Theory of Nonlinear Propagation of High Harmonics Generated in a Gaseous Medium

169 Pages·2013·5.164 MB·English

by  Cheng Jin (auth.)

Springer Theses
Recognizing Outstanding Ph.D. Research
Cheng Jin
Theory of Nonlinear
Propagation of
High Harmonics
Generated in a
Gaseous Medium
Springer Theses
Recognizing Outstanding Ph.D. Research
For furthervolumes:
http://www.springer.com/series/8790
Aims and Scope
The series ‘‘Springer Theses’’ brings together a selection of the very best Ph.D.
theses from around the world and across the physical sciences. Nominated and
endorsed by two recognized specialists, each published volume has been selected
for its scientific excellence and the high impact of its contents for the pertinent
fieldofresearch.Forgreateraccessibilitytonon-specialists,thepublishedversions
includeanextendedintroduction,aswellasaforewordbythestudent’ssupervisor
explaining the special relevance of the work for the field. As a whole, the series
will provide a valuable resource both for newcomers to the research fields
described, and for other scientists seeking detailed background information on
specialquestions.Finally,itprovidesanaccrediteddocumentationofthevaluable
contributions made by today’s younger generation of scientists.
Theses are accepted into the series by invited nomination only
and must fulfill all of the following criteria
• They must be written in good English.
• ThetopicshouldfallwithintheconfinesofChemistry,Physics,EarthSciences,
Engineering andrelatedinterdisciplinaryfieldssuchasMaterials, Nanoscience,
Chemical Engineering, Complex Systems and Biophysics.
• The work reported in the thesis must represent a significant scientific advance.
• Ifthethesisincludespreviouslypublishedmaterial,permissiontoreproducethis
must be gained from the respective copyright holder.
• They must have been examined and passed during the 12 months prior to
nomination.
• Each thesis should include a foreword by the supervisor outlining the signifi-
cance of its content.
• The theses should have a clearly defined structure including an introduction
accessible to scientists not expert in that particular field.
Cheng Jin
Theory of Nonlinear
Propagation of High
Harmonics Generated
in a Gaseous Medium
Doctoral Thesis accepted by
Kansas State University, USA
123
Author Supervisor
Dr. ChengJin Prof.Chii-Dong Lin
Department of Physics Department of Physics
Kansas State University Kansas State University
Manhattan, Kansas Manhattan, Kansas
USA USA
ISSN 2190-5053 ISSN 2190-5061 (electronic)
ISBN 978-3-319-01624-5 ISBN 978-3-319-01625-2 (eBook)
DOI 10.1007/978-3-319-01625-2
SpringerChamHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2013945805
(cid:2)SpringerInternationalPublishingSwitzerland2013
Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof
the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor
informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar
methodology now known or hereafter developed. Exempted from this legal reservation are brief
excerpts in connection with reviews or scholarly analysis or material supplied specifically for the
purposeofbeingenteredandexecutedonacomputersystem,forexclusiveusebythepurchaserofthe
work. Duplication of this publication or parts thereof is permitted only under the provisions of
theCopyright Law of the Publisher’s location, in its current version, and permission for use must
always be obtained from Springer. Permissions for use may be obtained through RightsLink at the
CopyrightClearanceCenter.ViolationsareliabletoprosecutionundertherespectiveCopyrightLaw.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt
fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse.
While the advice and information in this book are believed to be true and accurate at the date of
publication,neithertheauthorsnortheeditorsnorthepublishercanacceptanylegalresponsibilityfor
anyerrorsoromissionsthatmaybemade.Thepublishermakesnowarranty,expressorimplied,with
respecttothematerialcontainedherein.
Printedonacid-freepaper
SpringerispartofSpringerScience+BusinessMedia(www.springer.com)
List of publications during Ph.D. thesis work1
[1] C. D. Lin, Cheng Jin, Anh-Thu Le, and R. R. Lucchese. Probing molecular
framephotoelectronangulardistributionsviahigh-orderharmonicgeneration
from aligned molecules. J. Phys. B 45, 194010 (2012).
