femtosecond fiber lasers and amplifiers based on the pulse propagation at normal dispersion

199 Pages·2008·5.65 MB·English

FEMTOSECOND FIBER LASERS AND AMPLIFIERS
BASED ON THE PULSE PROPAGATION AT
NORMAL DISPERSION
ADissertation
PresentedtotheFacultyoftheGraduateSchool
ofCornellUniversity
inPartialFulfillmentoftheRequirementsfortheDegreeof
DoctorofPhilosophy
by
ChinYuChong
August2008
(cid:13)c 2008ChinYuChong
ALLRIGHTSRESERVED
FEMTOSECONDFIBERLASERSANDAMPLIFIERSBASEDONTHEPULSE
PROPAGATIONATNORMALDISPERSION
ChinYuChong,Ph.D.
CornellUniversity2008
Theapplicationsofultrafastopticalpulsesexplodedinlasttwodecadesincethedis-
covery of a mode-locked Ti:sapphire laser. Ti:Sapphire lasers are great ultrafast optical
pulse sources but they are not suitable for some applications since they are are bulky,
expensive,andunreliable. Sofar,solid-statelasersincludingTi:sapphirelasersaredom-
inant as ultrafast pulse sources. However, compact, inexpensive and stable fiber lasers
recently started to replace solid-state lasers. Even though fiber lasers have many practi-
cal advantages, the performance of fiber lasers is still below that of the solid-state fiber
lasers. Among many kinds of fiber lasers, a mode-locked ytterbium (Yb)-doped fiber
lasershasbeenreceivedabroadattentionformedicalapplicationssuchasthebiomedi-
cal imaging. This thesis summarizes the effort of the Yb-doped fiber laser performance
enhancementutilizingthepulsepropagationathighnormaldispersion.
In this thesis, femtosecond Yb-doped fiber lasers without anomalous dispersion el-
ement, so called all-normal-dispersion (ANDi) fiber lasers, are demonstrated based on
unique pulse shaping mechanism of the chirped pulse spectral filtering. ANDi fiber
lasers represent a new paradigm for femtosecond pulse generation. This new type of a
laserisverypracticalbecauseitavoidsthetechnicalchallengesofprovidinganomalous
dispersion without loss at 1 µm. Useful features of the ANDi fiber lasers have been
demonstrated experimentally in terms of the pulse energy, the pulse duration, the envi-
ronmentally stability, and controllable multipulsing states. Pulse energies > 20 nJ with
>100 kW peak power and pulse durations <100 fs are experimentally demonstrated.
Theoretical studies indicate that further performance improvement is quite possible.
The ANDi fiber lasers are not only practical femtosecond lasers, but also great research
toolsforultrashortpulsepropagationphenomena. Dissipativesolitonsofcomplexcubic
quinticGinzburg-Landauequationaredemonstratedexperimentallyfromanall-normal
dispersionfiberlaser.
This thesis is not limited to the demonstration of ANDi lasers. It also covers in-
teresting pulse propagation phenomena in fiber lasers and amplifiers. The formation
of a second-order dispersion managed soliton, which is referred as an antisymmetric
dispersion managed soliton, in a fiber laser with a strong dispersion map is demon-
strated. Finally,thethesisdescribesthechirped-pulse-amplificationsystemperformance
enhancementwithpropernonlinearphaseshiftandthird-orderdispersion.
BIOGRAPHICALSKETCH
ChinYuChong(AndyChong)wasborninDeajon,Korea1970. Hewasanordinary
studentwhoneverthoughthimselfasaphysicisttobe. Theyear1988wasabigyearfor
him. HeandhisfamilyimmigratedtoasmalltowninIndiana,U.S.inthatyear. Within
severalyearsofhisimmigration,hetookseveralphysicsclassesinahighschool. Those
several high school physics classes were the starting point of his long and somewhat
wildjourneytobeaphysicist.
Realizinghisundeniableinterestinphysics,hedecidedtostudyphysicsasamajorin
acollege. In1995∼96,HereceivedB.S.degreesinMechanicalengineeringandphysics
at University of Texas at Austin. After receiving B.S. degrees, he widely deviated from
the course of pursuing higher education in physics. The initial idea was to get ‘some’
experiencebeforepursuingfurthereducation. However,heworkedforseveralindustrial
companies for much longer than his initial anticipation. During his career in industry,
he always thought of pursuing Ph.D. but his courage was not enough to overcome the
momentum of a routine but a stable life-style of an industrial worker. It is certainly
true that shifting a strong momentum requires a quite a bit of an impact. A disastrous
telecom crash at late 90’s made him look into what he really wanted to do seriously.
After many years of service in the industry, he finally decided to pursue his Ph.D. at
CornellUniversity.
