A pump- and probe-beam technique is used for measuring time-resolved and cw-pumped excited-state absorption (ESA) and stimulated-emission (SE) spectra of Er3+:YAlO3 with high resolution. In combination with absorption and fluorescence spectra, detailed information on the wavelengths and cross-sections of ESA and SE at the 550 nm laser transition is provided

Heumann, E.

Huber, G.

Pollnau, M.

English

Pollnau, Markus

University of Twente Research Information

OURNALOI--- LUMINESCENCEE1SEVIER Journal of Luminescence60&6l ~I994~ 542 545Stimulatedemissionandexcited-stateabsorptionat roomtemperatureon the 550 nm-lasertransition inEr3~dopedYA1O3M. Pollnau*l, E. Heumann,G. HuberImiilutc of / 00 / Phi ui /711 ci ii! of HUOI6Ui g,./uni~(usii, ii 1) 20 /Iwnhw g noun IAbstractA pump- and probe-beamtechniqueis usedfor measuringtime-resolsedandcw -pumpedexcited-stateabsorption(ESA)andstimulated-emission(SE)spectraof Eru + : YAIO with high resolution.In combinationwith absorptionandiluorescencespectra,detailedinformation on the waselengthsandcross-sections01 ESA and SF at the 55u nm lasertransition is provided.Laser action on the green Eru transition In this paper we present the measurementsof4S~—s’~I~ 2 at 550nm hasbeenachievedat low cw pumped and time-resolved ESA and SF intemperaturesin several host materials, such as Er: YAIO in the spectral region around 550 nm.BaY2F~ [I]. YAIO3 [2], and LiYF4 [3 5]. andat Owing to the high resolutionof 0.4 nm,singleStarkroom temperaturein fluorozirconatefibres [6,7]. transitionscould be resolved.In combinationwithRecently room-temperaturelasing in LiYF4 has ground-stateabsorption (GSA) and fluorescencebeen demonstrated[8]. In several of thesepapers spectra,detailed information on the wavelengthsthe possibility of parasiticESAat 550 nm from the and cross-sectionsof ESA and SE has been2 le~elhas beendiscussed.CW-pumpedESA obtained.spectraof Er~+ in silica fibres [9] suggestedthat A pump and probe-beamtechniqueis used fortheremay be an influenceof this ESA on the laser the measurementof ESA and SE spectra.Theperformanceat leastin glassesandfibres.The exact sample is excitedat 488 nm by 100 pJ pulses ofwavelengthsof lasingandESA in crystals,however, 10 nsduration from an excimer-laser-pumpedyedependon the spectral positions of single Stark laser (Coumarin 102). The Er (2.9 x 1020transitionsandon thecorrespondingcross-sections cm u): YAIO crystal(length II 9.6mm, crystalin the inxestigatedhostmaterials. lographica axis) is placedbetweentwo pinholesof200 um in diameterto definean excitationvolume.The transmittedpump light is blocked by filters.Pulsedprobelight from a broadbandXenon flashCorrespondingauthor.Presentaddress Institute of Applied Physics, Unisersits of lamp is focusedinto the sample.The transmittedBern. Sidlerstrassc5, CH-3012 Bern. Su~it,erland. probelight spectrum passes through a mono-002’ UI 94 507 Of) 1994 Elsevier ScienceB’s All righis reser~ed5.51)1 0022 2~lU9UFO28S 6M. Pollnau et al. Journalof Luminescence60&61 (1994) 842 845 843chromator (~m spectrometer with grating tel1200L1tmm, resolution 0.4nm) and is detectedbyan optical multichannelanalyzer(OMA). A pulseand delay generatorinstantaneouslytriggers the ~‘ 3Eexcimer laserand,after an adjustabledelay time,triggers the flash lamp and gates the OMA de-tector. The variation of the delay allows the 1measurementof time-resolvedESA and SE. Theset-upfor cw-pumpedESA andSE measurements 0is similar. An Ar ~ laser excites the sample at 1 Ib)488 nm. A chopperof frequency 1 Hz and duty-a 0.8cycle 1: 1 providesthe triggersignal and interruptsCthe Ar + beamfor the detectionof the unpumped 0.6probe-beamspectra. 