[2] Guoli Wang, Cheng Jin, Anh-Thu Le, and C. D. Lin. Conditions for
extracting photoionization cross sections from laser-induced high-order-
harmonic spectra. Phys. Rev. A 86, 015401 (2012).
[3] ChengJinandC.D.Lin.Comparisonofhigh-orderharmonicgenerationof
Ar using truncated Bessel and Gaussian beams. Phys. Rev. A 85, 033423
(2012).
[4] W. Cao, G. Laurent, Cheng Jin, H. Li, Z. Wang, C. D. Lin, I. Ben-Itzhak,
andC.L.Cocke.Spectralsplittingandquantumpathstudyofhigh-harmonic
generation from a semi-infinite gas cell. J. Phys. B 45, 074013 (2012).
[5] Cheng Jin, Julien B. Bertrand, R. R. Lucchese, H. J. Wörner, Paul B.
Corkum, D. M. Villeneuve, Anh-Thu Le, and C. D. Lin. Intensity
dependence of multiple-orbital contributions and shape resonance in high-
orderharmonicgenerationofalignedN molecules.Phys.Rev.A85,013405
2
(2012).
[6] C. Trallero-Herrero, Cheng Jin, B. E. Schmidt, A. D. Shiner, J.-C. Kieffer,
P. B. Corkum, D. M. Villeneuve, C. D. Lin, F. Légaré, and A. T. Le.
Generation of broad XUV continuous high harmonic spectra and isolated
attosecond pulses with intense mid-infrared lasers. J. Phys. B (fast track
communication) 45, 011001 (2012).
[7] Guoli Wang, Cheng Jin, Anh-Thu Le, and C. D. Lin. Influence of gas
pressure on high-order-harmonic generation of Ar and Ne. Phys. Rev. A 84,
053404 (2011).
[8] Cheng Jin, Anh-Thu Le, Carlos A. Trallero-Herrero, and C. D. Lin.
Generation of isolated attosecond pulses in the far field by spatial filtering
with an intense few-cycle mid-infrared laser. Phys. Rev. A 84, 043411
(2011).
[9] Cheng Jin, Hans Jakob Wörner, V. Tosa, Anh-Thu Le, Julien B. Bertrand,
R. R. Lucchese,P. B. Corkum,D. M. Villeneuve,and C. D. Lin. Separation
of target structure and medium propagation effects in high-harmonic
generation. J. Phys. B 44, 095601 (2011).
1 Mostpartsofthisthesishavebeenpublishedin[3,5,8,9,10,12,16,18].
[10] Cheng Jin, Anh-Thu Le, and C. D. Lin. Analysis of effects of macroscopic
propagation and multiple molecular orbitals on the minimum in high-order
harmonic generation of aligned CO . Phys. Rev. A 83, 053409 (2011).
2
[11] Song-Feng Zhao, Cheng Jin, R. R. Lucchese, Anh-Thu Le, and C. D. Lin.
High-order-harmonic generation using gas-phase H O molecules. Phys.
2
Rev. A 83, 033409 (2011).
[12] ChengJin,Anh-ThuLe,andC.D.Lin.Mediumpropagationeffectsinhigh-
order harmonic generation of Ar and N . Phys. Rev. A 83, 023411 (2011).
2
[13] Song-Feng Zhao, Junliang Xu, Cheng Jin, Anh-Thu Le, and C. D. Lin.
Effect of orbital symmetry on the orientation dependence of strong field
tunneling ionization of nonlinear polyatomic molecules. J. Phys. B 44,
035601 (2011).
[14] Song-Feng Zhao, Cheng Jin, Anh-Thu Le, and C. D. Lin. Effect of an
improved molecular potential on strong-field tunneling ionization of
molecules. Phys. Rev. A 82, 035402 (2010).
[15] Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T. F. Jiang, and C. D. Lin.
Determination of structure parameters in strong-field tunneling ionization
theory of molecules. Phys. Rev. A 81, 033423 (2010).
[16] Cheng Jin, Anh-Thu Le, Song-Feng Zhao, R. R. Lucchese, and C. D. Lin.
