Transcript filburt.mit.edu

Seeding with High Harmonics
Franz X. Kaertner
Department of Electrical Engineering and
Computer Science and
Research Laboratory of Electronics,
Massachusetts Institute of Technology,
Cambridge, USA
MIT Optics & Quantum Electronics Group
Outline
I. Advantages of Seeding
II. High-Harmonic Generation
III. Optimization of High-Harmonic Generation
IV. Carrier-Envelope Phase Control
V. Conclusion
MIT Optics & Quantum Electronics Group
SASE properties
Time profile
Time profile (log plot)
10
10
8
500
8
5
4
3
2
Power (kW/bin)
10
6
Power (W)
Power (GW)
7
6
10
4
10
400
300
200
2
10
100
1
0
Spectrum
0
0
10
20
30
Time (fs)
40
50
10
0
10
20
30
Time (fs)
40
50
0
0.2995
0.3
0.3005
Wavelength (nm)
0.301
GINGER simulation of SASE FEL at 0.3 nm.
Electron beam parameters
Energy
4.0 GeV
Peak current (amp) 2000 A
RMS emittance
0.8 mm
RMS energy spread .01 %
Laser beam parameters
Pulse FWHM
35 fs (~ebeam
length)
Saturation power
~3.0 GW
Energy
0.2 mJ
Charge
Beam power
Bunch FWHM
FWHM linewidth
Saturation length
80 pC
8.0 TW
40 fs
W.S. Graves, MIT Bates Laboratory
7.0E-4
59 m
For simulation speed. True bunch length will be longer.
MIT Optics & Quantum Electronics Group
Seeding for narrow linewidth
Output time profile
10
2
10
1.5
10
500
1
Power (MW/bin)
Power (W)
8
Power (GW)
Spectrum
Time profile (log plot)
6
10
4
10
0.5
2
0
0
10
20
30
40
50
10
0
10
Time (fs)
GINGER simulation of
seeded FEL at 0.3 nm.
Same ebeam parameters as SASE case.
300
200
100
10
0
400
20
30
Time (fs)
40
50
W.S. Graves, MIT Bates Laboratory
0.3
0.3005
0.301
Wavelength (nm)
Seed laser parameters
FWHM
Power
Pulse
energy
0
0.2995
50 fs
0.1 MW
5 nJ
FEL output parameters
Saturation
FWHM
Saturation power
Saturation
energy
FWHM
linewidth
Saturation length
30 fs
~2.0 GW
0.1 mJ
1.0E-5
28 m
MIT Optics & Quantum Electronics Group
Seeding for short pulse
Output time profile
Time profile (log plot)
10
2
8
1.5
10
1
0.5
1
0
24.5
1000
25
25.5
26
Time (fs)
26.5
Power (kW/bin)
1.5
10
Power (W)
Power (GW)
Power (GW)
2
6
10
4
10
27
2
10
0.5
0
10
20
30
Time (fs)
40
800
600
400
200
0
10
0
Spectrum
0
50
GINGER simulation of
seeded FEL at 0.3 nm.
Same ebeam parameters as SASE case.
W.S. Graves, MIT Bates Laboratory
10
20
30
Time (fs)
40
50
Seed laser parameters
FWHM
Power
Pulse
energy
0.5 fs
10.0 MW
5 nJ
0
0.2995
0.3
0.3005
Wavelength (nm)
0.301
FEL output parameters
Saturation
FWHM
Saturation power
Saturation
energy
FWHM
linewidth
Undulator length
0.75 fs
~2.0 GW
1.5 mJ
6.0E-4
20 m
MIT Optics & Quantum Electronics Group
High-Harmonic Generation
Noble Gas Jet (He, Ne, Ar, Kr)
100 mJ - 1 mJ
XUV @ 3 – 30 nm
@ 800 nm
h = 10-8 - 10-5
t
Propagation
Recombination
0
tb
Ionization
x
N cw 0  Wb  3.17U p (t )
Energy
-Wb
wXUV
Cut-off Harmonic:
Laser electric field
MIT Optics & Quantum Electronics Group
Sub-fs High-Harmonic Generation
M. Hentschel, et al., Nature, 414, 509 (2001)
A. Baltuska, et al., Nature, 421, 612 (2003)
Electric Field
F=0
Time
F = p/2
Highest wavelength emitted depends on carrier-envelope phase
Single-Attosecond pulse (650 as)
-> Stable seed energy is only possible with phase controlled laser source
MIT Optics & Quantum Electronics Group
Dependence of HHG on carrier-envelope
phase
•
•
•
•
•
Atomic dipole moment depends on
electric field
HHG depends on carrier-envelope phase,
particularly near cutoff
Experiment: Laser intensity .7x1015
W/cm2,
pulsewidth 5 fs, propagation of 2mm
neon,
for various carrier-envelope phases
Clear dependence of HHG near the cutoff
harmonic on CEP
Discussion with H. C. Kapteyn:
Also 20 fs driver pulses need
carrier-envelope stababilization
Ref. Brabec et al. …
A. Baltuska, et al., Nature, 421, 612 (2003)
MIT Optics & Quantum Electronics Group
Published Results:
Early pioneers:
McPherson et al., J. Opt. Soc Am B4, 595 (1987)
Ferry et al., J. Phys. B 21, 131 (1987)
New results:
Takahashi et al.: 16 mJ, 35 fs, @800nm
Postdeadline Paper CLEO 2002
Schnürer et al.: Few-cycle pulse: 1mJ, 5 fs
Phys. Rev. Lett. 83, 722-725 (1999)
300 nJ @ ~30nm),
h =10-6,1 nJ@ ~30nm
Bartels et al.: Shaped pulses: Nature 406, 164 (2000)
improvement by a factor of 10 @ 30th harmonic
H. C. Kapteyn h =10-4 - 10-5 @ 30th harmonic
Quasi-Phase-Matching: Nature 421, 51 (2002)
improvement by a factor of 7 @ 30th harmonic
-> 1 0 nJ
improvement by a factor of 100 @ 100th harmonic
MIT Optics & Quantum Electronics Group
High Harmonic Generation in Hollow Fibers
Courtesy of M. Murnane and H. Kapteyn, JILA
MIT Optics & Quantum Electronics Group
Optimization of HHG
Pulse shaping of drive laser can
Quasi-phase matching in
enhance a single harmonic
modulated hollow-core waveguide.
Courtesy of M. Murnane and H. Kapteyn, JILA
How much improvement can we get with additional phase control
for the very high harmonics in the water window < 4 nm ?
MIT Optics & Quantum Electronics Group
•HHG has produced wavelengths
from 50 nm to few nanometers,
but power is very low for
wavelengths shorter than ~10 nm.
•Best power at 30 nm.
•Improvements likely to yield 10 nJ
at 8 nm.
HHG spectra for 3 different
•Rapidly developing technology.
periodicities of modulated
waveguides.
Courtesy of M. Murnane and H. Kapteyn, JILA
MIT Optics & Quantum Electronics Group
Few-Cycle Pulse and HHG Generation
In Photonic Bandgap Fiber
(Y. Fink, RLE@MIT)
(a)
(b)
Chalcogenide
Glass
Poly-Ether
Sulfone
(PES)
Temelkuran et al., Wavelength-scalable hollow optical fibers with large photonic bandgaps …, Nature, 2002. 420: p. 1885-1886.
• Truly guided modes (assuming infinite coating thickness, strong differentiation
between different modes, large core fibers effectively in single mode
• Modal Dispersion can be engineered for optimum pulse compression and/or
phase and group velocity matching in HHG.
MIT Optics & Quantum Electronics Group
Modification of Dispersion in PBG-Fibers
Dispersion D ( ps/nm-km)
Dielectric waveguide with uniform layers
20
10
0
Dielectric waveguide
with defect
-10
1.2
-
1.4
1.6
1.8
2
2.2
Vacuum wavelength (mm)
Matching of group and phase velocities is possible
MIT Optics & Quantum Electronics Group
Phase Controlled Laser Pulses
Electric field of a 1.5-cycle optical pulse
f CE
Carrier-Envelope Phase
E-Field, a.u.
1.0
even
odd
0.5
Field
0.0
-0.5
Envelope
-1.0
-40
-20
0
Time, fs
L. Xu, et al., Opt. Lett. 21, 2008, (1996)
20
40
Maximum field
depends on f CE
MIT Optics & Quantum Electronics Group
Carrier-Envelope Phase and Frequency Metrology
Optical
Clocks
Spectrum
SHG
...
0 fCEO
... f - Df f f +Df ...
o
o o
Periodic Pulse Train with T R =
Frequency
1
Df
T. Udem, et al., PRL 82, 3568 (1999)
D. Jones, et al., Science 288, 635-639 (2000)
Provides an ultrastable modelocked pulse train!
The clock of the Facility
MIT Optics & Quantum Electronics Group
Octave, Prismless Ti:sapphire Laser
1mm BaF2
OC 1
Laser crystal:
2mm Ti:Al2O3
f  10o
L = 20 cm
PUMP
BaF2 - wedges
OC 2
Base Length = 30cm for 82 MHz Laser
MIT Optics & Quantum Electronics Group
DCM-Pairs Covering One Octave
100
0.8
80
0.6
Design
M1
M2
Average M1,M2
Measured Pair
0.4
0.2
0.0
60
40
20
Group Delay (fs)
Reflectivity
1.0000
0.9990
0.9980
0.9970
1.0
0
600
Pump
Window
800
1000
Wavelength, nm
1200
MIT Optics & Quantum Electronics Group
Spectra from 80 MHz and 150 MHz Laser
-5
1.2
-10
0.8
-15
-20
0.4
-25
-30
Spectrum [a.u.]
Spectrum [dB]
0
0.0
600
800
1000
Wavelength [nm]
1200
150 MHz
80 MHz
MIT Optics & Quantum Electronics Group
Broadband, Prismless Ti:sapphire Laser
and Carrier-Envelope Detection
20 c m
Base Length = 30cm
Silver 1mm BaF2
Mirror
PUMP
o
Laser crystal:
2mm Ti:Al 2O3
BaF2 wedges OC
- F
PMT Pol.
580nm
1mm
BBO
1160nm
MIT Optics & Quantum Electronics Group
RF Spectrum [dB]
Carrier-Envelope Beat
-40
100 kHz RBW
-60
10 kHz RBW
-80
0
20
40
60
Frequency [Hz]
80x10
6
Frequency Comb for Optical Metrology on Ultracold Hydrogen
by Prof. Kleppner
MIT Optics & Quantum Electronics Group
High-Harmonic Seed Generation (CPA)
Slow carrierenvelope phase
control loop
FemtoMeter
PC-DAC
5W-Verdi pump laser
Sub-10 fs Ti:Sapphire
seed-oscillator
Pulse selector of pulses with equal phase
1-10 kHz
repetition rate
Microstructure fiber
based
carrier-envelope
phase control
(Menlo-Systems)
Dazzler
pulse
shaper
Ti:Sapphire amplifier,
1mJ, 1-10 kHz
Femtopower-Pro
5m vaccum line
High Harmonic
Generation in jet or
hollow or PBG fiber
0.5 mJ
Hollow fiber
compressor, 5fs
(optional)
A. Baltuska, et al., Nature, 421, 611 (2003)
MIT Optics & Quantum Electronics Group
High-Harmonic Seed Generation (P-CPA)
Q-switched
Yb:YAG,
1ns, 1mJ
1-10 kHz
Yb:YAG Amplifier
1ns, 20mJ,
1-10 kHz
@1064 nm
Carrier-Envelope
Stabilized Ti:Sapphire,
4 fs, 100MHz
Stretcher
2nd-Harmonic
1ns, 10mJ,
1-10 kHz
@ 532 nm
GV-matched
ComP-CPA
pressor
with BBO
5fs,
5mJ
1-10
kHz
Phase Control
MIT Optics & Quantum Electronics Group
Conclusions
• Stable HHG needs phase controlled high energy pulses
(It has been shown to be possible)
•Optimization of HHG results already to 10-5 efficiency at 30 nm
-> 10 nJ seed energies.
• Photonic Band Gap fibers lead to novel opportunities for HHG
generation because of novel opportunities for phase and group
velocity matching
•Laser technology is rapidly developing from CPA  P-CPA
MIT Optics & Quantum Electronics Group