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Laser-
Laboratorium
Göttingen e.V.
Laser-Laboratorium Göttingen e.V.
Hans-Adolf-Krebs Weg 1
D-37077 Göttingen
K. Mann
J.O. Dette, F. Kühl, U. Leinhos, M. Lübbecke,
T. Mey, M. Müller, M. Stubenvoll, J. Sudradjat, B. Schäfer
Table-top EUV/Soft X-ray Source and
Wavefront Measurements at Short Wavelengths
2
Dept. “Optics / Short Wavelengths”
Beam propagation
Wavefront
coherence
M²
Optics test (351…193 nm)
(Long term) degradation (109 pulses)
Non-linear processes
LIDT
Absorption / Scatter losses
Wavefront deformation
EUV/XUV technology
Source & Optics
Metrology
Material interaction
pulsed Xenon gas jet
laser
Laser plasma source for extreme UV and soft x-ray radiation
XUV: =1…10nm EUV: = 10…20nm
• Univ. Prag
• Univ. Göttingen
• Max-Planck Inst.
~ 300µm
compact
low debris
long-term stable
versatile
4
LLG-Activities Based on
LPP Source
Direct structuring EUV reflectometry
NEXAFS spectroscopy Soft x-ray microscopy
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 8510
-4
10-3
10-2
10-1
100
Ref
lect
ivit
y
Sample angle
=2.88nm
5
Ablation / damage thresholds
@13.5nm
EUV Schwarzschild objective (Mo/Si):
~ J/cm² @ 13,5 nm
Damage thresholds of
mirrors / substrates single-pulse damage
F. Barkusky, K. Mann et al., Optics Express 18, 4347 (2010)
EUV/XUV plasma source
Isolated Nitrogen line @ = 2.88nm
Peak brillance:
6*1017 [Ph./(s mrad2 mm2 0,1%BW)]
Microscopy @ = 2.88nm
T. Salditt
Univ. Göttingen
= Near-edge x-ray absorption fine-structure
Excitation of unoccupied molecular orbitals
NEXAFS Spectroscopy in the „water window“:
„Fingerprint“ of molecules
surface-sensitive chemical analytics
2,0 2,5 3,0 3,5 4,0 4,5 5,0
0,1
1
10
O: 2,28 nm
Ti: 2,73 nm
N: 3,0 nm
Ca: 3,58 nm
C: 4,36 nm
Ti N
Ca
H2O
C
Absorp
tion length
(µ
m)
Wavelength (nm)
Accessable absorption edges Spectrum of Krypton plasma
B, C, N, O, F, S, Ca, Ti, Mn, Fe…
Table-top NEXAFS Spectrometer
= 1 …7nm, 10 …20nm
Source sample spectrometer
200 250 300 350 400 450
0
2000
4000
6000
8000
10000
12000
14000
0,0
0,2
0,4
0,6
0,8
1,0
Inte
nsity [C
CD
-Co
un
ts]
Photonenenergy [eV]
without sample
with Polyimid (d=200nm)
Transmission Carbon (CXRO)
Tra
nsm
issio
n
280 290 300 310 3200,0
0,5
1,0
1,5
2,0
*C-N
*C=C
*C=O
*C=O
Optic
al d
ensi
ty [
a.u
.]
Photon energy [eV]
*C=C
Polyimide
C. Peth, K. Mann et al., J. Phys. D 41 (2008) 105202
Carbon
K-edge
Synchrotron
(J. Stöhr)
60 laser pulses
polyimide
sample
(d=200nm):
Laser polychromatic concept („single-shot“)
transmission of thin samples
Compact NEXAFS spectrometer
= 1 …7nm
10 …20nm
pump-probe exp.
