Transcript Masciovecchio

Free Electron Laser based Multicolor Spectroscopy
C. Masciovecchio
Elettra - Sincrotrone Trieste, Basovizza, Trieste I-34149
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Introduction to FERMI Free Electron Laser
The Experimental End-Stations
EIS program (TIMEX & TIMER)
MULTICOLOR Spectroscopy
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Why Free Electron Lasers ?
1A
10keV
Peak brilliance = photons/s/mrad2/mm2/0.1%bandwidth
Synchrotron radiation
HPE FELs
1keV
1 nm
100eV
10nm
Plasma lasers
HHG in gases
LPE FELs
10eV
100 nm
1eV
1μm
Conventional lasers
1ns 100ps 10ps 1ps 100fs 10fs 1fs
Pulse Duration
Imaging with high Spatial Resolution (~ l): fixed target imaging, particle injection imaging,..
Dynamics: four wave mixing (nanoscale), warm dense matter, extreme condition, ....
Resonant Experiments: XANES (tunability), XMCD (polarization), chemical mapping, ……
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SASE vs Seeded
Electron bunch
x 105
time
Optical pulse
L. H. Yu et al., PRL (2003)
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Dt < 100 fs
Flux ~ 1013 ph/pulse
E ~ 10 - 500 eV
Total Control on
Pulse Energy
Time Shape
Polarization
E. Allaria et al., Nat. Phot. (2012); Nat. Phot. (2013)
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The Experimental Hall
EIS (Elastic & Inelastic Scattering)
C. Masciovecchio et al., J. Synch. Rad. (2015)
TIMER
TIMEX
LDM (Low Density Matter)
DIPROI (DIffraction & PROjection Imaging)
F. Capotondi et al., J. Synch. Rad. (2015)
MagneDYN (Magnetic Dynamics)
TeraFERMI (THz beramline)
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The Experimental Hall
TIMEX
DIPROI
LDM
TIMER
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DIPROI Highlights
Ultrafast Magnetic Dynamics
Controlling ultrafast demagnetization using localized optical excitation
C. von Korff Schmising, S. Eisebitt et al, submitted
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Co/Pt ML
DIPROI Highlights
A. Martin et al. (2014)
X-ray holography with customizable reference
Ideal FTH  overcoming restriction due to the reference wave  single-shot imaging
Conjugate-gradient algorithm to recover the image
FTH with an almost unrestricted choice for the reference
Known
reference
Diffraction
Sample
Longitudinal
coherence
matters!!
Hologram refined
with RAAR phase
retrivial
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Pump & Probe
The pump pulse produces a change in the sample
-
Signal
stimulate a chemical reaction
non-equilibrium states
extreme thermodynamic conditions
ultrafast demagnetization
coherent excitations
..................
that is monitored by the probe pulse
0.03
GaAs
0.02
0.01
Jitter ~ 5 fs
D R/R
WORLD RECORD !!
0
-0.01
-0.02
-0.03
-0.04
-0.05
M. Danailov et al., Opt. Express (2014)
-0.06
-1
0
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1
2
3
4
Time (sec)
5
6
7
8
9
-12
x 10
Elastic and Inelastic Scattering (EIS)
The Sample Side
Short pulses with very high peak power
What happens to the Sample?
Dt ~ 100 fs ; Peak Power ~ 5 GW ; E ~ 100 eV
Non-equilibrium distribution of electrons
Converge (electron-electron & electron-phonon collisions) to equilibrium (Fermi-like)
The intensity of the FEL pulses will determine the process to which the sample will
undergo: simple heating, structural changes, ultrafast melting or ultrafast ablation
TIMER
interior of large
planets and stars
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TIMEX
TIMEX
TIme-resolved studies of Matter under EXtreme and metastable conditions
F. Bencivenga et al., (2014)
Pump & Probe FEL
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Ti
Pump & Probe on Germanium
Pump 800 nm
Probe FEL
20 mm
Upon the absorption edge (Fermi level) the
spectroscopy is sensitive both to the Fermi
function smearing (red curve) and to the
shift of the edge due to the metallization of
the sample (blue curve)
E. Giangrisostomi et al., in preparation
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EIS - TIMER
TIMER
TIME-Resolved spectroscopy of mesoscopic dynamics in condensed matter
Challenge: Study Collective Excitations in Disordered Systems in the Unexplored w-Q region
Unsolved problems in physics
Q (q)
Determination of the Dynamic Structure Factor: S(Q,w)
10
2
10
0
10
-1
10
-2
10
-3
BL30/21
1
IUVS
BL10.2
10
INS
macro-scale nano-scale
10 -4 -3
10
-2
10
w = cs·Q
IXS
BLS
w (meV)
q
-1
10
0
10
-1
Q ( nm )
atomic-scale
1
10
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10
2
Why disordered systems at the nanoscale ?