0.4Theprobebeamhasa low intensitycomparedtothe pumpbeam,suchthat the laser-inducedpopu- 0.2lationsof the levels are unperturbed.The transmit- ~7Eted probe-beamintensity I~,after laserexcitation U 1.20and I~,without excitation as well as the cross- ~‘ i0section0GSA are measured.Theexcited-statecross- ~ o ~Lisection~ESA(~) andaSE(I) timesthe relativepopula- ~ 0.6tion factor n~/n~of the initial level i of the detected ‘~i 0.4processat wavelength A can then be calculated ~from the equation [10] ‘..U—0.2540 545 550 555 560 565 570nedln(I~/I~)+ ~GSA = ~{::aEsA(i) aSE(1)] } wavelength [nmJ(1) Fig. 1. Comparison of (a) GSA ~1~52 —.4S3 2 (resolution0.10nm),(b) fluorescence4S3 2~ 15 2 (resolution0.08nm)and(c)cw-pumpedESA ~I73~2H9 2(550 560 nm),~i ii 22G, 2and2K15 2 (560 570 nm) (resolution0.4nm) at 550 nm.Thesumin Eq. (1) extendsover all metastableandsubstantiallypopulatedlevels.Thetime-resolvedorcw excitationn~is determinedfrom thebleachingof and0.08 nm, respectively.The4S3 2 level consistsofthe GSA in the ln(I~/I~)spectrumat wavelength two Starkcomponents.With thethermallycoupledregionswhereno ESA or SE occurs.The measure-2H11 2 level taken into account,the Boltzmannment of four spectra(applicationof no beam,pump populationsof the4S312 Stark levels at 300K arebeam,probebeam,pumpandprobebeam)results b51 — 0.55 andb52 — 0.37. The ground-statemani-in a In(I~/I~)spectrum,which is free of scattered fold consists of eight Stark components,whichpumplight andspontaneousfluorescencefrom the gives 16 transitionsat 540 560 nm(Table 1). Fromsample [11]. Recently new possibilities of this the effective absorption cross-sections0abs,elf =measuringmethod havebeen demonstrated[12]. ox/doping concentration) the absolute atomicThetemporal resolutionof the ESA providesinde- cross-sectionsaarecalculatedunderconsiderationpendentinformation on the absolutepopulation of the Boltzmannpopulations.With the assump-densitiesn, of the metastablelevels as well as the tion of 5abs (line 9) — acm(line 9), the effectiveemis-effectiveexcited-statecross-sections~ESA ~ sioncross-sectionsacm eff = ab5~arecalibrated.LineThe GSA and fluorescenceshown in Figs. 1(a) 9 is chosen becauseof a high cross-sectionwithand 1(b) weremonitoredwith a resolution of 0.10 lower reabsorptionlossesthan the lines 1 and 4.544 1.1 Pollnuu i’i ul. Journal of / unilneuisni c 6O&6/ 1994j 842 84¶lable 1 1.2~bsorption and emission cro,s section, of the ~ 2 ~ delay 81.ls0.8Stark transitions.(Ao~11 afl,, ~ .,,~0.4T rarisition0— —4S Crossseciion [10 °cm2]No. / mm] 0 ~ a~,, Aa~ —0.4-0.8I I ~—~2 5408 SI 1.6 19‘ 542.~ 1 07 1 .~ (16 —1.2I i—~ I S4~.2 I S 04 1.0 06 delay 200iis2.44 2.—p I S447 S.~ 1 4 “9 1.5S ~ 6455 1.7 02 06 04 26 4—2 S47~ ~2 O~ I 10 1.67 1.—. 1 548 (1.9 0 I 0.5 0.4S S ~ 2 548 8 1.7 0.2 06 0.4 1.29 4 ~ I 549 7 1 7 0.4 “0 1.6 0.80 ~—. I 651.2 I 6 1)1 09 0.8II 6—2 SS’~6 26 0.1 09 0.8 0.4UI 7~—.2 5S42 II (1.1 0.~ 0’ 0 0I) 6—1 5549 04 0.0 02 02 714 5~2 556.7’ 00 0.4 04 ~0.4 I.1.~. • I..IS 7~I 556.7 1.616 8~l 559.2 04 00 (1.2 02 ‘U 1.2 ~~ 0.8‘UThe absolutecross-sectionsare then taken as an ~ 04averageof the valuesdeterminedfrom absorptionC\, Uand emissionspectra(Table I). All valuesof thedifference Aaeii of the effective cross-sectionsare 0.4 I535 540 545 550 555 560 555 570 575negative,which meanspopulationinversionon allwavelength [nm]Stark transitions, if an equal population of the2 and~l~ 2 levelsis achieved.Thehighestvalue Fig 2 Time-resolved ESA and SE at 550 nm, delay a) S ~is, I h)of Aaeii is calculatedfor the laserline at 549.7nm 200 ~s.and Ic) 2 ms (resolulion 0.4nm).[2]. which will be the possibletransitionfor pulsedlaseractionat room temperature,too. Its termina-ting Stark level has a Boltzmann population of a four-level laseror ESA. Populationinversionh04 0.11. at 549.7nmStimulatedemissionat room temperatureis de-tected up to 80 ps after pulsed excitation, see h5iN5n~> b0~(l n~)~ ~e > 20°c (2)Fig.2(a). A calculationof Eq. (1) consideringtheBoltzmann population (n1 n 5h5 i) leads to the requiresshort-pulseexcitationabove20°o into thefollowing result for the 549.7nm transition: with4F7 2 or2H~~2 level, which is a high requesttothe measuredquanti y(left-ha dside of Eq.