Photorefractive properties of undoped,undoped, ceriumcerium-doped,-doped, and iron-dopediron -doped single-crystalsingle-crystal Sr0.6Ba0.4Nb2O6 Sr0

George A. Rakuljic Abstract. We present the results of our theoretical andand experimental studies of Amnon Yariv the photorefractivephotorefractive effect effect in in single single-crystal -crystal SBN:60, SBN:60, SBN:Ce, SBN:Ce, and and SBN:Fe. SBN:Fe. TheThe California Institute ofof TechnologyTechnology twotwo-beam -beam couplingcoupling coefficients,coefficients, response times,times, and absorption coefficients of Department of Applied Physics these materials areare given. Pasadena, California California 9112591125 Subject terms: photorefractive materials;materials; non nonlinear linear optical optical materials; materials; optical optical phase phase con con­ - Ratnakar Neurgaonkar jugation; imageimage processingprocessing; opticaloptical signal signal processing. processing. Rockwell International Corporation Optical Engineering 25(11), 12121212-1216 -1216 (November 1986).1986). Science Center Thousand Oaks,Oaks, CaliforniaCalifornia 9136091360

CONTENTS The point groupgroup symmetrysymmetry of of SBN SBN isis 44 mm,mm, whichwhich impliesimplies 1. IntroductionIntroduction that itsits electroelectro-optic -optic tensortensor is nonzero.nonzero. The dominant electro-electro- 2. MaterialMaterial propertiesproperties optic coefficientcoefficient is r33,r33 , which ranges from 100100 pm/pm/V V inin 3. PhotorefractivePhotorefractive properties SBN:25 to 14001400 pm/ V in SBN:75. In order toto realizerealize thethe largelarge 4. SummarySummary ofof resultsresults values of electro-opticelectro -optic coefficients in SBN crystals, they must, 5. ConclusionConclusion in practice, be poled by first being heated toto above their Curie 6. AcknowledgmentsAcknowledgments points and then being cooled to roomroom temperaturetemperature with an 7. ReferencesReferences applied dc electric field of 5 to 88 kVkV/cm. /cm. 1. INTRODUCTIONINTRODUCTION 3. PHOTOREFRACTIVEPHOTOREFRACTIVE PROPERTIES A givengiven photorefractivephotorefractive material is considered useful for opti­opti- Single crystals ofof SBN:60, SBN:60, SBN:Ce SBN:Ce (Sro (Sr^Bao^NbjCVCe), 6Bao 4Nb206:Ce), and cal processingprocessing applicationsapplications such as phase conjugate optics if itit SBN:Fe (Sr06Ba04Nb2O6:Fe)(Sr^Ba^NbjCVFe) grown grown atat RockwellRockwell Interna-Interna­ possesses threethree importantimportant features: low response time, large tional CorporationCorporation were were studied studied using using the the two two-wave -wave mixingmixing coupling coefficient, andand high optical quality. SpeedSpeed isis neces-neces­ experiment shownshown inin Fig.Fig. I1 toto determine determine their their effectiveness effectiveness asas sary if thethe crystalcrystal is toto be usedused in real-timereal -time applications, applications, and a photorefractive media. In Fig. 11 beamsbeams 11 andand 22 areare planeplane large photorefractive coupling coefficientcoefficient isis required forfor thethe waves thatthat intersect in the crystal and thus form an intensity construction ofof efficient devices. Regardless of itsits speedspeed and interference pattern. ChargeCharge isis excitedexcited byby thisthis periodicperiodic inten-inten­ gain, however, aa crystalcrystal withwith poorpoor optical quality is of little sity distribution into the conduction band,band, wherewhere itit migratesmigrates practical importance. Although a material is yet to be found under the influence of diffusion and drift inin thethe internalinternal elec-elec­ that completely satisfies allall threethree requirements, here we show tric fieldfield and thenthen preferentiallypreferentially recombinesrecombines with traps inin how well SBN:60SBN:60 approximatesapproximates them. regions of low irradiance. AA periodicperiodic spacespace chargecharge isis thusthus created that modulatesmodulates thethe refractiverefractive indexindex byby meansmeans ofof thethe 2. MATERIALMATERIAL PROPERTIES electroelectro-optic -optic effect. effect. This This indexindex grating,grating, being out of phasephase with the intensity distribution, introduces an asymmetry Strontium barium niobate (SBN) belongs to a class of with the intensity distribution, introduces an asymmetry that Strontium barium niobate (SBN) belongs to a class of allows one beam to be amplified by constructive interference tungsten bronze ferroelectrics that are pulled from a solid allows one beam to be amplified by constructive interference tungsten bronze ferroelectrics that are pulled from a solid with scattered by solution of alkalinealkaline earthearth niobates. The crystal isis transparenttransparent with light scattered by the gratinggrating whilewhile the otherother beambeam isis attenuated by destructive interference and can bebe grown with a varietyvariety ofof ferroelectricferroelectric andand electro-electro- attenuated by destructive interference withwith diffracteddiffracted light.light. This process is shown graphically in optic properties,properties, depending on the specific cationcation ratiosratios intro­intro- This process is shown graphically in Fig.Fig. 2.2. AlthoughAlthough itit isis implicitly assumed here that the only duced into the structure. InIn SBNSBN thethe unitunit cellcell containscontains 1010 implicitly assumed here that the only photocarriers inin SBN:60SBN:60 are electrons, it is acknowledged that holes NbO6 octahedra, with only five alkaline earth cations to fill 10 are electrons, it is acknowledged that holes maymay also partici-partici­ Nb06 octahedra, with only five alkaline earth cations to fill 10 pate in the photorefractive interstitial sites.1sites. 1 " -33 The The structurestructure is thus incompletelyincompletely filled,filled, pate in the photorefractive effect.effect. ExperimentsExperiments are currently under way to resolve this which permitspermits thethe additionaddition of aa widewide rangerange ofof dopants dopants intointo thethe under way to resolve this issue.issue. Mathematically, this two-beam coupling may be host crystal. TheThe general general formula formula for for SBN SBN is SrXBa1_XNb2O6,is SrxBa,_xNb2O6, Mathematically, this two -beam coupling may be described in the so SBN:60SBN:60 representsrepresents Sro Sr 066BaoBa04 4Nb2O6.Nb2O6. in the steadysteady statestate asas follows:follows:

