Laser a rubino

Relatedtheories

Alllight(ietraditionallightsourceorlaserlightsource)iscausedbychangesintheenergylevelsofatomsandmolecules.Theabsorptionandreleaseofthesespecificenergyleveldifferencesappearaslightofspecificwavelengths.Theenergy(Joule)emittedbythephotonisequaltoh*f,wherehisthePlanckconstantandfisthefrequencyofradiation,whichissuitableforlasersandtraditionallight-emittingsystems.Lightradiationenergyisreleasedwhenatomsfallfromahighenergystatetoalowenergystate.However,ifanatomwantstoemitlight,itmustfirstabsorbtheenergy,sothatthelow-energystateatomishittoahigh-energystate,whichiscalled"pumping"inthelaserfield.Alllightincludingspontaneousandlaserrequiresacertainamountofenergyabsorption.

Obviously,nospontaneousemissionsourcecanreachthespectralqualityofalasersource.Thisisbecausethetraditionallightsourceisamessyradiationstatethatthesystemhasatvariousenergylevels.Thebasiccharacteristicsoftraditionallightsourcesarebroadspectraldistribution,randompolarization,circularandirregularwavefrontsandlowcolortemperature.Theemissionprincipleoflaserisdifferentfromconventionallight.Itisnotcausedbyspontaneousemissionofvariousenergylevels,butstimulatedemission.Atomsofvariousenergylevelsarepumpedtoahigherexcitedstate.Thetimeisgenerallydistributednormally.Mostoftheatomsfalltothesamelowerenergystateinaveryshortperiodoftime.Thisemissionmethodcausesthelighttobeatalmostthesameenergylevel,whichiswhatweusuallycalllaser.Monochromaticity.

Inordertomaintainthenumberofflippedparticlesenough,theremustbeexternalenergytomovethefallenatomstotheexcitedstate,whichrequirespulsesinpulsedlasers(suchasYAGlasers,ruby​​lasers)Xenonlamps,semiconductorlasersindiodepumpedlasers(alsocalledDPSSlasers,suchasgreenlaserpointers),gasdischargelasers(suchashelium-neonlasers,CO2lasers),chemicallasers(suchasweapon-gradeoxygen-iodinelasers)Thechemicalreactionintheenergysourceprovidesenergy.

Manysubstancesintheworldcanbeexcitedbylight,butonlyafewsubstancescanemitusefullaserlight.Thelasersubstancemusthaveaspecificparticlestructuresothattheparticleinversiongroupcanbeexcitedtoacertaindensity,usuallysomecrystals,gases,orliquids.Theselasermaterialsaregenerallyplacedbetweentwomirrors,sothattheenergycanbeamplifiedtoausablelevelthroughmultiplereflectionsbackandforth.Amirrorisatotalmirror,whichreflectsalmostalllight,alsocalledHR,andtheotherisahalfmirror,alsocalledanoutputmirror,OC,whichgenerallyreflects20%to80%ofthelight.Thelaserisrepeatedlybetweenthetwomirrors.Afterzoomingbackandforth,apartofitistypedoutforoutput.

Shortlyafterthelaserideawasputforward,ruby​​wasfirstusedtomaketheworld'sfirstlaser.Thematrixoftheruby​​crystalforlaserisAl₂O₃,andthecrystalisdopedwithabout0.05%(weightratio)Cr₂O₃.ThedensityofCr³⁺isabout1.58×1019/cm³.Cr³⁺replacesthepositionofAl³⁺inthecrystalandisevenlydistributedinthecrystal.Optically,itbelongstoanegativeuniaxialcrystal.UndertheirradiationoftheXe(xenon)lamp,theparticlesintheruby​​crystaloriginallyinthegroundstateE1absorbthephotonsemittedbytheXelampandareexcitedtotheE3level.TheaveragelifetimeofparticlesattheE3energylevelisveryshort(about10-9seconds).MostparticlesreachtheupperenergylevelE2ofthelaserthroughnon-radiativetransitions.ThelifespanofparticlesattheE2energylevelisverylong,upto3×10^-3seconds.Therefore,alargenumberofparticlesaccumulateattheE2energylevel,formingapopulationinversionbetweenE2andE1.Atthistime,thecrystalpairfrequencyνsatisfieshν=E2—E1(wherehisPlanck'sconstant,E2andE1arelaserThephotonsoftheenergyoftheupperandlowerenergylevelshaveamplifyingeffect,thatis,thereisagaintothelightofthisfrequency.WhenthegainGislargeenoughtomeetthethresholdcondition,thereisalaseroutputwithawavelengthof6943×10^-10mattheendofthepartialreflector.