(1)) at availablepumplasers.549.7nm being 1.2 x 10 20cm2(Fig. 2(a)), n5 n~ At 200 ps after pulsed excitation the relativeN5 0.68 at 8 ps delay [10], and h51 = 0.55, populationn, ne of the ~ 2 level reachesits max-a crosssectiona — 3.2 x 10 20 cm2 is determined imum and strong ESA at 560 570 nm on thefrom SE. in excellent agreementwith the value transition~2—~2G72 and2K15 2 is detected,seea 3.7 x 1020cm2 derived from GSA (Table 1). Fig. 2(b). It does not affect the fluorescence,beTherefore,this measuringmethodwill be suitable causethere is no spectral overlap.At long delayfor the precisedeterminationof cross-sectionsbe- timesthe remainingexcitation concentratesin thetweentwo excited states,e.g. the laser transition ~Il3 2 level and leads to the ESA transitionM. Pollnau et at. Journalof Luminescence60&61 (1994) 842 845 845I~32—*2H9/2 (Fig. 2(c)). This ESA influencesthe Acknowledgementslongwavelengthside of the greenfluorescenceandcounteractsSEevenat short delaytimes(Fig. 2(a)). We wish to thank H. Stangeand T. DangerofThe short wavelength end of this ESA lies only the Institute of Laser-Physics, University ofa few angstrom away from the lasing line at Hamburg,Germany,for the developmentof most549.7nm. parts of the experimental arrangement. ThisThere is no SE detectedwhen the crystal is cw work wassupportedby the DeutscheForschungs-pumped. Transitions terminating at high Stark gemeinschaft.levels of the ground state, which have lowBoltzmannpopulations,are heavily influencedbythecw ESA 113/2 —÷2H9 2 (seeFig. 1(c)) and,there- Referencesfore,will notexhibitcw-pumpedSEin any case.Weachievedquenchingof this ESA by co-dopingof an [1] L.F. JohnsonandH.J. Guggenheim,AppI. Phys.Lett. 20Er(2.0x 1020 cm ~):YAIO3 with Tb(0.2x 1020 (1972)474.cm 3). The energy transfer Er411312—~Tb7F0 [2] A.J. Silversmith, W. Lenth and R.M. Macfarlane, J.Opt. Soc. Am. A 3(1986)Pt28;AppI. Phys.Lett. 51(1987)reducesthe ‘i3/2 lifetime and,hence,the ESA to 1977.56% (4.3ms instead of 7.7 ms in Er (2.9X [3] W. Lenth, R.M. Macfarlane and A.J. Silversmith, Opt.1020cm ~):YA1O3), whereasthe4S3 2 lifetime re- News 13 (1987) 26.mainsnearlyunchanged(93u~versus102 us). [4] R.A. McFarlane,AppI. Phys. Lett. 54 (1989)2301.In conclusion,we measuredtime-resolvedand [5] P. Xie andS.C. Rand,Opt. Lett. 17(1992)1116:Opt. Lett.cw-pumpedexcited-stateabsorptionandstimulated 17 (1992) 1198.[6] T.J. Whitley, C.A. MiIIar, R. Wyatt, M.C. Brierley andD.emissionin Er3+ : YAIO1 at 550nm with a spectral Siehesta,Flectron I ett 27 (1991) 1785resolution of 0.4nm. The stimulated emission [7] J.Y. Allen, M. MonerieandH. Poignant,Electron. Lett. 28cross-sectionsderived from these measurements (1992) 111.are in good agreement with those obtained [8] R. Brede,T. Danger,E. Heumann,G. HuberandB. Chai,AppI. Phys.Lett., 63(1993)729.from absorption and fluorescencemeasurements, [9] RI. Laming, SB. Poole and E.J. Tarbox, Opt. Lett. 13which introduces a new measuringmethod for (1988) 1084.the precisedeterminationof absolutecross-sections [10] M. Pollnau,E. HeumannandG. Huber,AppI. Phys.A 54between two excited states. Stimulated emission (1992)404.at room temperatureon the4S3 2 —* 2 fluor- [11] S.A. Payne, L.L. ChaseandGD. Wilke, Phys.Rev. B 37(1988) 998.escenceat 550 nm exists up to 80 j.ts after pulsed [12] M. Pollnau, E. Heumannand G. Huber,Phys. StaI. Sol.excitation. A 130 (1992) K121

Stimulated emission and excited-state absorption at room temperature on the 550 nm-laser transition in Er<sup>3+</sup> doped YAlO<sub>3</sub>

NARCIS 

Stimulated emission and excited-state absorption at room temperature on the 550 nm-laser transition in Er3+ doped YAlO3

A 3(1986) Pt28;

are in good agreement with those obtained [8]

cw-pumped excited-state absorption and stimulated 17

emission in Er3 + :YAIO1 at 550 nm with a spectral Siehesta,

mains nearly unchanged (93u~ versus 102 us). [4] R.A.

ms instead of 7.7 ms in

not exhibit cw-pumped SE in any case. We achieved quenching ofthis ESA by co-doping ofan [1]

the precise determination of absolute cross-sections [10]

we measured time-resolved and [5]

which introduces a new measuring method for

Stimulated emission and excited-state absorption at room temperature on the 550 nm-laser transition in Er3+ doped YAlO3

Abstract

Similar works

Full text

Available Versions

University of Twente Research Information

NARCIS