dl1 III, Paper 21822182 received Aug. 13,13,1985; 1985; revisedrevised manuscript receivedreceived July 16,16,1986; 1986; = - r- all, (1)(I) accepted for publication JulyJuly 18,18,1986; 1986; received by Managing Editor JulyJuly 29,29, df 1986. ThisThis paperpaper isis aa revision of Paper 567567-04 -04 which was presented at the -I' SPIE conference on Advances in MaterialsMaterials forfor Active Active Optics,Optics, Aug.Aug. 2222-23, -23, 1985, SanSan Diego,Diego, Calif.Calif. TheThe paperpaper presented there appears (unrefereed) in dI2 IlI2 SPIE ProceedingsProceedings Vol.Vol. 567. d= T'I1+12r al,, (2) ©e 19861986 Society of Photo-OpticalPhoto -Optical Instrumentation Engineers.Engineers.

1212 / OPTICALOPTICAL ENGINEERING / / NovemberNovember 19861986 // Vol. 2525 No.No. 1111 Downloaded From: https://www.spiedigitallibrary.org/journals/Optical-Engineering on 7/10/2018 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use PHOTOREFRACTIVE PROPERTIESPROPERTIES OF OF UNDOPED,UNDOPED, CERIUM-DOPED,CERIUM -DOPED, ANDAND IRONIRON-DOPED -DOPED SINGLE-SINGLE -CRYSTAL Sr0.6Ba0.4Nb206

4

- 'e 33 E U tf 2

Z=d 2=0 z = d z 400 500 600 700760 800 Fig. 1.1. Experimental setup for twotwo-beam -beam coupling experiments. X(nm), (nm) Fig. 3.3. Absorption spectrum of SBN:Ce.

12

10io -

e8 - E U cos kx) `" 66 C 4

2

500 600 700 800 X(nm) n ~ rEsc Fig. 4.4. AbsorptionAbsorption spectrumspectrum ofof SBN:Fe.SBN:Fe.