Theoretical study of photoelectron angular distributions in single-photon
ionization of aligned N and CO . Phys. Rev. A 81, 033421 (2010).
2 2
[17] Song-Feng Zhao, Cheng Jin, Anh-Thu Le, T. F. Jiang, and C. D. Lin.
Analysisofangulardependenceofstrong-fieldtunnelingionizationforCO .
2
Phys. Rev. A 80, 051402 (2009).
[18] Cheng Jin, Anh-Thu Le, and C. D. Lin. Retrieval of target photorecombi-
nation cross sections from high-order harmonics generated ina macroscopic
medium. Phys. Rev. A 79, 053413 (2009).
[19] Van-Hoang Le, Ngoc-Ty Nguyen, C. Jin, Anh-Thu Le, and C. D. Lin.
Retrieval of interatomic separations of molecules from laser-induced high-
order harmonic spectra. J. Phys. B 41, 085603 (2008).
Supervisor’s Foreword
The interaction of light with matter is a common method for uncovering the
microscopic structure of a material in the physical world. Light sources over the
whole electromagnetic spectrum are used to ‘‘see’’ different aspects of an object.
With the invention of infrared and visible lasers since the 1960s, it has long been
possible to generate other lights in the nearby spectral range, using second har-
monics or third harmonics, via the nonlinear interaction of lasers with suitable
materials. As the laser technology advances, ultrashort high-power infrared lasers
can now be focused into an even smaller volume to create electric fields that are
comparableorgreaterthanthetypicalelectricfieldseenbyanelectroninanatom.
For more than 20 years, high-order harmonics (HH) with energies in the tens to
hundreds times of the energy of the infrared photon have been generated when
intense lasers are focused into a gas medium. These light pulses extend from the
extreme ultraviolet to soft X-rays. With suitable filters, these harmonics offer
potentiallyusefultabletoplightsourcesoverabroadspectralregion.Furthermore,
theemittedharmonicsarecoherent.Theycanalsobesynthesizedtoformisolated
attosecond pulses or attosecond pulse trains. Today these attosecond pulses are
being used to study the dynamics of atoms, molecules and condensed media, to
interrogate their evolution at the femto- and atto-second timescales.
High-order harmonics are generated by the coherent nonlinear interaction of
intense infrared lasers with atoms and molecules in the gas phase. The basic
principleforthegenerationofhighharmonicsfromeachatomormoleculeisvery
simple. Near the peak of the laser field in each half optical cycle, an electron is
ripped offfrom the atom or molecule. This electron is thrown into the oscillating
electric field of the laser and later it may be driven back to recollide with the
atomicormolecularionleftbehind.Iftheelectron,whichhasbeenacceleratedby
thelaserfield,recombineswiththeion,thentheexcessivekineticenergygainedin
the laser field is released in the form of a high-energy photon. This seemingly
simplepictureexplainstheemissionofharmonics,butformorethantwodecades
it has not been possible to carry out accurate theoretical calculations that can be
compared to harmonic spectra observed experimentally. Without a quantitative
theory,effortstoenhancetheyieldsofharmonicsinthelaboratoryhavetodepend
on experimentation alone. This has slowed down the progress of making HH for
practical applications as a useful light source.
vii
viii Supervisor’sForeword
High harmonics observed in the laboratory are generated from the coherent
emission of harmonics from all the gas atoms or molecules as the intense laser
propagates through the gas medium. In turn, the intense laser is modified by the
gas medium as it propagates. To achieve high brightness for the harmonics,
favorablephasematchingconditionsshouldbemet.Thisisachievedbyadjusting
laserfocusingconditions,gasjetposition,gaspressure,anddegreesofionization.
To account for all of these effects, it is necessary to develop a computer software
packagethatcansimulatethegeneratedharmonicspectra.Thisgoalwasachieved
by Cheng Jin, and this project forms the basis of his Ph.D. thesis.
In his thesis work, Cheng first studied harmonics generated on atomic targets.