Morethanhalfoftheatomsinthe4Aenergylevel(lowenergystate)inthesystemarepumpedtoahigherenergystatebyexternalenergy,andthelasercanbereleased.ItcanbeseenfromFigure2thatmostoftheabsorptionofruby​​laserisconcentratedintworegions,T1(ultraviolet)andT2(greenlight).Thespectralwidthoftheseregionswheretheefficiencyoftheabsorptionbandisrelativelyhighisabout1000A.TheionshittotheT1/T2statequicklyfalltothe2Eenergylevel,causingthedensityofthe2Eflipgrouptoincreasetothethresholdvalueforlasershots.Belowthisthresholddensity,ruby​​canneitheremitlaserlight,norcanitbeusedtoamplifylaserlight(infact,thetwoarethesameprinciple).Afterthat,whentheenergystateisfrom2Etothelowenergystate,theextraenergyisemittedintheformoflightwithawavelengthof6943A.The6943lightemittedwhena2Eenergylevelionfallstoalowenergystatepromptsthesurrounding2Etoalsofollowit,whichcanbeunderstoodasachainreactionwitharelativelylowsuccessrate.ThispictureisanextremelysimplifiedpictureThispictureisanextremelysimplifiedandinaccuratenon-scalemodel.Itisanon-scale,inaccurateandnon-scalemodel.Itdoesnotshowsomeofthefineenergylevelsinthe2E/4Aenergylevel.Irememberthat2EChineseseemstobecalledmetastablestate.YoucanGoogleforspecificdetails.Thesefineenergylevelswillmixthe6943Alaserintosomenearbypeaks.Thisquestiondoesnotaffectgeneralexperiments.Ifyouneedaparticularlypurespectrum,youcancoolthelaserrodtoabout75K,atthistimethelinewidthwillbecomeabout10^-15GHznarrow.

Althoughtheefficiencyofruby​​laserisnothigh,only0.1%,itproducesdarkred694.3nmlight,butbecauseitsstructureisextremelysimpleandrepresentative,itisthemostwidelyusedYAGlaserstructure.Consistent,theenergylevels(three-levelsystem)aresimplerandeasiertounderstandinanalysis.Thepencoreisthickandthin,andtheruby​​rodaslongasthefingercaneasilygeneratethedetectedlaserbeamthatpenetratestheironsheetandisreflectedfromthelunarsurface.TheselasershavenotinventedthemuchmoreefficientYAGlaserrod(1%-3%),itiswidelyusedinlasercuttingmachinesanddrillingmachines,andmanymilitarynon-lethalweaponsalsousesmallerruby​​sticks.

• RubyLaserAtlas (1sheet)

• RubyLaserAtlas (1photo)

Rubyisathree-levellasermaterial.Generally,thealuminumoxidecrystalwithgoodopticalperformanceismixedwith0.03-0.4%Cr³⁺,madeintoartificialrubies,hasmuchbetteropticalpropertiesthanordinarynaturalrubies.Commonruby​​rodsrangeinsizefrom0.5cmto2cmindiameterand4cmto16cminlength.Itmaylooklikeaverylightpinkglassrodoraverydarkreddishbrown,dependingontheCrdopedconcentrationoftherod.Whenyouhititwithagreenlaserpointer,averyspecialcolorwillcomeout.

Althoughthestructureisextremelysimple,itisstillacommonhigh-energypulsedlaser.Itisasolid-statelaserequivalenttoYAGlaserandneodymiumglasslaser.Theworkingefficiencyofruby​​laserunderpulsedxenonlampirradiationisonlyabout0.1%,butduetothelongfluorescentlifetime,mechanicalQ-switching(arotatingall-reflectionprismtocompressthepulsetotheorderofnsiseasy,andthepulsepowercaneasilyexceedtrillions.watt).

