Optical Resonators With Whispering-Gallery applications(7)

Theponderomotiveinteractionofanatomandphotonscon nedinaWGM,canbeusedforquantumnondemolitionmeasurements.Itwasshown[145]–[147]thatthedipoleforceexperiencedbyanatominanoff-resonantspatiallyinhomo-geneouslight eldisquantizedbythediscretenatureofthephoton.Similarschemestoperformquantumnondemolitiondetectionofopticalphotonsbyobservingthede ectionofabeamofatoms yingclosetoanopendielectricresonatorwereproposedinthestudies.

Theponderomotiveinteractionofanelectron,insteadofanatom,andphotonsinaWGM,wasproposedforaquantumnon-demolitionmeasurementofphotonnumber(thephotonnumberisde nedastheenergystoredinthemodedividedby¯hω0,whereω0isthefrequencyofthemode).Thetechniqueisbasedontheeffectofquadraticscatteringofelectronstravelingalongtheresonatorwithavelocityclosetothephasevelocityofthe

WGM谐振腔综述

ILCHENKOANDMATSKO:OPTICALRESONATORSWITHWGMs—PARTII:APPLICATIONS21

waveintheresonator[148].Themeasurementideareliesonthefactthatanelectrontravelingalongabaredielectricwaveguide(orsurfaceofaWGR),atavelocitynearthephasevelocity,ac-quiresatransversemomentumproportionaltothephotonenergyofthelightinthewaveguide.Itwasnotedthatthismomentumcanbemeasured[149].Thescatteringeffectwasanalyzedwithconsiderationforthewaveguide(andWGM)dispersion,radia-tionfriction,andthespuriousCherenkovradiation.

Aradiativecouplingofananoparticle/atomwithaWGMwasstudiedin[78],[150];seealso[130],[152]forareview.Thepossibilityofstrongcouplingbetweenaphotoncon nedinaWGMandanatomwasanalyzedin[153]–[155].TheresonantinteractionofanatomwithdipolarJ=0 J=1angular-momentumtransitionwiththequantized eldindielec-tricspheresandspheroidswasstudiedin[153].ThepossibilityoftheapplicationofamicrodiskWGRforthedetectionofasingletrappedatomwasstudiedin[156].

Ameasurementsofcavity-QEDeffectsfortheradiativecou-plingofatomsinadilutevaportotheexternalevanescent eldofaWGMwasreportedin[78].ExperimentsonthecouplingofasinglenanoemitterandWGMswerediscussedin[150],[151].AcompositesystemconsistingofaGaAsquantumwellstruc-tureplacedintheevanescent eldofafusedsilicamicrosphere,andevanescentcouplingbetweenexcitonsinthequantumwellandWGMsofthecompositesystem,wasdemonstratedin[157].AcompositesystemconsistingofCdSeZnSnanocrystalsandafused-silicamicrospherewasdemonstratedin[158].TheQ-factorsofthesystemwereoftheorderof108,providingamodelforinvestigatingcavityQEDandmicrolasersatthelevelofsinglequantumdots.

Opticalpropertiesofcon nedphotonstatesinanextremelysmallsphericalWGRswithsizesof2λ<R<10λ(dubbed“photonicdots”)resonantlyexcitedbyphotonsemittedfromsemiconductornanocrystals(thequantumdots)werestudiedin[159],[160]withparticularfocusonQEDpropertiesofWGRscontainingCdSequantumdotsandquantumrods.BothglassandpolymerWGRswerecharacterizedbyspatiallyandtemporallyresolvedmicrophotoluminescence.

III.WGRSWITHACTIVEMODES

SmallvolumesandhighQ-factorsofWGMsresultinen-hancementofnonlinearopticalprocesses.Duetothisenhance-ment,WGRbasednonlinearopticdevicespossessuniquechar-acteristics.Forexample,usageofWGMsallowstherealizationoflasersandwave-mixingdeviceswithmicroWattthresholds.NarrowlinewidthofWGMsresultinnarrowspectralcharacter-isticsofthelasers.Inthissection,wereviewresultsofrecentstudiesinthe eld.

A.Continuous-Wave(CW)WGMLasers

MiniaturelasersareamongthemostobviousapplicationsofWGRs.Thehighqualityfactoroftheresonatorsleadstothereducedthresholdofthelasing.The rstWGMlaserswerereal-izedinsolidmaterials[161]–[163].However,probablybecauseofthelackofinput-outputtechniquesforWGMs,theworkwasdiscontinuedatthatpoint.ThenextdevelopmentoftheWGM-basedlaserswasinliquidaerosolsandindividualliquiddroplets[164]–[169].Finally,duringthelastdecade,thelasersbasedonsolesolidstateWGRswererediscovered,demon-stratedexperimentally,andintensivelystudied.Inthissection,wereviewrecentresultswithWGRCWlasers,leavingWGRRamanlasersforSectionIII-B.

1)LasinginCapillaries:TheWGRlasercanberealizedinacylindricalresonator.Thesimplestresonatorofthiskindisacap-illary.Thegainmediumcouldresideinsidethecapillary,whereWGMsarelocalized.Forinstance,laseremissionfromWGMsinahighlyrefractivedye-dopedsolvent owinginanormallyilluminatedsilicacapillary berwasdemonstratedin[170].ThecylindricalWGMlaserdiffersfromthesphericaldropletlaser[164]inthatithasaninternalrefractiveindexdiscontinu-ity.Thelightpenetratesintotheactivemediumiftherefractiveindexofthemediumishigherthantheoneofthecapillarymaterials;e.g.,nolaserpeaksareobservedwhentherefractiveindexofthesolventislessthanthatofsilica[170].AnexampleofmicroringlasingusingCdSenanocrystalquantumdotsincor-poratedintomicrocapillarytubeswasdemonstratedin[171].Thelasinginacapillarybasedontheevanescent eldcou-plingwiththegainmediumisalsopossible.Thelayeredmicro-cavitywasrealizedin[172],[173]by owingdye-dopedethanolthroughathinwallfusedsilicacapillarytubewhoserefractiveindexwaslargerthanthatoftheliquid.Thelasingspectrumshowedastrongmodeselection,andnearlyevensinglecon-structiveinterferencepeaks,duetotheinterferentialcouplingofWGMsattheinnerboundary.Variousmodeorders,whicharenotallowedintherayopticspicture,weremadetooscillateduetotheevanescentpropagationofWGMsattheouterboundary.Theestimatedcavityqualityfactorswerehigherthan106.Thelasingcharacteristicsofresonancemodesinathindye-dopeddielectricringcavitymadeontheinnerwallofacylindricalcapillarywerealsostudiedin[174].

百度搜索“77cn”或“免费范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，免费范文网，提供经典小说医药卫生Optical Resonators With Whispering-Gallery applications(7)在线全文阅读。