Table Of ContentSpringer Theses
Recognizing Outstanding Ph.D. Research
Hanieh Fattahi
Third-Generation
Femtosecond
Technology
Springer Theses
Recognizing Outstanding Ph.D. Research
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Hanieh Fattahi
Third-Generation
Femtosecond Technology
Doctoral Thesis accepted by
the Max Planck Institute for Quantum Optics, Germany
123
Author Supervisor
Dr. Hanieh Fattahi Prof. FerencKrausz
Attosecond Physics MaxPlanckInstitute for QuantumOptics
MaxPlanckInstitute for QuantumOptics Garching
Garching Germany
Germany
ISSN 2190-5053 ISSN 2190-5061 (electronic)
SpringerTheses
ISBN978-3-319-20024-8 ISBN978-3-319-20025-5 (eBook)
DOI 10.1007/978-3-319-20025-5
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Every man is the creature of the age in which
he lives; very few are able to raise
themselves above the ideas of the times.
Voltaire
The first principle is that you must not fool
yourself, and you are the easiest person
to fool.
Richard Feynman
To Asghar
’
Supervisor s Foreword
Eversincescientistshavebeenabletocontrolandrecordburstsoflightshorterthan
theeyecansee,wehavebeendriventoinventnewwaystotakeourcapabilitiesto
thenextlevel,toallowustopeerdeeperintotheinnerworkingsofalloftheatoms
and molecules that make up the world around us. A revolution in this line of
research came with the invention of mode-locked dye lasers in the 1970s, which
couldproducepulsesshorterthan1ps,pavingthewayforthefieldoffemtosecond
science. This field underwent another transformation in the 1980s with the advent
of broadband solid-state laser media such as titanium-doped sapphire, which
boosted the peak and average powers of femtosecond sources by orders of mag-
nitude,aidedbytheapplicationofchirpedpulseamplificationtolaseramplifiersto
boosttheachievableintensitiestonewlimits,theabilitytostabilizeandcontrolthe
carrier-envelope phase of modelocked lasers, and by the use of chirped multilayer
mirrors to allow for the control of dispersion over wavelength ranges reaching an
octave.
These were the key ingredients for us to reach into a new realm of light–matter
interaction:attosecondphysics,wherethetimeresolutionofourmeasurementshas
beenabletoreachthetimescaleofelectronicmotion.However,themoreoneworks
withagiventechnology,themoreonebecomesawareofitslimitations:inthecase
of solid-state lasers, these are primarily the simultaneous availability of high peak
and average powers, combined with ultra-broadband spectra, which would be
necessary to, for example, form single-cycle bursts of extremely-intense light to
drivethenextgenerationofX-raysourcesallowingfortime-resolvedinvestigation
of the exact motion of electron density in complex molecules and solids.
So, how do we get there? To keep both high power and broad bandwidth
presents a challenge, since increasing the emission bandwidth in a laser tends to
leadtoanincreaseinthequantumdefectandsubsequentefficiencyloss.However,
we can use nonlinear optics to overcome this limitation: optical parametric
amplification (OPA) can yield both efficient energy transfer and broad gain band-
widths, while simultaneously making use of only virtual transitions in the gain
medium,leavingverylittleheatbehindinthecrystal,pavingthewayforsubstantial
ix
x Supervisor’sForeword
increases in power. This is new territory for many of us in laser physics, though:
how do we go from the understanding of the basic optical principles involved and
go about making a practical, next-generation light source?
Now, perhaps, is a good time for me to introduce Hanieh Fattahi. She came to
Germany from Iran in 2008 to pursue her interest in photonics and dreams of an
academiccareer.Afterjoiningmygroup,shequicklygainedareputationamongher
colleagues as both as a thoroughly knowledgeable expert in nonlinear light propa-
gation and optical system design, and as a patient and insightful teacher. These
qualities are, I believe, well represented in her Ph.D. thesis, “Third-Generation
Femtosecond Technology,” which introduces the reader to the basic and
not-so-basic details of building a high-energy, high-power ultrabroadband optical
waveform synthesizer, such as the one we envision at our new laboratory, the
LaboratoryforExtremePhotonics(LEX),wheresheistakingonaleadingroleasa
postdoctoral scientist.
Starting from thebasicsoftheamplificationof photons, shediscussesall ofthe
necessary ingredients for an OPA-based next-generation light source: the genera-
tion of a broadband seed, a reliable pump laser, and the amplifier itself. These are
accompanied by numerous ideas and tips on how to improve efficiency to make
gooduseofthehigh-energypumppulses.Finally,theconcludingchapterdiscusses
the design of the synthesizer under construction at LEX, which provides a full
pictureofwhatweseeasthefrontierofultrashortpulsegenerationtobeexploredin
the coming years.
I trust that beginners to the field and experts alike will find something useful in
thevastarrayofinvestigationsthatDr.FattahiperformedduringhertimeasaPh.D.
student and the detailed and accessible way in which they are described. It is an
excitingtimetobeinthefieldofultrafastandnonlinearoptics,especiallywhenone
sees the excitement and intelligence of the next generation of researchers in the
field.
Garching, Germany Prof. Ferenc Krausz
July 2015 Director
Max-Planck-Institute of Quantum Optics
Chair for Experimental Physics, Laser Physics
Ludwig-Maximilians-Universität München
Abstract
Chirped pulse amplification in solid-state lasers is currently the method of choice
for producing high-energy ultrashort pulses, having surpassed the performance of
dyelasersover20yearsago.Thethirdgenerationoffemtosecondtechnologybased
on short-pulse-pumped optical parametric chirped pulse amplification (OPCPA)
holds promise for providing few-cycle pulses with terawatt-scale peak powers and
kilowatt-scale-average powers simultaneously, heralding the next wave of atto-
second and femtosecond science.
OPCPA laser systems pumped by near-1-ps pulses support broadband and
efficient amplification of few-cycle pulses due to their unrivaled gain per unit
length.Thisisrootedinthehighthresholdfordielectricbreakdownofthenonlinear
crystals for even shorter pump pulse durations. Concomitantly, short pump pulses
simplifydispersionmanagementandimprovethetemporalcontrastoftheamplified
signal.
Thisthesiscoversthemainexperimentalandtheoreticalstepsrequiredtodesign
and operate a high-power, high-energy, few-cycle OPCPA. This includes the
generationofabroadband,high-contrast,carrierenvelopephase(CEP)-stableseed,
the practical use of a high-power thin-disk regenerative amplifier, its efficient use
for pumping a multi-stage OPCPA chain and compression of the resulting pulses.
A theoretical exploration of the concept and its extension to different modes of
operation, including widely-tunable, high-power multi-cycle pulse trains, and
ultrabroadband waveform synthesis is presented.
Finally, a conceptual design of a field synthesizer with multi-terawatt,
multi-octave light transients is discussed, which holds promise for extending the
photonenergyattainableviahighharmonicgenerationtoseveralkilo-electronvolts,
nourishing the hope for attosecond spectroscopy at hard-x-ray wavelengths.
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