Fig. 2. The photorefractive mechanism.mechanism. Two laserlaser beamsbeams intersect, forming an interference pattern. Charge is excited wherewhere thethe inten­inten- 0.30 sity is large andand migrates migrates to to regions regions of of low low intensity. intensity. TheThe electricelectric fieldfield associated withwith the resultant spacespace charge operates throughthrough the 0.25 electroelectro-optic -optic coefficientscoefficients to produce a grating. TE 0.20 o

t10.1500.15

where I)Ij and 12I2 are are thethe intensitiesintensities of beams 11 and 2 inside the O.IO0.10 coefficient, a crystal, respectively, Fr isis thethe twotwo-beam -beam coupling coefficient, a 0.05 is the absorption coefficient, and ¿f z/cos0j,z/ cos9i, wherewhere 0 0 < S fe < It - d d/cos0j. /cos9i. TheThe transienttransient behaviorbehavior isis approximated byby 400 500 600 700 800 X(nm) 1,(e;t) = (1 -e `ir)I1(e;t;t oo ) + e- `Irli(e;ttf ;t == 0),0), Fig. 5.5. Absorption spectrum of SBN:60.

(3) i =1,2, be obtained from the above equations. It is important toto notenote where r is a characteristic time constant andand that although thethe aboveabove description ofof the transient behavior is not strictlystrictly correct,4correct,4 it does indeed approximate thethe tem-tem­ I ¡(e;t 00)111,(e) (4) poral responseresponse ofof thethe twotwo-wave -wave mixing process in SBN very well since the measuredmeasured waveformswaveforms can bebe accuratelyaccurately de-de­ The solutions ofof thethe aboveabove coupledcoupled-wave -wave equations areare scribed by simple exponentials. Maximum couplingcoupling willwill result inin crystals with large PF but small a. However, a and I'F areare notnot independent.independent. InIn fact, fact, sincesince [I,(0) + 12(0)]e-4I2 (0)]e- charge must be excitedexcited into a conductionconduction band byby the intensity I(tS) = (5) II2(0)2 (0) interference pattern in order toto startstart thethe photorefractivephotorefractive pro-pro­ 1 +7^+ eertr This is precisely where the I1 cess, some absorptionabsorption isis necessary.necessary. This is precisely where the role of the dopant enters.enters. IfIf impuritiesimpurities areare purposelypurposely intro-intro­ duced into the crystal, donor sites are created that become thethe [I1(0) + 12(0)]e 't absorption centers.centers. ItIt must be noted,noted, however,however, that any I2(E) = (6) absorption that doesdoes notnot contributecontribute toto thethe photorefractive photorefractive 1, (0) I + e- rt mechanism is undesirable. 12 (0) Figures 3 and 4 show the effect of cerium and ironiron impuri-impuri­ ties on the absorption spectrumspectrum ofof undopedundoped SBN,SBN, whichwhich isis By measurement of the four intensitiesintensities I)I, (0),(0), I2(0),I2 (0), I)I, (£),(t), and given in Fig. 5. Several interesting observations cancan bebe made.made. 12(t),I2 (£), bothboth in the steady state and as a function ofof time,time, thethe First, thethe bandband edgeedge shiftsshifts fromfrom 400 400 nmnm inin SBN:60 SBN:60 toto 430430 nmnm two-beamtwo -beam coupling coupling coefficient coefficient F P and and thethe responseresponse timetime r can in SBN:Ce and 500500 nm inin SBN:SBN:Fe. Fe. Second, although the

OPTICAL ENGINEERING ENGINEERING / /November November 1986 1986 / / Vol.Vol. 2525 No.No. 1111 71213/ 1213 Downloaded From: https://www.spiedigitallibrary.org/journals/Optical-Engineering on 7/10/2018 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use RAKUUIC,RAKULJIC, YARIV, NEURGAONKAR

