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Extreme Light Infrastructure Workshop – Bucharest - September, 17, 2008
Cosmin Blaga
The Dawn of Attophysics
- First Steps Towards A Tabletop Attosecond X-Ray Source -
Motivation
Single Attosecond X-Ray Pulse
Structure
< 1 nmfew keVphotons
( 1 nm ~ 1.2 keV)
Dynamics
1 atomic unit of time is 25 as
hugebandwidth
( 100 eV for 25 as)
Attosecond approaches
Single Attosecond X-Ray Pulse
•coherent or cascade stimulated Raman scattering
Kaplan, Harris, Sokolov….
•solid target interactions, non-relativistic and relativistic
Kaplan, Mourou, Naumova….
•4th generation light sources: XFELs
LCLS
•high harmonic generation from gasesFarkas, Toth, L’Huillier….
A quick HHG overview – The Three Step Model
IIThe free electron is acceleratedby the field, and may return to theatomic core
IIIThe electron recombines with the atom, emitting its energy as a photon
The electron tunnels through thedistorted Coulomb barrierI
e- in Coulomb + laser fields
Short trajectories
Longtrajectories
A quick HHG overview – Ponderomotive Forces
ponderomotive potential is everything at long wavelengths
•electron ponderomotive energy (au):Up = I/42
•displacement: = E/42
•PW/cm2 titanium sapphire laser:Up ~ 60 eV & ~ 50 au
A quick HHG overview
• intense laser-atom interaction produces a comb of odd harmonic• harmonics result from the physics of a field-driven electron
25 30 35 40 45
104
105
106
Sp
ectr
al D
ensi
ty
Wavelength (nm)
H17
H35
0.8 m2 x 1014 W/cm2
Argon
• macroscopic physics (phase-matching) is important
Harmonic cutoff: 3.2*UP + IP
A quick HHG overview
25 30 35 40 45
104
105
106
Sp
ectr
al D
ensi
ty
Wavelength (nm)
H17
H35
0.8 m2 x 1014 W/cm2
Argon
Center wavelength: 35 nm
FWHM bandwidth: 7 eV
TF limit LundMilano
Bordeaux
100 as 170 as 170 as
TF limit LundMilano
Bordeaux
100 as 170 as 170 as
Generating attoseconds – Lund Group’s Recipe
• intrinsic time-structure is dominated by the beating between the strong low-order harmonics
• select the plateau region by spectral filtering
temporal profile
short
long
harmonic spectrum
Generating attoseconds – Lund Group’s Recipe
Bellini et al. PRL (1998)
select the short trajectory by
spatial filtering
harmonic spectrum temporal profile
short
long
contributions from 2 dominant trajectories
Generating attoseconds – Lund Group’s Recipe
the first trajectory exhibits an intrinsic positive chirp
compress by dispersive filtering
Lund group PRL 94, 033001 (2005)
170 as
harmonic spectrum temporal profile
The case for wavelength scaling – an IR promise
Maximum classical harmonic energy: 3.2Up Ip , UP ~ I*λ2
The case for wavelength scaling – an IR promise
Maximum classical harmonic energy: 3.2Up Ip , UP ~ I*λ2
clampedat Isat
The case for wavelength scaling – an IR promise
Maximum classical harmonic energy: 3.2Up Ip , UP ~ I*λ2
clampedat Isat
nolimitation
The case for wavelength scaling – an IR promise
Maximum classical harmonic energy: 3.2Up Ip , UP ~ I*λ2
Atom Ar He Xe Ar He He
λnm
800 800 2000 2000 2000 3600
Max UP
eV
12 60 30 75 372 1200
HHG Cutoff
eV(nm)
55(22)
216(6)
108(11.5)
255(5)
1200(1)
3800(0.3)
clampedat Isat
nolimitation
The case for wavelength scaling – an IR promise
Maximum classical harmonic energy: 3.2Up Ip , UP ~ I*λ2
Atom Ar He Xe Ar He He
λnm
800 800 2000 2000 2000 3600
Max UP
eV
12 60 30 75 372 1200
HHG Cutoff
eV(nm)
55(22)
216(6)
108(11.5)
255(5)
1200(1)
3800(0.3)
clampedat Isat
nolimitation
The case for wavelength scaling – an IR promise
Maximum classical harmonic energy: 3.2Up Ip , UP ~ I*λ2
Atom Ar He Xe Ar He He
λnm
800 800 2000 2000 2000 3600
Max UP
eV
12 60 30 75 372 1200
HHG Cutoff
eV(nm)
55(22)
216(6)
108(11.5)
255(5)
1200(1)
3800(0.3)
clampedat Isat
nolimitation
First results at 2000 nm in Argon
30 40 50 60 700
1
har
mon
ic y
ield
(au
)
Al
filte
r tr
ansm
issi
on
energy (eV)120 140 160 180 200 220
0
1
energy (eV)
Al a
nd Z
r fil
ter
tran
smis
sion
HHG Spectrum:
- cutoff corresponds ~351th-order harmonic- for constant conditions and bandwidth; (35-50 eV), I2 I0.8/1000- varying density alone; I2 I0.8/20
OPCPA for Helium HHG at 2000 nm
10Hz SECTION
STRETCHER
1kHz SECTION
Nd:YAG Diode Pumped Power Amplifier
TIME-BANDWIDTH
80MHz130ps
6nJ1064nm
1kHz130ps
1mJ 1064nm
FFS-TOPTICA
80MHz120fs
3nJ 1550nm
80MHz40fs
80pJ 2000nm
Nd:YAGOscillat
PD
STRETCHER COMPRESSOR
1kHz50fs
4mJ 2000nm
10Hz2ns
2J1064nm
80MHz100ps50pJ
2000nm
PD
FIBERLASER“FFS”
VDCCGFCC
Nd:YAGRegen
Amplifier“JAGUAR”
FR QR
BEAMshapingmodule
Nd:YAGCW-pump
HEAD
Nd:YAGCW-pump
HEAD
BD20mJ
1064nm
BD
BBO BBO
2.2 deg
Type I
BBO
2.2 degType I
BBO
Clock Synchronizer“CLX-1100”
VACUUM COMPRESSOR
10Hz100ps6mJ 2000nm
1kHz100ps6mJ 2000nm10Hz
Pulsepicker
10Hz0.5ns0.5J2000nm
10Hz60fs
0.3J2000nm
Low rep. rateNd:YAG Q-switched Laser
With Flash-Lamp Pump
2.2 degType I2.2 deg
Type I
10Hz500ps
NEAR-IR opt. pulseNd:YAG opt. pulseElectronic sync. p.
The DiMauro - Agostini Group
post-docsGilles DoumyFabrice CatoireIlya LachkoAnthony DiChiara
graduate studentsPhil Colosimo (2007)Anne Marie March Cosmin Blaga Jonathan WheelerRazvan ChirlaEmily SistrunkChristoph Roedig
collaborators: H. Muller, T. Auguste, P. Salieres, G. Paulus, K. Kulander, C. Hauri