source
On axis
Grating
Detector
Source
On axis
-1nm
1nma) <1nm rms i) Orders 17-39
Spectrometer configuration Recorded spectra
Angle (mrad)
39th (~20.5nm )
20th (~40nm)
19mrad 1/e2
a) b)
-60 -40 -20 0 20 40 60
0.1
0.3
0.5
0.7
1.1
20
10
30
40
Angl
e
(mra
d)
Wavelength (nm)
CWEordersROM
orders
Inte
nsity
, arb
. uni
ts
Diffraction limited divergence
20 25 30 35 40 45 50
B. Dromey et al, Nature Physics, 5, 146 - 152 (2009)
ICUIL 26 Sept – 1 Oct Watkins Glen NY
ROM in transmission:
H. George, et al., NJP, 9, 113028 (2009)
Experimental results: K. Krushelnick, et al., PRL, 100, 125005, (2008).
ROM harmonics in transmission
Brendan Dromey [email protected] 26 Sept – 1 Oct Watkins Glen NY
targetincident
beam
MCP-detector
collectionmirror
grating
entranceslit
ROM harmonics in transmission
Shortpulse-Beam: 500fs, 125J, 250 TW (1054nm)
Trident laser - Los Alamos national labs
Brendan Dromey [email protected] 26 Sept – 1 Oct Watkins Glen NY
ROM harmonics in transmission
Brendan Dromey [email protected]
23rd
33rd
Detector position 1Detector position 2
17nm
Al L-edge
61st
53rd
43rd
26nm 45nm
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Raw data from CCD
Brendan Dromey [email protected] 26 Sept – 1 Oct Watkins Glen NY
ROM harmonics in transmission
Harmonic orders 24 - 60
Har
mon
ic in
tens
ity n
orm
alis
ed t
o th
e 33
rd h
arm
onic
125 and 200nm Diamond like carbon
Recall from the theory of relativistic
spikes efficiency scaling is expected
as
n-2.66
ROM harmonics the full picture
Brendan Dromey [email protected] 26 Sept – 1 Oct Watkins Glen NY
B. Dromey et. al., Nature Physics, 2, 456 (2006)
Harmonic orders 24 - 60
Ha
rmo
nic
inte
nsi
ty n
orm
alis
ed
to
th
e
33rd
ha
rmo
nic
Ha
rmo
nic
inte
nsi
ty n
orm
alis
ed
to
th
e
23
8rd h
arm
on
ic
Ultrathin thin foil at solid density
ROM harmonics for radial density profiling
Brendan Dromey [email protected] 26 Sept – 1 Oct Watkins Glen NY
Red triangles on Figure
For more detail:
Rainer HoerleinThursday 11:00am
Experimental geometry
200nm
80nm
Summary
Brendan Dromey [email protected]
•Very high harmonics possible from the relativistic plasma medium
•Diffraction limited performance and attosecond phase locking
•Ultrafast laser driven plasma dynamics – allows beamed keV radiation
•Target denting – possible to shape targets to control divergence
•Transmitted HOHG – novel ROM source
•Use as an ultrafast broadband density diagnostic
ICUIL 26 Sept – 1 Oct Watkins Glen NY
Brendan Dromey [email protected]
Ultrafast broadband density diagnostic
Single foil 125nm,Slow drop in signal to higher orders (~relativistic limit scaling)
With Secondary foil (80nm)Plasma Absorption, up to plasma frequency
With secondary foil (200nm)Strong Carbon absorption
28th
23rd
45nm 30 nm
O2 17.1nm line in second order
ICUIL 26 Sept – 1 Oct Watkins Glen NY