The nature of the vibrational dynamics in glasses at the nanoscale is still unclear (V-SiO2)
M. Foret et al., PRL 77, 3831 (1996)  They are localized above ~ 1 nm-1
P. Benassi et al., PRL 77, 3835 (1996)  Existence of propagating excitations at high frequency
F. Sette et al., Science 280, 1550 (1998)  They are acoustic-like
G. Ruocco et al., PRL 83, 5583 (1999)  Change of sound attenuation mechanism at 0.1-1 nm-1
B. Ruffle´ et al., PRL 90, 095502 (2003)  Change is at 1 nm-1
C. Masciovecchio et al., PRL 97, 035501 (2006)  Change is at 0.2 nm-1
W. Schirmacher et al., PRL 98, 025501 (2007)  Model agrees with Masciovecchio et al.
B. Ruffle´ et al., PRL 100, 015501 (2008)  Shirmacher model is not correct
G. Baldi et al., PRL 104, 195501 (2010)  Change is at 1 nm-1
PRL 112, 025502 (2014); Nat. Comm. 5, 3939 (2014); PRL 112, 125502 (2014)
Fundamental to understand the low temperature anomalies in glasses
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EIS beamline - TIMER
10 2
IXS
BLS
10 1
w (meV)
10 0
Solution: Free Electron Laser based Transient
Grating Spectroscopy
IUVS
10-1
F(Q,t)
INS
10-2
Esignal
10-3
10-4
10 -3
10 -2
10 -1
-1
Q ( nm )
10 0
10 1
10 2
Q(l,q)
Epump
q
Epump
Eprobe
European Research Council
Funded Grant: 1.8 M€
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The Spectrum
Optical absorption  Temperature Grating Time-dependent Density Response
S(t)
S(t)  ( cost – F(Q,t))
Sound waves region
(driven by thermal expansion)
 region
Thermal
region
Glycerol T=205 K
H2O
2 nm-1
1600
800
0
1.6
F(Q,t) (a.u.)
S(Q,w) (a.u.)
2400
0.8
0.0
-0.8
-10
-5
0
w (meV)
5
10
Gaussian-like time profile
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1
10
t (ps)
100
Typical Infrared/Visible Set-Up
M
l1
Delay Line
DM
Probe laser beam
l2=2l1
Excitation laser beam
Phase Control (Heterodyne)
Beam stop (Homodyne)
Neutral Filter (Heterodyne)
Eex1
EL
M
DOE: Phase Mask
APD
Sample
Epr
AL1
Eex2
AL2
Es (Homodyne)
EL+Es (Heterodyne)
Challenge: Extend and modify the set-up for UV Transient Grating Experiments
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TIMER Layout
3rd harmonic (probe)
2θ
Delay line: 4 ML mirrors
(abs 1st, reflect 3rd harm),
time delays up to ~ 3 ns
θB
Beam waist
“Original beam”
Vertical
Pump1
Pump2
Horizontal
Probe
FEL pulse:1st and 3rd
harmonic (λ3 = λ 1/3)
1st harmonic (pump)
@ sample position
Vertical
Focusing
mirror
Plane Mirrors
“beam splitters”
Horizontal
R. Cucini et al et al., NIMA (2011)
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FEL Transient Grating Experiments on V-SiO2
Detector (EUV-Vis cross-corr.)