He was able to show that the harmonic spectra of Ar atoms from the theoretical
simulation match very well with the measured ones. Later, he extended the sim-
ulations to molecular targets, for molecules that are randomly distributed or par-
tially alignedinspace.Hewasalsoabletoshowthatharmonicscan begenerated
from electrons thatare ionized from the inner orbitals ofthe molecule when laser
intensity is increased. For the first time, harmonic spectra measured in the labo-
ratory can be accurately reproduced by theoretical simulations. To make such
comparisons, interactions with experimentalists are essential since the experi-
mental conditions are required for the simulation. His work establishes a new
standard for the theoretical studies of high-order harmonic generation. It is no
longer reasonable to study harmonic generation without considering propagation
effects. After more than two decades, the details of harmonic generation in a gas
medium can finally be simulated theoretically in view of Cheng’s work.
TheimpactoftheresearchcarriedoutbyChengJinwillbefar-reachinginthe
coming years as experimentalists are pushing harmonic generation to higher
energies, with the goal of generating soft X-rays in the water window region or
even hard X-rays. For this purpose, mid-infrared long-wavelength driving lasers
(2–5microns) are beingused. Because the harmonic yields droprapidlyfor long-
wavelengthlasers,usefullightsourcesforsoftandhardX-rayscanbecomereality
and will have to depend on whether favorable phase-matching conditions with
high gas pressure can be identified, or whether one can engineer synthesized
waveform to enhance harmonics generated by individual atoms. In either endea-
vor,realisticsimulationswithmid-infraredlaserswillbeneeded.Thethesiswork
ofChengJinwillserveasagreatstartingpointforyoungresearcherstoenterthis
excitingfield,tochallengetheobstaclesthatonehastofaceinordertorealizethe
goal of using harmonic generation as an all-purpose tool for new tabletop light
sources.
Manhattan, Kansas, USA, June 2013 Prof. Chii-Dong Lin
Acknowledgments
First, I would like to sincerely thank my advisor, Dr. Chii-Dong Lin for his
guidance, encouragement, and support all through my Ph.D. study. I am really
grateful that he brings me to this exciting research field, constantly motivates me
andgivesmetheinvaluableadvice.Istillremember themostdifficulttimeinmy
project. The propagation code was working at the low gas pressure, however, it
didn’t work at the high gas pressure. I could not figure out problems for a few
months, and even wanted to give up. His patience and encouragement helped me
going through that time. I also have learned a lot from my advisor about how to
conduct the effective research and how to grab a hot topic in the field. This
valuable experience will be helpful for my future life.
IwouldliketothankDr.Anh-ThuLeforhiscontinuoushelpsinceIfirstjoined
Prof. Lin’s group. I have learned from him to run and write some computation
programmes, which soon became an essential part in my project. He is always
available for stimulated discussions, and helping me understand every concept in
the field.
Next I would like to give my appreciations to other members, former and
current,in Prof. Lin’sgroup. Dr. Rui-Hua Xie, with whom I was closely working
intheverybeginningofmyproject,taughtmestepbysteptodotheprogramming
and build up basic research tools. Dr. Turker Topcu initiated the propagation
project, and nicely shared with me his experience gathered from successful and
unsuccessful attempts. This was really useful and important for me to start a new
project.Dr.ZhangjinChenhadbeenhelpingmeinbothresearchandlifeformany
years. Dr. Toru Morishita gave me the permit to use his TDSE code, and helped
me in numerical algorithm. Dr. Song-Feng Zhao had been my collaborator in the
projectofthetunnelingionizationofmolecules,which isanimportantpartinmy
project.Hekindlyprovidedmewithnecessarydataformyproject.Andwehada
lot of good discussions in many interesting issues. I also have collaborated with
Dr. Guoli Wang inthe propagation project. I have been benefited from his efforts
to investigate propagation effects under some extreme conditions, such as high
intensity and high pressure. I appreciate my class fellow Junliang Xu, who is an
intelligentandacarefulresearcher,forhishelpandcollaborationincoursestudies.
Dr. Wei-Chun Chu and Dr. Allison Harris discussed with me about some inter-
esting problems. I really enjoyed these discussions.
ix