He joined Frank Wise group as a Ph.D. candidate in 2004. Since then, he has been
researching nonlinear optics and ultrafast pulse propagation phenomena, especially in
fiber lasers and amplifiers. During the course of the Ph.D. program, he enjoyed every
single day of learning fascinating science. Now, his journey finally has reached the
Ph.D.degreeanditwillcontinue.
Chin Yu Chong published all the journal publications under the pen name of ‘Andy
Chong’ which will be his official name after he obtains a U.S. citizenship. Currently,
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the citizenship process is delayed but eventually he will be a U.S. citizen with Andy as
hisfirstname.
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Tomyfamily,Rachel,HenryandMichelle.
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ACKNOWLEDGEMENTS
First of all, I thank to my advisor, Professor Frank Wise who has been a such a
superb advisor. The depth of his insight in science has been always amazing. At the
same time, his patience and encouragement have been invaluable in my research. I also
like to thank my committee members, Professor Chris Xu and Professor Michal Lipson
fortheirguidance.
It was such a pleasure to work with Wise group members. Among many group
members,Isincerelythankmembersofthefiberteamincluding,JoelBuckley,Hyungsik
Lim, Lyuba Kuznetsova, Shian Zhou, Will Renninger, Khanh Kieu, and Hui Liu. I am
veryproudwhatwehaveaccomplishedasateam.
Finally, I am indebted forever to my wife Michelle for her love and patient support
foralltheseyears.
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TABLEOFCONTENTS
BiographicalSketch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
TableofContents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
ListofTables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
ListofFigures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
1 Introduction 1
1.1 Organizationofthethesis . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Passivepulsepropagationinafiber . . . . . . . . . . . . . . . . . . . . 6
1.2.1 NonlinearSchro¨dingerequationandsolitons . . . . . . . . . . 6
1.2.2 Dispersion-managedsolitons . . . . . . . . . . . . . . . . . . . 9
1.2.3 Self-similarpulsepropagationandsimilariton . . . . . . . . . . 12
1.3 Pulseshapinginfiberlasers . . . . . . . . . . . . . . . . . . . . . . . . 14
1.4 Ginzburg-Landauequationanddissipativesolitons . . . . . . . . . . . 18
1.5 Fiberlasercomponentsforamplitudemodulation . . . . . . . . . . . . 20
1.5.1 Saturableabsorber . . . . . . . . . . . . . . . . . . . . . . . . 21
1.5.2 Spectralfilter . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Bibliography 31
2 All-normal-dispersion(ANDi)fiberlasers 33
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.2 Designrationaleandnumericalsimulations . . . . . . . . . . . . . . . 36
2.3 Experimentalresults . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.1 Interferencefilter . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.2 Birefringencefilter . . . . . . . . . . . . . . . . . . . . . . . . 42
2.3.3 Birefringencefiberloopfilter . . . . . . . . . . . . . . . . . . . 45
2.3.4 Er-dopedANDifiberlaser . . . . . . . . . . . . . . . . . . . . 47
2.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Bibliography 50
3 BehaviorofANDifiberlasers 52
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2 BehaviorofANDiFiberLasers: Theory . . . . . . . . . . . . . . . . . 56
3.2.1 Pulse-ShapingMechanism . . . . . . . . . . . . . . . . . . . . 56
3.2.2 VariationofLaserParameters . . . . . . . . . . . . . . . . . . 59
3.2.3 SummaryoftheEffectsofLaserParameters . . . . . . . . . . 65
3.2.4 DesignofANDilasers . . . . . . . . . . . . . . . . . . . . . . 67
3.3 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
3.5 AnalytictheoryofANDifiberlasers . . . . . . . . . . . . . . . . . . . 75
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3.6 UsefulFeaturesofANDiFiberLasers . . . . . . . . . . . . . . . . . . 78
3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Bibliography 82
4 GeneratinghighpulseenergyfromANDifiberlasers 84
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2 Numericalsimulationsandexperimentalresults . . . . . . . . . . . . . 86
4.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Bibliography 93
5 PulsedurationlimitationofANDifiberlasers 94
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.2 Numericalsimulationandexperimentalresults . . . . . . . . . . . . . 95
5.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Bibliography 102
6 EnvironmentallystableANDifiberlasers 103
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.2 Numericalsimulationsandexperimentalresultsforasigmacavity . . . 106
6.3 Numericalsimulationsandexperimentalresultsforalinearcavity . . . 111
6.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Bibliography 117
7 ControllingmultipulsingstatesinANDifiberlaserwithspectralfiltering 118
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
7.2 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
7.3 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.3.1 Converting from a high harmonically mode-locked state to a
solitonbunch . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.3.2 Quantizationofthepulseseparation . . . . . . . . . . . . . . . 124
7.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Bibliography 128
8 Antisymmetricdispersion-managedsolitoninfiberlasers 129
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
8.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
8.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Bibliography 137
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