Short-history-of-laser-development

ShorthistoryoflaserdevelopmentJeffHecht525AuburnStreetAuburndale,Massachusetts02466E-mail:[e-mail]ceTheodoreMaiman’ssmallrubyrodcrossedthethresholdoflaseremission.Thebreakthroughdem-onstrationearnedheadlines,butintheearlyyearsthelaserwascalled“asolutionlookingforaproblem,”andtherewasagermoftruthinthejoke.Yearsofdevelopmentsincethenhavevastlyimprovedlaserper-formance,andtremendouslyincreasedtheirvariety,earninglasersim-portantrolesinscientificresearch,consumerproducts,telecommunica-tions,engineering,medicine,materialsworking,andahostofotherapplications.Thisarticlereviewsthehighlightsofthosedevelopmentsandputsthemintocontext,showinghowlasertechnologyhasevolvedtomeetapplicationrequirements.©2010SocietyofPhoto-OpticalInstrumentationEngineers.
DOI:10.1117/1.3483597Subjectterms:lasers;history;laserapplications.Paper100010SSRreceivedJan.5,2010;revisedmanuscriptreceivedJun.11,2010;acceptedforpublicationJun.19,2010;publishedonlineSep.1,2010.1IntroductionThelaserisoftengroupedwiththetransistorandthecom-puteraslandmarkinventionsofthemid-20thcentury.Allthreetechnologieshaddeepconceptualroots,andgrewandfloweredrapidlyintheyearsaftertheendofWorldWarII.Theybenefittedfromheavygovernmentandcorporatein-vestmentinphysicalresearch,arapidgrowthinthenum-bersofphysicistsandengineers,andalegacyofideasandequipmentfromthewaryears.Itwasaneraofwidespreadtechnologicalprogressandoptimism,temperedbyfearsthatColdWartensionscouldleadtonuclearwar.Althoughthepotentialofthethreetechnologiesseemsobvioustoday,itwasnotasclearinitially.Thetransistorwasfirstseenasacompact,solidstatereplacementforvacuumtubes;integratedcircuitswereinventedmorethanadecadelater.Programmableelectroniccomputersinitiallywerethoughtusefulonlyforscientificresearch.Foritspart,thelaserwasatitsbirthheraldedvariouslyasascience-fictiondeathray1orahigherfrequencycoherenttransmitterforatmosphericcommunications.2Incoveringtheevolutionoflaserscienceandtechnol-ogy,thisarticleconcentratesontwointeractingseriesofdevelopments,oflaserdevicesandoflaserapplications.Inevitably,thetwoprocessesinteracted.Applicationdevel-operstestedexistinglaserdevicesandgavelaserdevelop-ersfeedbackonnewfeaturesneededtomakeapplicationspractical.Asapplicationsevolved,theirlaserrequirementsalsoevolved.Forexample,therequirementsofearlyopti-calcommunicationsystemspusheddevelopmentofsemi-conductordiodelasers.Gallium-arsenidediodessufficedforlinksofseveralkilometersbetweentelephonecentraloffices,butwhenglassfiberswerefoundtotransmitbetteratlongerwavelengths,InGaAsPdiodelasersweredevel-opedforthewindowsat1310and1550nm.Inthissense,lasertechnologyevolvedinresponsetotheeconomicen-vironment,likeothertechnologies.3Lasershavehadarichandcomplexhistoryoverthehalf-centurysinceTheodoreMaimancrossedthethresholdofthelaserageonMay16,1960,atHughesResearchLaboratories.Thisshortarticlecannotcoverthathistoryinthedetailitdeserves.Itisimpossibletolistallsignificantdevelopmentsofthepast50years,ortocreditallthepeoplewhomadeimportantcontributionsduringthattime.Instead,Ihavefocusedonbroadtrendsinthetechnology,notingsomemilestonesalongtheway,andhopingthatIhavenotoverlookedtoomuch.ThetimelineintheAppen-dixlistskeyeventscoveredinthisarticlethrough2002,butisnotintendedtobecomprehensive.2BackgroundThefirstconceptualbuildingblockofthelaserwasAlbertEinstein’s1916proposalthatphotonscouldstimulateemis-sionofidenticalphotonsfromexcitedatoms.4RudolfLad-enburgreportedindirectevidenceofstimulatedemissionin1928.5However,physicistsofthetimecalledtheeffect“negativeabsorption,”andconsidereditoflittlepracticalimportancebecausetheyexpectedBoltzmannpopulationdistributionstobethenorm,withhigherenergystatesin-evitablylesspopulatedthanlowerlevels.In1940,RussianphysicistValentinA.Fabrikantsug-gestedthatstimulatedemissioninagasdischargemightamplifylightundersuitableconditions.6However,hedidnotproposearesonatoranddidnotfollowuponhispro-posalformanyyears.AfterWorldWarII,WillisLamb,Jr.,andR.C.Retherfordrealizedthatnuclearmagneticreso-nancecouldproducepopulationinversions7andEdwardM.PurcellandRobertV.Poundusedtheeffecttoobservestimulatedemissionof50-kHzradiowaves.8In1951,CharlesH.Townestookthenextconceptualstep,suggestingthatstimulatedemissionatmicrowavefre-quenciescouldoscillateinaresonantcavity,producingco-herentoutput.In1954,TownesandhisstudentJamesGordon9demonstratedthefirstmicrowavemaser,directingexcitedammoniamoleculesintoaresonantcavitywheretheyoscillatedat24Ghz.90091-3286/2010/$25.00©2010SPIEOpticalEngineering499,091002September2010OpticalEngineeringSeptember2010/Vol.499091002-1DownloadedfromSPIEDigitalLibraryon03Dec2010to219.234.81.137.TermsofUse:firstdismissedtheidea,butbythesummerof1957hehadchangedhismindandbega