Laser Spectroscopy 2: Experimental Techniques

772 Pages·2015·16.71 MB·English

by  Wolfgang Demtröder (auth.)

Wolfgang Demtröder
Laser Spectroscopy 2
Experimental Techniques
5th Edition
Laser Spectroscopy 2
Wolfgang Demtröder
Laser Spectroscopy 2
Experimental Techniques
5th Edition
Prof.Dr.WolfgangDemtröder
UniversityofKaiserslautern
Kaiserslautern,Germany
ISBN978-3-662-44640-9 ISBN978-3-662-44641-6(eBook)
DOI10.1007/978-3-662-44641-6
SpringerHeidelbergNewYorkDordrechtLondon
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Preface to the Fifth Edition
The second volume of “Laser Spectroscopy” covers the different experimental
techniques, necessary for the sensitive detection of small concentrations of atoms
or molecules, for Doppler-free spectroscopy, laser-Raman-spectroscopy, double-
resonancetechniques,multi-photonspectroscopy,coherentspectroscopyandtime-
resolvedspectroscopy.Inthesefieldstheprogressofthedevelopmentofnewtech-
niquesandimprovedexperimentalequipmentisremarkable.Manynewideashave
enabled spectroscopists to tackle problems which could not be solved before. Ex-
amples are the direct measurements of absolute frequencies and phases of optical
waveswithfrequencycombs,ortimeresolutionwithintheattosecondrangebased
onhigherharmonicsofvisiblefemtosecondlasers.Thedevelopmentoffemtosec-
ondnon-collinearopticalparametricamplifiers(NOPA)hasconsiderablyimproved
time-resolvedmeasurementsoffastdynamicalprocessesinexcitedmoleculesand
hasbeenessentialfordetailedinvestigationsofimportantprocesses,suchasthevi-
sualprocessintheretinaoftheeyeorthephotosynthesisinchlorophylmolecules.
In particular, the applications of laser spectroscopy in chemistry, biology
medicineandforthesolutionoftechnicalproblemshavemaderapidprogress.This
isillustratedbyseveralexamplesinthelastchapter.
Inthisneweditionsomerecentdevelopmentsarediscussed,asforinstancethe
applicationofopticalcombstoprecisionmolecularspectroscopyanditsextension
into the far UV region, to metrology, to astronomy and as frequency normal for
the global positioning system. The progress in the controllable generation of high
harmonics with frequencies up into the X-ray region and with a time resolution
in the attosecond time scale are outlined and also new techniques of cooling and
trappingofatomsormoleculesinvariousrealizationsofopticaltrapsarepresented.
ForseveralsectionsofVol.2somebasicknowledgeofspectroscopictechniques
orinstrumentationisnecessary.Therefore,crosslinkstoVol.1aregiven,wherethe
fundamentalsoflaserspectroscopyarediscussed.
Attheendofeachchaptersomeproblemsaregiven,whichshouldhelpthestu-
dentstochecktheirunderstandingofthesubjecttreatedinthecorrespondingchap-
ter.Thesolutionsaregivenattheendofthebook.
v
vi PrefacetotheFifthEdition
The author would like to thank Dr. Th. Schneider from Springer-Verlag for his
patienceandencouragementandMrs.St.Hohenseefromle-tex,whohastakencare
of the layout and printing. The author is grateful to many people who have con-
tributed to the improvement of this new edition by pointing to errors and possible
revisionsoftheformeredition.Hethanksmanycolleaguesfortheirpermissionto
usefiguresfromtheirwork.
Hewillappreciateanyfuturecooperationofreadersforimprovingthistextbook.
Anymailwithquestionsorsuggestionsforcorrectionswillbeansweredassoonas
possible.
Kaiserslautern,Germany WolfgangDemtröder
November2014
Preface to the Fourth Edition
Nearly50yearsaftertherealizationofthefirstlaserin1960,laserspectroscopyis
stillaveryintensefieldofresearchwhichhasexpandedwithremarkableprogress
into many areas of science, medicine and technology, and has provided an ever-
increasing number of applications. The importance of laser spectroscopy and its
appreciation by many people is, for instance, proved by the fact that over the last
tenyearsthreeNobelPrizeshavebeenawardedtoninescientistsinthefieldoflaser
spectroscopyandquantumoptics.
Thispositivedevelopmentispartlybasedonnewexperimentaltechniques,such
asimprovementsofexistinglasersandtheinventionofnewlasertypes,therealiza-
tion of optical parametric oscillators and amplifiers in the femtosecond range, the
generationofattosecondpulses,therevolutioninthemeasurementsofabsoluteop-
ticalfrequenciesandphasesofopticalwavesusingtheopticalfrequencycomb,or
thedifferentmethodsdevelopedforthegenerationofBose–Einsteincondensatesof
atomsandmoleculesandthedemonstrationofatomlasersasaparticleequivalent
tophotonlasers.
These technical developments have stimulated numerous applications in chem-
istry,biology,medicine,atmosphericresearch,materialsscience,metrology,optical
communicationnetworks,andmanyotherindustrialareas.
Inordertocoveratleastsomeofthesenewdevelopments,asinglevolumewould
need too many pages. Therefore the author has decided to split the book into two
parts. The first part contains the foundations of laser spectroscopy, i.e., the basic
physicsofspectroscopy,opticalinstrumentsandtechniques.Itfurthermoreprovides
a short introduction to the physics of lasers, and discusses the role of optical res-
onatorsandtechniquesforrealizingtunablenarrowbandlasers,theworkinghorses
oflaserspectroscopy.Itgivesasurveyonthedifferenttypesoftunablelasersand
representsessentiallytheupdatedandenlargededitionofthefirstsixchaptersofthe
third edition. In order to improve its value as a textbook for students, the number