HereisabriefexplanationoftheQswitch.ThesimplestQ-switchisamotorconnectedtoamirror.Whenitisnotaligned,thereisnobackandforthlight,whichcanallowthenumberofhigh-energyparticlestograduallyaccumulateandincrease.Theyarereleasedatthemomentofalignment,reachingaverynarrowandhighpower.Bigpulse.AnothertypeofQ-switchsuitableforDIYisthepassiveq-switch.Whenthelightenergydensityreachesacertainthreshold,itsuddenlychangesfromnotverytransparenttoverytransparent,causingthepreviouslygatheredhigh-energyparticlesCanbereleasedinstantly,thiskindofcrystalismoredifficulttofind,andthepriceisrelativelyhigh,youcanonlytakeluck.Theq-switchesusedintheindustryareelectro-opticQ-switching,acousto-opticQ-switching,etc.,whichareusedtofurthercompressthepulsesofpulsedlasersortomakecontinuoussemiconductor-pumpedlasercrystalsoutputpulsedlaserswithhighpeakpower,whichisconvenientMarkingandcutting.

Birthbackground

TheconceptofstimulatedemissionproposedbyEinsteinisitsimportanttheoreticalbasis.Thistheorystatesthatamaterialparticleinahigh-energystatewillbeconvertedtoalow-energystatebyaphotonwhoseenergyisequaltotheenergydifferencebetweenthetwoenergylevels,andasecondphotonwillbeproduced,whichisemittedatthesametimeasthefirstphoton.Thisisstimulatedemission.Thelightoutputbythisradiationisamplifiedandiscoherentlight,thatis,theemissiondirection,frequency,phase,andpolarizationofmultiplephotonsareexactlythesame.

Sincethen,theestablishmentanddevelopmentofquantummechanicshasenabledpeopletohaveadeeperunderstandingofthemicrostructureandmotionlawsofmatter,andtheenergyleveldistribution,transitionandphotonradiationofmicroscopicparticleshavealsobecomemorepowerful.ThisprovesthatthisalsoobjectivelyperfectsEinstein’sstimulatedemissiontheoryandfurtherlaysatheoreticalfoundationfortheproductionoflasers.Afterthebirthofquantumelectronicsinthelate1940s,itwasquicklyappliedtostudytheinteractionbetweenelectromagneticradiationandvariousmicroscopicparticlesystems,andmanycorrespondingdevicesweredeveloped.Therapiddevelopmentofthesescientifictheoriesandtechnologieshavecreatedconditionsfortheinventionoflasers.

In1951,AmericanphysicistsPurcellandPoundsucceededincausingapopulationinversioninanexperiment,andobtained50kilohertzpersecondstimulatedradiation.Later,AmericanphysicistCharlesTownsandSovietphysicistsMasovandProkhorovsuccessivelyproposeddesignsthatusetheprincipleofstimulatedemissionofatomsandmoleculestogenerateandamplifymicrowaves.

In1960,theAmericanphysicistTheodorMaymanbarelywonthisworldwidedevelopmentcompetitioninhisresearchlaboratoryinMiami,Florida.Heusedahigh-strengthflashtubetostimulatethechromiumatomsintheruby​​crystal,therebyproducingafairlyconcentratedslenderredbeamoflight,whichwhenitisshotatacertainpoint,canmakethispointreachatemperaturehigherthanthesun.

Inventor

TheAmericanphysicistandinventoroftheworld’sfirstlaser,TheodoreH.Maiman,fellillinBritishColumbia,Vancouver,Canada.Theuniversitypassedawayattheageof79.Maymansufferedfromsystemicmastocytosis,araregeneticdisease.

Throughouthislife,Maymanreceivednumerousrewards.AlthoughtheNobelPrizeinPhysicsin1964wasnotawardedtohimwhoinventedtheworld’sfirstlaser,itwasgiventotheAmericanBellLaboratoryphysicistTang,whoinventedthemaserandproposedtheprincipleanddesignofthelaser.SriLankaandtheSovietphysicistsBasovandProkhorov,butMemanwasnominatedfortheNobelPrizetwice,andwonthefamousJapanesePrizeandWolfPrizeinthefieldofphysics.Hewasalsoincludedinthe"NationalInventorsHallofFame"(NationalInventorsHallofFame)in1984.Inabookdedicatedtothe100thanniversaryofNature,TownsreferredtoMayman'spaperas"themostimportantoneofallthewonderfulpaperspublishedinthemagazineoverthepast100years."

TheeventtocommemorateMaymanisheldonMay16theachyear,whichisalsothedaywhenMayman’slasersareusedforthefirsttime.

Inventionisprocess

Thelasergeneratesakindofcoherentopticalradiation(laser)throughtheprincipleofstimulatedemissionamplification.OnJuly7,1960,the"NewYorkTimes"firstdisclosedthatMaymanhadsuccessfullymadetheworld'sfirstruby​​laser.Heirradiatedaspecialruby​​crystalthesizeofafingerwiththelightofaflashtocreateacoherentpulse.Laserbeam,thisresultlatershockedtheworld.Withtheworld'stoplaboratoriesfightingforthefirstlaserinvention,Mayman'semployeratthetime,theHughesAircraftCompanyinLosAngeles(HughesAircraftCompany)won.