measurement in
ambient air
NEXAFS spectroscopy on thin films
Lipid membranes (carbon K-edge)
E. Novakova, C. Peth, K. Mann, T. Salditt et al.: Biointerphases, 3 (2008) FB44
285 290 295 300 305 310 315
0
1
2
3
4
Optic
al d
ensi
ty
Photon energy (eV)
C=C*
DOPS
DOPC
DMPC
4,4 4,3 4,2 4,1 4 3,9
Wavelength [nm]
PCMO (Perovskite-type manganate)
300 400 500 600 700 800 900 10001,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
1,9
2,0
Optical T
hic
kness [a.u
.]Photon-Energy (eV)
NEXAFS-Spectrum PCMOCaL 2,3
NK
OK
MnL 2,3
PrM 4,5
: Pr, Ca
: O
: Mn
Every element visible
(single shots)
Pump-probe experiments
phase transitions
Pr1-xCaxMnO3 (S. Techert) (T. Salditt)
P. Grossmann, S. Techert, C. Jooss, K. Mann et al.: Rev. Sci. Instr. 2012
NEXAFS at Fe L2,3 edge
Example:
Prussian Blue
► Iron L2,3 edge ► Carbon K edge
• Photon energy ~ 720eV
• 300 laser pulses
Improvements (1):
Power density: ns ps laser
Xe (Z = 54)
Single pulse XUV spectra
200 400 600 800 100010
1
102
103
104
200 400 600 800 100010
1
102
103
104
200 400 600 800 1000
101
102
103
200 400 600 800 100010
2
103
104
200 400 600 800 100010
2
103
104
200 400 600 800 100010
2
103
104
Photon energy (eV)
Single-Pulse - Max. Laserpulse-Energy - Al filteredNitrogen Oxygen Neon
Photon energy (eV) Photon energy (eV)
Photon energy (eV)
Argon Krypton Xenon
Photon energy (eV) Photon energy (eV)
Single pulse XUV spectra
Single pulse XUV spectra
Single pulse spectra:
O (Z = 8) Ne (Z = 10) N (Z = 7)
Ar (Z = 18) Kr (Z = 36)
8ns
450mJ
150ps
380mJ
Peak brillance of isolated N line @ = 2.88nm:
6*1017 (ns laser) 1.2*1020 Ph./(s mrad2 mm2 0,1%BW) (ps laser)
Simulation of spectra: Ar
ns laser ps laser
electron temperature [eV]
50.3 66.3
electron density [1019 e/cm³]
7.0 22.4
Calculation with
MHD code
PrismSPECT
measured measured
simulated simulated
ps ns
M. Müller, K. Mann et al.: Opt. Express 21 (2013)
Nitrogen
10 bar
Helium
170 mbar
14
Nitrogen
10 bar
Vacuum
~10-3 mbar
500 µm 500 µm
T. Mey, M. Rein, K. Mann, New J. Phys. 14 (2012) 073045
~10x brilliance
increase
@ = 2.88 nm
Improvements (2): Plasma generation with barrel shock
Schlieren
image
ellipsoidal mirror laser
plasma
caustic measurement
Improvements (3):
Focusing optics for x-ray plasma
Nitrogen plasma, = 2.88nm (monochromatic)
grazing incidence ellipsoidal mirror
focus dia. ~ 500µm
Ablation of PMMA @ =2.88nm
FWHM
≈ 500 µm
focal spot of elliptical mirror:
~ 1 mJ/cm² @ 2.88 nm
≈ 8.5*109 photons/pulse
5000 N2 pulses @ 15 bar,
3 min ultrasonic bath
Kr plasma (3 …6nm): ~ 100mJ/cm²
ellipsoidal mirror laser
plasma
caustic measurement
Improvements (3):
Focusing optics for x-ray plasma
Nitrogen plasma, = 2.88nm (monochromatic)
grazing incidence ellipsoidal mirror
focus dia. ~ 500µm
Optics adjustment: time-consuming…
18
Wavefront measurements
Hartmann-Shack sensor:
wavefront:
Wavefront w(x,y)
= surface Poynting-Vektor S(x,y)
(ISO 15367-2)
directional
distribution
intensity
distribution
Hartmann
plate
Beam characterization of FLASH
Adjustment of beam line optics by
online wavefront monitoring = 5 .. 30nm
Experimental setup at BL2
-0.5
0.29 0.53
0.0
Pitch [mrad]
Yaw
[mrad] 0.5
0.21 0.36
wrms=13nm
wrms=15.5nm
wrms=2.6nm wrms=5.9nm wrms=2.6nm wrms=3.5nm
[1] B. Flöter et al, Beam parameters of FLASH beamline BL1 from Hartmann wavefront
measurements, Nucl. Instrum. Meth. A 635 (2011) 5108-5112
Hartmann
plate
Beam characterization of FLASH
= 5 .. 30nm
Experimental setup at BL2
wrms~ 10nm wrms~ 2.5nm ~ /10
Wavefront
Intensity
after
adjustment
before
adjustment
[2] B. Flöter et al, EUV Hartmann sensor for wavefront measurements at the Free-electron
LASer in Hamburg, New J. Phys. 12 (2010) 083015
Beam profiles and wavefronts of single pulses (no focusing mirror)
Beam propagation parameters X Y wpv [nm] 5.3 ± 0.69
wrms [nm] 0.67 ± 0.09
Beam propagation parameter M2 1.15 ± 0.08 ()