M1
FEL1
M0
0,00
DR / R
Si3N4
reference
sample
- FEL1
- FEL2
θB
Beamstops
FEL2
-0,02
-0,04
-0,06
M2
-1
0
1
2
3
Dt (ps)
λopt
ΔtFEL-FEL= ± 0.5 ps at 2θ = constant
F. Bencivenga et al., NIMA (2010)
R. Cucini et al., NIMA (2011)
R. Cucini et al., Opt. Lett. (2011)
F. Casolari et al., Appl. Phys. (2014)
M. Danailov et al. Opt. Express (2014)
R. Cucini et al., Opt. Lett. (2014)
M0
M1
2θ
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M2
FEL Transient Grating Experiments on V-SiO2
F. Bencivenga et al., Nature 2015
θ
M0
M1
kFEL,1
2θ
lFEL = 27.6 nm
2θ
θB
CCD
kFEL,2
λopt
M2
Permanent Grating after 1k-shots
Optical path difference < λFEL
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Transient Grating Experiments on V-SiO2
Hyper - Raman modes due to
coupled tetrahedral rotations
Raman modes due to
tetrahedral bending
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Acoustic-like excitations
Heterodyning with FEL
Heterodyning is a signal processing technique invented in 1901 by R. Fessenden
Time independent local field
3.0
CCD
λopt
I [arb. units]
2.5
2.0
1.5
1.0
0.5
0.0
0
20
40
60
Dt (ps)
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80
100
120
Four Wave Mixing at FEL’s
w4 k4
w1 k1
Transient grating is one of Four Wave Mixing techniques
Coherent Antistokes Raman Scattering (CARS)
S. Tanaka & S. Mukamel PRL (2002)
w3 k3
w2 k2
Charge and Energy transfer are fundamental for:
• Metal complexes
• Organic solar cells
• Metal oxides nanoparticles
• Thin heterostructures
• ………
• ………
CB
VB
ω1
ω2
Δt
ω3
ωout
atom-A
atom-B
Measure the coherence between the two different sites  it makes possible to chose
where a given excitation is created, as well as where and when it is probed
delocalization of electronic states and charge/energy transfer processes
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Multiple pulse configurations
Multiple pulses can be generated by double pulse seeding
Temporal separation between 25-300 and 700-800 fs.
Shorter separations are accessible via FEL pulse splitting.
Larger separations require the split & delay line.
Mahieu et al. Opt. Express (2013)
Spectral separation 0.4-0.7%
(E. Allaria et al., Nat. Comm 2013)
time
gain
bandwidth
spectrum
RAD2 gain
bandwidth
spectrum
MOD gain
bandwidth
time
RAD1 gain
bandwidth
spectrum
MOD gain
bandwidth
time
spectrum
Spectral separation 2-3%
or much larger if the two
radiators are tuned at
different harmonics
(Sacchi et al., in preparation)
Two (almost) temporally
superimposed pulses at
harmonic wavelengths of the
seed. They are correlated in
phase that can be controlled
with the phase shifter
(K. Prince et al., submitted)
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l2
l1pump
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Pump & Probe on Silicon
Pump FEL
Probe FEL
E. Principi et al., in preparation
P. F. McMillan et al., Nature (2005)
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LDM Highlights
Coherent control at the attosecond time scale
K. Prince et al., submitted
Interference effect among quantum states using single and multiphoton ionization
C. Chen et al., PRL (1990)
Intensity = | M1 + M2(ϕ)| = | M1|2 + |M2(ϕ)|2 + 2 Re(M1 M2(ϕ))
Use of first (62.974 eV ) and second harmonic on 2p54s resonance of Ne
Change of the phases among the two harmonics ‘invented’ by Allaria et al.,
Signal detected as function of phase on the VMI detector
Control of the phase among the two pulses!
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Conclusions
Future Research Infrastructures: Challenges and Opportunities, July 8-11, Varenna, Italy
Conclusions
T. Scopigno
K. Nelson
M. Chergui
•
•
•
•
•
•
Charge transfer dynamics in metal complexes
Charge injection and transport in metal oxides nanoparticles
Vibrational modes in Glasses
Charge Density Wave
Quasiparticle diffusion (Polarons)
Sound velocity in Graphene
G. Knopp
A. Föhlisch
G. Monaco
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Acknowledgments
L. Giannessi
P. Finetti
O. Plekan
M. Coreno
M. Danailov
M. Zangrando
M. Manfredda
A. Gessini
E. Giangrisostomi
F. Parmigiani
F. Capotondi
R. Richter
F. Bencivenga
M. Kiskinova
M. Di Fraia
C. Callegari
A. Battistoni
R. Cucini
E. Pedersoli
E. Principi
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K. Prince
R. Mincigrucci