However,Maymandidnotgowellwhenpublishingthearticle.Hefirstsubmittedthepapertothe"PhysicalReviewLetters"(PRL),butthetheneditorSamGoudsmitbelievedthatthiswasjustanothermaser'srepetitivework,soherefusedtopublishit.LaterMaymanfinallypublishedthearticleinthejournalNature.Ofcourse,afteryearsofhardwork,Mayman'sachievementshavebeenwidelyrecognized.

MaymanwasborninLosAngeles,CaliforniaonJuly11,1927,thesonofanelectricalengineer.Hisfatherwantedhimtobecomeadoctor,buthebelievedthatthestudyoflaserswouldhaveagreaterimpactonmedicine.AlthoughMaymanwasawildchildwhenhewasachild,hewasverygoodatmath.AftergraduatingfromtheUniversityofColoradowithamaster'sdegreein1949,MaymancametoStanfordUniversitytostudyforadoctoraldegree,andreceivedhisdoctoratein1955.HissupervisorwasWillisE.Lamb,whowontheNobelPrizeinPhysicsin1955..

WhileworkingatHughesAircraftCompany,Maymantoldhisbossthathehopedtomakealaser,butsinceotherfamouslaboratoriesdidnotproduceanyexcitingresultsatthetime,HughesstillhopedHedoessome"useful"workonthecomputer.ButMaymaninsistedonconductingresearchandthreatenedtoresign.Intheend,thecompanygavehim9months,50,000USdollarsandanassistant.

Afterthesuccessofthefirstlaser,Maymancontinuedtostudytheapplicationoflasersinmedicaltreatment,althoughthepublicatthetimebelievedthatitwasa"lethal"light.However,becauseHughesdidnotinvestmoreinthepotentialapplicationsoflasers,MaymanchosetoleaveandfoundedhisownKoradcompanyin1961.

Applicationem

Mayman’sinventionhasmadeasignificantcontributiontomankind.Lasershavebecomeindispensablebasicequipmentinmedicine,industry,andmanyscientificresearchfields.Forexample,intheapplicationofjadeprocessing,theapplicationofholographicphotos,etc.

Technologydevelopment

Obviously,theprerequisiteforlasergenerationisthatastrongbeamofultravioletandgreenlightisirradiatedintothelaserrod,sothattheionturnoverdensityreachesthethreshold.Awidelyusedmethodistouseapulsedxenonlampasastronglightsource.Thestructureisverysimple,justprojectthelightofthexenonlampontotheruby​​rod.

Hereisanintroductiontotheflash.

Flash,thereareseveralimportantparameters.Weareactuallyconcernedabouttwo,arclengthand1800v,​​theenergyofthelampundertheelectrolyticcapacitor.Ingeneral,inordertoadapttoindustrialuse,thenominalworkingvoltageofthedatasheetisavalueabove1500v.Onlybymeetingthisenergystoragevoltagecanthenominallightenergydensityandpulsewidthbeachieved(themainpeakisbelow0.5ms,whichcanmeettheneedsofpunching.).

Therearetwomainstreamflashes:

Ringflash

Theworld’sfirstlaserusedamultiRingflashlight.Theefficiencyisnotashighasthatofalinearflashlamp,buttheenergytoleranceismuchgreater.Thiskindofflashisgenerallydifficulttobuy,becausethetubelengthistoolargetotrigger,thepulseshapingnetworkisdifficulttomake,andthecapacitorenergystoragevoltageishigh,butitissuitableforaflashthatcanwithstandverylargeenergy.Thiskindofflashlightmodelingisdifficult,thedatasheetdataisverydifferent,thereisnogeneralruleofsummary.Thegeneralworkwithstandenergyexceeds2KJ.

Linearflashlamp

Today,morethan80%ofindustrialsolid-statelasersusethisxenonlampstructure.Highpumpingefficiency,convenientuseofwatercooling,simplemanufacturingprocess,andeasytriggeringarethereasonswhymostindustriallasersadoptthisstructure.Theseflashlampsarepulsedxenonlamps.Atypicalvalueisthataxenonlampwith10cmarclengthand8mmdiametercaneasilyhold2200Jofenergyunder400Venergystorage.