Beam propagation parameter M2i 1.23 ± 0.1 1.1 ± 0.1 ()
Beam width d [mm] 6 ± 0.2 4.4 ± 0.1
Waist position z0,i [m] -109.2 ± 0.9 -99.2 ± 1.4
Rayleigh length zR [mm] 3760 ± 484 5090 ± 731
Waist diameter d0,i [µm] 2nd moment 200 ± 20 223 ± 25 ()
Divergence [µrad] 55 ± 2 44 ± 2 ()
Beam parameters from Hartmann data
FLASH BL2 @=7nm
Beam characterization
at FERMI@Elettra / Triest @ = 32nm
Active KB System
Wavefront sensor
Focal spot size:
Computed PMMA imprint
10x10µm²
Summary:
Laser plasma EUV / soft x-ray source
Clean, stable, compact
=1…20nm, ns…ps pulses
reflectometry, ablation studies, NEXAFS / EXAFS for chemical analysis
spectro-microscopy
Hartmann wavefront sensor (EUV / soft x-rays)
real-time alignment of optics
beam propagation for single pulses
Characterization of partially coherent radiation Wigner distribution
• Dr. B. Schäfer
• Dr. U. Leinhos
• J.O. Dette
• W. Hüttner
• F. Kühl
• M. Lübbecke
• T. Mey
• M. Müller
• G. Steinert
• J. Sudradjat
• M. Stubenvoll
Thank You !
Coworkers:
XUV peak brillance
of laser plasma source
400 450 500 550 600 650 700
0
10000
20000
30000
40000
50000
60000
N VII 1s2-1s5p
N VII 1s2-1s4p
N VI 1s2-1s6p
N VI 1s2-1s5p
N VII 1s2-1s3pN VI 1s
2-1s4p
N VII 1s2-1s2p
N VI 1s2-1s2p
CC
D-C
ounts
Photonenenergie (eV)
Stickstoff - Einzelpuls - Al gefiltert
N VI 1s2-1s3p
Isolated N VI 1s2-1s2p line @ 2.8787nm (Ti filtered)
Peak brillance [Photons/(s mrad2 mm2 0,1%BW)]
ns laser: 6*1017 (LLG, T. Wilhein)
ps laser: 1,2*1020 (LLG)
Brightness (ps): ~1014 photons/(pulse x sr)
Comprehensive beam characterization Wigner distribution
= Fourier transform of Mutual Coherence Function
Intensity distribution Beam diameter
CCD camera
Phosphor coated screen
Translation stage
Long working distance
microscope
Caustic of FLASH:
Determination of
Wigner distribution function
ℎ𝑥 𝑥, 𝑢 = ℎ 𝑥, 𝑦, 𝑢, 𝑣 𝑑𝑦𝑑𝑣 ℎ𝑦 𝑦, 𝑣 = ℎ 𝑥, 𝑦, 𝑢, 𝑣 𝑑𝑥𝑑𝑢 mapping measured data into 4D Wigner Fourier space
FFT
Reconstruction
of beam profiles
▼ Wigner distribution
function
comprehensive
beam characterization
beam parameters
coherence function
mode content
wavefront
angular characteristics B. Schäfer, T. Mey, K. Mann, K. Tiedtke et al, Nucl. Inst. Meth. 2011
Spectrum of electromagnetic radiation
Wavelength
Photon energy
EUV Lithography 13.5 nm
Excimer
lasers
Soft x-rays
Hard x-rays
Free electron
lasers
„water window“
1µm 100nm 10nm 1nm 0.1nm
1eV 10eV 100eV 1keV 10keV
Extreme UV
High
Harmonics
Gepulstes Hochdruck-Gastarget
A) monochromatische Strahlung @=2,88nm (N2 + Ti-Filter)
B) Bichromatisches Konzept zur elementspezifischen
Mikroskopie um die Ca-Kante (=3,58 nm)
Spektro-Mikroskopie
Kompaktes Labor-Röntgenmikroskop
NEXAFS measurements at athmospheric pressure
2 – 4mm
Polyimide:
Nitrogen
10 bar
Helium
170 mbar
31
Nitrogen
10 bar
Vacuum
~10-3 mbar
500 µm 500 µm
Improvements (2): Plasma generation with barrel shock
Schlieren
image
Improvements (3):
Barrel shock
10-3mbar
1 bar
Nitrogen
10bar
ambient
pressure:
32
500µm
Schlieren
images:
Beam characterization:
Hartmann-Shack wavefront sensor
Zernike
Analysis:
Beam
parameters:
Propagation
analysis
- Wavefront
Spot distribution - Beam profile
33
2222 4 xx
x xxM
B.Schäfer, K. Mann, Rev. Sci. Instr. 77, 053103 (2006)
EXAFS: Cl L-edge of NaCl
► 200nm NaCl film
► L-edge of Cl (EUV range)
► Bond lengths:
Excellent agreement with
Synchrotron data
EXAFS structures
Streui
iEE
CR
Results and discussion I - Overview
17 November
2013
Emission properties of ns and ps laser-induced soft x-ray sources 35
Results and discussion III – different pulse energies
17 November
2013
Emission properties of ns and ps laser-induced soft x-ray sources 36
N2 Kr
The higher emission intensity of the ps plasma and shift to shorter wavelengths
(considering the same pulse energy of ns and ps laser) is attributed to the higher electron
density and higher electron temperature, respectively.