of problems has been increased and their solutions are given at the end of Vol. 1.
Thesecondvolumediscussesthedifferenttechniquesoflaserspectroscopy.Com-
pared to the third edition, it adds many new developments and tries to bring the
readeruptospeedonthepresentstateoflaserspectroscopy.
vii
viii PrefacetotheFourthEdition
The author wishes to thank all of the people who have contributed to this new
edition. There is Dr. Th. Schneider at Springer-Verlag, who has always supported
theauthorandhasshownpatiencewhendeadlineswerenotkept.ClaudiaRaufrom
LE-TeXhastakencareofthelayout,andmanycolleagueshavegiventheirpermis-
siontousefiguresfromtheirresearch.Severalreadershavesentmetheircomments
onerrorsorpossibleimprovements.Ithankthemverymuch.
The author hopes that this new edition will find a similar friendly approval to
theformereditionsandthatitwillenhanceinterestinthefascinatingfieldoflaser
spectroscopy.Hewouldappreciateanysuggestionsforimprovementorhintsabout
possibleerrors,andhewilltrytoanswereveryquestionassoonaspossible.
Kaiserslautern,Germany WolfgangDemtröder
February2008
Preface to the Third Edition
LaserSpectroscopycontinuestodevelopandexpandrapidly.Manynewideasand
recent realizations of new techniques based on old ideas have contributed to the
progress in this field since the last edition of this textbook appeared. In order to
keepupwiththesedevelopmentsitwasthereforenecessarytoincludeatleastsome
ofthesenewtechniquesinthethirdedition.
Thereare,firstly,theimprovementoffrequency-doublingtechniquesinexternal
cavities, the realization of more reliable cw-parametric oscillators with large out-
put power, and the development of tunable narrow-band UV sources, which have
expanded the possible applications of coherent light sources in molecular spec-
troscopy.Furthermore,newsensitivedetectiontechniquesfortheanalysisofsmall
molecularconcentrationsorforthemeasurementofweaktransitions,suchasover-
tone transitions in molecules, could be realized. Examples are Cavity Ringdown
Spectroscopy, which allows the measurement of absolute absorption coefficients
withgreatsensitivityorspecificmodulationtechniquesthatpushtheminimumde-
tectableabsorptioncoefficientdownto10−14cm−1!
Themostimpressiveprogresshasbeenachievedinthedevelopmentoftunable
femtosecond and subfemtosecond lasers, which can be amplified to achieve suffi-
cientlyhighoutputpowersforthegenerationofhighharmonicswithwavelengths
down into the X-ray region and with pulsewidths in the attosecond range. Con-
trolledpulseshapingbyliquidcrystalarraysallowscoherentcontrolofatomicand
molecular excitations and in some favorable cases chemical reactions can already
beinfluencedandcontrolledusingtheseshapedpulses.
In the field of metrology a big step forward was the use of frequency combs
from cw mode-locked femtosecond lasers. It is now possible to directly compare
themicrowavefrequencyofthecesiumclockwithopticalfrequencies,anditturns
out that the stability and the absolute accuracy of frequency measurements in the
opticalrangeusingfrequency-stabilizedlasersgreatlysurpassesthatofthecesium
clock. Such frequency combs also allow the synchronization of two independent
femtosecondlasers.
Theincreasingresearchonlasercoolingofatomsandmoleculesandmanyexper-
imentswithBose–Einsteincondensateshavebroughtaboutsomeremarkableresults
ix
x PrefacetotheThirdEdition
andhaveconsiderablyincreasedourknowledgeabouttheinteractionoflightwith
matteronamicroscopicscaleandtheinteratomicinteractionsatverylowtempera-
tures.Alsotherealizationofcoherentmatterwaves(atomlasers)andinvestigations
of interference effects between matter waves have proved fundamental aspects of
quantummechanics.
The largest expansion of laser spectroscopy can be seen in its possible and
already realized applications to chemical and biological problems and its use in
medicine as a diagnostic tool and for therapy. Also, for the solution of technical
problems,suchassurfaceinspections,puritychecksofsamplesortheanalysisofthe
chemicalcompositionofsamples,laserspectroscopyhasofferednewtechniques.
Inspiteofthesemanynewdevelopmentstherepresentationofestablishedfunda-
mentalaspectsoflaserspectroscopyandtheexplanationofthebasictechniquesare
notchangedinthisnewedition.Thenewdevelopmentsmentionedaboveandalso
newreferenceshavebeenadded.This,unfortunately,increasesthenumberofpages.
Sincethistextbookaddressesbeginnersinthisfieldaswellasresearcherswhoare
familiarwithspecialaspectsoflaserspectroscopybutwanttohaveanoverviewon
thewholefield,theauthordidnotwanttochangetheconceptofthetextbook.
Manyreadershavecontributedtotheeliminationoferrorsintheformeredition
orhavemadesuggestionsforimprovements.Iwanttothankallofthem.Theauthor
wouldbegratefulifhereceivessuchsuggestionsalsoforthisnewedition.
Many thanks go to all colleagues who gave their permission to use figures and
resultsfromtheirresearch.IthankDr.H.BeckerandT.Wilbournforcriticalreading
ofthemanuscript,Dr.H.J.KoelschandC.-D.BachemofSpringer-Verlagfortheir
valuable assistance during the editing process, and LE-TeX Jelonek, Schmidt and
Vöcklerfor thesettingandlayout.I appreciate,thatDr.H.Lotsch,whohastaken
carefortheforegoingeditions,hassuppliedhiscomputerfilesforthisnewedition.
Last,butnotleast,IwouldliketothankmywifeHarrietwhomademanyeffortsin
ordertogivemethenecessarytimeforwritingthisnewedition.
Kaiserslautern,Germany WolfgangDemtröder
April2002