Seeding with High Harmonics

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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
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Outline
I. Advantages of Seeding II. High-Harmonic
Generation III. Optimization of High-Harmonic
Generation IV. Carrier-Envelope Phase Control
V. Conclusion
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SASE properties
Time profile
Time profile (log plot)
Spectrum
GINGER simulation of SASE FEL at 0.3 nm.
For simulation speed. True bunch length will be
longer.
W.S. Graves, MIT Bates Laboratory
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Seeding for narrow linewidth
Spectrum
Output time profile
Time profile (log plot)
GINGER simulation of seeded FEL at 0.3 nm.
Same ebeam parameters as SASE case.
W.S. Graves, MIT Bates Laboratory
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Seeding for short pulse
Output time profile
Time profile (log plot)
Spectrum
GINGER simulation of seeded FEL at 0.3 nm.
Same ebeam parameters as SASE case.
W.S. Graves, MIT Bates Laboratory
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High-Harmonic Generation
Noble Gas Jet (He, Ne, Ar, Kr)
Cut-off Harmonic
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Sub-fs High-Harmonic Generation
M. Hentschel, et al., Nature, 414, 509 (2001) A.
Baltuska, et al., Nature, 421, 612 (2003)
Highest wavelength emitted depends on
carrier-envelope phase Single-Attosecond pulse
(650 as) -gt Stable seed energy is only possible
with phase controlled laser source

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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)
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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,
_at_800nm 300 nJ _at_ 30nm),
Postdeadline Paper CLEO 2002 Schnürer et al.
Few-cycle pulse 1mJ, 5 fs h
10-6,1 nJ_at_ 30nm Phys. Rev. Lett. 83, 722-725
(1999) Bartels et al. Shaped pulses Nature
406, 164 (2000) improvement by a factor
of 10 _at_ 30th harmonic H. C. Kapteyn h
10-4 - 10-5 _at_ 30th harmonic
Quasi-Phase-Matching Nature 421, 51 (2002)
improvement by a factor of 7 _at_ 30th harmonic
-gt 1 0 nJ improvement by a factor
of 100 _at_ 100th harmonic
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High Harmonic Generation in Hollow Fibers
Courtesy of M. Murnane and H. Kapteyn, JILA
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Optimization of HHG
Pulse shaping of drive laser can enhance a single
harmonic
Quasi-phase matching in 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 lt 4 nm ?
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• 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.
• Rapidly developing technology.

HHG spectra for 3 different periodicities of
modulated waveguides.
Courtesy of M. Murnane and H. Kapteyn, JILA
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Few-Cycle Pulse and HHG Generation In Photonic
Bandgap Fiber (Y. Fink, RLE_at_MIT)
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.

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Modification of Dispersion in PBG-Fibers
Matching of group and phase velocities is possible
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Phase Controlled Laser Pulses
Electric field of a 1.5-cycle optical pulse
Maximum field depends on f CE
L. Xu, et al., Opt. Lett. 21, 2008, (1996)
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Carrier-Envelope Phase and Frequency Metrology
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
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Octave, Prismless Tisapphire Laser
1mm BaF2
f 10o
Laser crystal 2mm TiAl2O3
OC 1
PUMP
L 20 cm
OC 2
BaF2 - wedges
Base Length 30cm for 82 MHz Laser
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DCM-Pairs Covering One Octave
Pump Window
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Spectra from 80 MHz and 150 MHz Laser
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Broadband, Prismless Tisapphire Laserand
Carrier-Envelope Detection
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Carrier-Envelope Beat
Frequency Comb for Optical Metrology on Ultracold
Hydrogen by Prof. Kleppner
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High-Harmonic Seed Generation (CPA)
0.5 mJ
A. Baltuska, et al., Nature, 421, 611 (2003)
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High-Harmonic Seed Generation (P-CPA)
YbYAG Amplifier 1ns, 20mJ, 1-10 kHz _at_1064 nm
Q-switched YbYAG, 1ns, 1mJ 1-10 kHz
2nd-Harmonic 1ns, 10mJ, 1-10 kHz _at_ 532 nm
5fs, 5mJ 1-10 kHz
GV-matched P-CPA with BBO
Carrier-Envelope Stabilized TiSapphire, 4 fs,
100MHz
Stret- cher
Com- pressor
Phase Control
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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
• -gt 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