Results and discussion VI
37
Parameter ns laser ps laser
Wavelength (λ) 1064 nm 1064 nm
Pulse duration (τ) (FWHM) 7 ns 0.17 ns
Laser pulse energy (Q) 450 mJ 380 mJ
Diameter of focal spot 30 µm 20 µm
Maximum power density 2.2 x 1012 W/cm² 1.7 x 1014 W/cm²
Plasma size 470 µm x 190 µm 310 µm x 150 µm
Brightness 5 x 1012 photons/(pulse x sr) 8 x 1013 photons/(pulse x sr)
Peak Brilliance @ 2.88 nm 1 x 1015 photons/(s x mrad² x mm²) 4 x 1018 photons/(s x mrad² x mm²)
38
Soft x-ray microscopy II
caustic measurement
0
10 25
50
-10 -25
-50
z [mm]
FWHM
≈ 500 µm
17 November
2013
39
Soft x-ray microscopy III
Applications of ns and ps laser-induced soft x-ray sources
dose [mJ/cm² x number of pulses]
de
pth
[n
m]
EUV energy density [mJ/cm²]
ablation
fragmentation
Ablation of PMMA @ 2.88nm
energy density between 0.3 mJ/cm² -
0.5 mJ/cm² @ 2.88 nm in the focal
spot of the elliptical mirror
≈ 8.5*109 photons/pulse 5000 pulses, N2 @ 15 bar,
3 min ultrasonic bath
@ 13.5 nm
17 November
2013
40
Soft x-ray microscopy IV
Applications of ns and ps laser-induced soft x-ray sources
2.3*1012 photons/(sr*pulse ) 1.8*1011 photons/(sr*pulse )
R ≈ 8%
Caustic of HHG Source
25. Harmonic (=32nm)
x y
Waist diameter d0 91.5 µm 243.4 µm
Waist position z0 312.6 mm 402.6 mm
Rayleigh length zR 10.7 mm 30.1 mm
Beam propagation factor M² 19.7 50.0
90.0 mm
z0y
d0y
√2·d0y
zRy
Aberrations !
Real-time wavefront measurement
25. Harmonic (=32nm)
42
Yaw angle
Pitch angle !
Spatial coherence:
interference of elementary waves
𝑥 − 𝑠 /2
𝑥 + 𝑠 /2
𝑑
43
𝑠
2𝑎
Young´s experiment:
Contrast of fringes
local degree of coherence 𝛾 𝑥 , 𝑠 :
Caustic of Free Electron Laser FLASH / DESY
Beam
parameter Value
Waist position
z0x / z0y [mm] 131.1 / 132.6
Waist diameter
d0x / d0y [µm] 65.5 / 35.9
Rayleigh length
zRx / zRy [mm] 11.8 / 5.7
Beam propagation
factor M²x / M²y 21 / 13
coherence ???
z0x
d0x √2·d0x
zRx
44
angular coordinate 𝑢 =𝑢𝑣
spatial coordinate 𝑥 =
𝑥𝑦
Wigner distribution
ℎ 𝑥 , 𝑢 = 1
2𝜋
2
⋅ Γ 𝑥 , 𝑠 ⋅ 𝑒−𝑖𝑢⋅𝑠 𝑑2𝑠
Wigner distribution mutual coherence function
x
y
z v
Interpretation: radiance at position 𝑥 in direction of 𝑢
ℎ = Wm² ⋅ sr
M. J. Bastiaans, 1986, Opt. Acta 28 1215-24
h = Fourier transform of Mutual Coherence Function: