Characterization and optimization of high-order harmonics after adaptive pulse shaping [Elektronische Ressource] / vorgelegt von Jan Lohbreier

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• Physik

Informations

• Publié par: julius-maximilians-universitat_wurzburg
• Publié le: 01 janvier 2009
• Nombre de lectures: 18
• Langue: English
• Poids de l'ouvrage: 10 Mo

Extrait

Characterization and Optimization
of High-order Harmonics after
Adaptive Pulse Shaping
Dissertation zur Erlangung des
naturwissenschaftlichen Doktorgrades
der Julius-Maximilians-Universit¨at Wu¨rzburg
vorgelegt von
Jan Lohbreier
aus Wuppertal
Wu¨rzburg 2008Eingereicht am 6. Juni 2008
bei der Fakult¨at fu¨r Physik und Astronomie
Gutachter der Dissertation:
1. Gutachter: Prof. Dr. C. Spielmann
2. Gutachter: Prof. Dr. J. Geurts
Pru¨fer im Promotionskolloquium:
1. Pru¨fer: Prof. Dr. C. Spielmann
2. Pru¨fer: Prof. Dr. J. Geurts
3. Pru¨fer: Prof. Dr. C. Honerkamp
Tag der mu¨ndlichen Pru¨fung (Promotionskolloquium): 18. Juli 2008
Doktorurkunde ausgeh¨andigt am:List of publications
Journal articles
C.Winterfeldt, J.Lohbreier, A.Paulus, T.Pfeifer, R.Spitzenpfeil, D.Walter, G.Gerber, and
C.Spielmann
Adaptive spatial control of high-harmonic generation
in Ultrafast Phenomena XV, (eds. R.J.D. Miller, A.M. Weiner, P.Corkum, D.Jonas)
(Springer, Berlin, 2006), Springer Series in Chemical Physics
D.Walter, S.Eyring, J.Lohbreier, R.Spitzenpfeil, and C.Spielmann
Spatial Optimization of Filaments
Appl. Phys. B88, 2, (2007)
D.Walter, S.Eyring, J.Lohbreier, R.Spitzenpfeil, and C.Spielmann
Two-dimensional evolutionary algorithm designed for high resolutions
(in preparation)
J.Lohbreier, S.Eyring, R.Spitzenpfeil, C.Kern, M.Weger, and C.Spielmann
Maximizing the brilliance of high-order harmonics in a gas jet
(submitted)
Conference contributions
J.Lohbreier, S. Formica, N.Mail, and C.MacDonald
Diffraction and Fluorescence Measurements with Polycapillary X-ray Optics
DPG-Spring Conference, Berlin, Germany, (2005)
J.Lohbreier,S.Eyring,A.Paulus,R.Spitzenpfeil,D.Walter,C.Winterfeldt,andC.Spielmann
High-order harmonics from shaped 10-fs laser pulses
Super-Intense Laser-Atom Interaction (SILAP) Conference, Salamanca, Spain (2006)
J.Lohbreier, S.Eyring, R.Spitzenpfeil, D.Walter, M.Weger, and C.Spielmann
Optimization of high-order harmonics by spatial shaping before the filament
DPG-Spring Conference, Duesseldorf, Germany, (2007)
J.Lohbreier, S.Eyring, R.Spitzenpfeil, and C.Spielmann
Adaptive Shaping of High-order harmonics
Atto 07, International Conference on Attosecond Physics, Dresden, Germany (2007)
iiiiv
J.Lohbreier, S.Eyring, R.Spitzenpfeil, and C.Spielmann
Optimization and Characterization of high-order harmonics by spatial shaping before the
filament
Meeting of the SPP 1345, Munich, Germany, (2007)
J.Lohbreier, S.Eyring, C.Kern, R.Spitzenpfeil, D.Walter, and C.Spielmann
Specially parameterized evolutionary algorithm for spatial optimization
DPG-Spring Conference, Darmstadt, Germany, (2008)Contents
1 Laser Pulses and Nonlinear Optics 3
1.1 Mathematical Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Nonlinear Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.1 Self-focusing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.2 Filamentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.3 Self-phase modulation . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.2.4 Chirped Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2.5 Spatial Beam Parameters . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3 Characterization and Generation of Ultrashort Laser Pulses . . . . . . . . . 13
1.3.1 Autocorrelation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3.2 Spectral Interferometry for Direct Electric-Field Reconstruction . . . 14
1.3.3 A state-of-the-art Laser system . . . . . . . . . . . . . . . . . . . . . 17
1.3.4 Applications of Ultrashort Laser Pulses . . . . . . . . . . . . . . . . 18
1.4 Evolutionary Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2 Adaptive Pulse Optimization 23
2.1 Pulse Shaping using a Spatial Light Modulator (SLM) . . . . . . . . . . . . 24
2.2 Optimization after a gas-filled hollow-core Fiber. . . . . . . . . . . . . . . . 26
2.2.1 Temporal Shaping . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.2 Spatio-temporal Shaping. . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3 Optimization of the Filament . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3.1 Temporal Shaping . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3.2 Spatial Shaping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.4 Improvements of the Evolutionary Algorithm . . . . . . . . . . . . . . . . . 41
2.4.1 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.4.2 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3 High-order Harmonic Generation 49
3.1 Process of HHG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.1.1 Semi-classical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.1.2 Quantum-mechanical Model . . . . . . . . . . . . . . . . . . . . . . . 53
3.1.3 Attosecond Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.2 Harmonic Generation in the Laboratory . . . . . . . . . . . . . . . . . . . . 60
3.2.1 Gas-filled hollow-core Fiber . . . . . . . . . . . . . . . . . . . . . . . 60
3.2.2 Gas-filled Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.2.3 Setup of the “Beamline” . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.3 Filtering of High-order Harmonics . . . . . . . . . . . . . . . . . . . . . . . 66
vvi CONTENTS
4 Characterization and Optimization of HHG 69
4.1 Spatial Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.2 Wavefront Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.2.1 Computational Evaluation . . . . . . . . . . . . . . . . . . . . . . . . 77
4.2.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.2.3 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . 83
A Pulse Shaper 93Introduction
When looking scientifically at matter, sooner or later the question of resolution arises.
By resolution we normally think of the smallest distance at which points can be distinctly
detected. Thisis a very physical description butalso transferredto our everyday language
looking at a certain problem usually requires a specific resolution. If you want to distin-
guish the differences between cars, houses, faces and even opinions, you have to have a
’ruler’ with a scale that allows measurement and thus comparison. And every scale we
use to judge our daily problems before we tackle them has an intrinsic resolution. The
better the resolution the more defined do we see the details of a certain topic - be it real
or virtual.
Back to the physical aspects of resolution we mostly deal with temporal and spatial res-
olution. This is because we live in a three-dimensional space and have a one-dimensional
time-axis which clearly orders our life. As argued before, a high resolution is always an
advantage but a high ’resolution of cars’ does not help when it comes to buying a house.
So even better than having a high resolution in only one aspect it is more useful to look
at different topics with an equally high resolution. Switching back to physics - because
the resolution of car-buying or house-pricing is not scientific at all - it is enough to regard
spaceandtime. Withtimebeingonedimensionalandspacethreedimensionalthatresults
in a four dimensional resolution problem. And we want the highest resolution possible -
in every dimension.
The problems with the temporal and spatial resolution are for once the different units.
While one millimeter is easy to distinguish from two millimeters and one second from
two seconds, it gets a little complicated when comparing for example 2 seconds with 2
millimeters. Fortunately more than 100 years ago a fundamental relation between time
and space was given by A. Einstein - with the drawback that it only holds for light.
Since the fastest processes and measurements in the universe involve light as well this is a
restriction that one can comply with. Now using light and looking at experiments a little
closer another fundamental relation is quickly discovered: The shorter the wavelength of
light (the higher the photon energy) the better the spatial resolution. Since this does not
includeanupperlimit, itis necessary to realize that accordingto Heisenberg’s uncertainty
principle when ’measuring’ with such a high energy, the result is always a sum of the
experiment itself and the effect of the light. This means that the light interacts in a non-
predictable way with the matter and even with vacuum. Thus using the shortest possible
wavelengths comes along with a disadvantage by strongly interfering with the experiment.
Additionally, Heisenberg also pointed out another interesting fact: The more accurately
the wavelength of the light is measured, the less one can say about its temporal structure.
Translated into everyday language this implies that a light beam with only one distinct
wavelength can not be defined by beginning and end. And beginning and end is normally
measured in time. So there is a link between the resolution of space - being defined by
the wavelength - and the resolution of time - being defined by how exact we know the
12 CONTENTS
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