SBN:60 waswas notnot intentionallyintentionally doped, deepdeep-level -level impuritiesimpurities are limited use. evidenced by by perturbationsperturbations inin the spectrum near 550550 nm.nm. Another wayway PF can bebe modifiedmodified waswas suggestedsuggested inin Ref.Ref. 9.9. ByBy Finally, the effects of Ce and FeFe inin SBN:60SBN:60 are seenseen toto bebe varying the trap densitydensity NANA with reductionreduction andand oxidationoxidation significantly different. different. While While the the spectrum of SBN:CeSBN:Ce isis treatments, oneone should be able to controlcontrol'', F, as as shown shown in in Fig. Fig. 9.9. rather featureless, with a broad deepdeep levellevel centered at 480 nm,nm, Although the exact number density of traps isis difficultdifficult to the spectrumspectrum of SBN:SBN:Fe Fe displaysdisplays aa structured but broadbroad measure, we have indeed been able toto changechange thethe twotwo-beam -beam absorption extending from 500500 to 700 nm, with characteristic coupling coefficient fromfrom less thanthan 0.1 cm"cm-11 to 1515 cm-1cm"1 by peaks at 550 nm and 590 nm. Future investigationinvestigation ofof thesethese heating the crystal in atmospheres with different oxygen par­par- lines willwill indicate indicate whether whether or or notnot theythey contributecontribute to the pho- tial pressures. torefractive effect. The predicted variation ofof responseresponse time with trap density, First principle calculationscalculations usingusing thethe bandband transporttransport modelmodels5 which is shown in Fig. 10,10, has yet to be observed in SBN:Ce. can be usedused toto derivederive expressionsexpressions for FP and T.r. SolutionsSolutions toto thethe Although FF decreasesdecreases asas expectedexpected whenwhen thethe crystal crystal is is heatedheated inin photorefractive equations developed most fully by Kukhta- a reducing atmosphere,atmosphere, the time constantconstant remains unchanged rev6rev6-8 -8 show show that that F P andand rr can be represented functionally as at aa typicaltypical valuevalue ofof 100100 msms atat 11 W/W/cm cm22 irradiance.irradiance. ThisThis unexpected and currently unexplained resultresult hashas complicatedcomplicated TP =- P(dg, F(dg E0,, E0 ,X, X, T;T; r,r, ND, ND, NA,NA , e, n) , (7) our effort toto produceproduce aa cerium cerium-doped -doped SBNSBN photorefractivephotorefractive crystal with 1 ms response time, since heat treatment waswas rr= = T(dg, r(dg ,E0, E0, X,A, T, 10;I0; S,s, NA,NA> E)e) ,, (8) proposed as a method ofof achieving this goal.9goal.9 Therefore,Therefore, other where the experimentally controlled variables are techniques may need to be invokedinvoked to obtain thethe desireddesired speedspeed dgdg = gratinggrating periodperiod of response. EE00 == appliedapplied fieldfield (normal to gratinggrating planes)planes) Figures 11, 12, and 1313 show how the responseresponse time rr isis affected by changes in the mobility /z, the two-body recombi­ X == wavelength wavelength ofof incidentincident lightlight affected by changes in the mobility µ, the two -body recombi- nation rate yR,yR , andand thethe photoionizationphotoionization crosscross sectionsection s,s, T == temperature temperature respectively. SinceSince pµ isis predominantly predominantly anan intrinsicintrinsic quantityquantity of IOIQ = totaltotal irradianceirradiance the host crystal, little can be done to increaseincrease itsits value. How-How­ and the material parameters are ever, s andand 7yRR areare extrinsicextrinsic parametersparameters that cancan bebe varied by r = effectiveeffective electroelectro-optic -optic coefficient the selection ofof differentdifferent dopants.dopants. If the dopant chosenchosen hashas either a larger photoionization cross section or a smaller s = photoionizationphotoionization crosscross sectionsection either a larger photoionization cross section or a smaller 7yr == two two-body -body recombination recombination rate twotwo-body -body recombinationrecombination raterate coefficient than isis presentlypresently juµ == mobility mobility obtained with cerium, the resultingresulting dopeddoped samplesample ofof SBNSBN NDND = = number of donors under dark conditions should have a shortershorter responseresponse time.time. TheThe selectionselection ofof suchsuch aa NANA = = number of traps under dark conditionsconditions dopant, unfortunately, isis a nontrivial task. Table I showsshows thethe resultsresults ofof anan elemental elemental analysisanalysis byby e = staticstatic dielectricdielectric constant nuclear activation ofof undopedundoped andand cerium cerium-doped -doped SBN.SBN. SinceSince n == background background refractive refractive indexindex . undoped SBNSBN isis photorefractive whilewhile containingcontaining onlyonly tracetrace These equations were applied to ceriumcerium-doped -doped SBN. Specifi-Specifi­ quantities ofof cerium, we must conclude that cerium is not the cally, the sample contained 10181018 to 10191019 cm~ cm-33 ceriumcerium atoms,atoms, only photorefractive species for SBN. In fact, TableTable II indi-indi­ which resultedresulted inin anan as-grownas -grown crystal crystal with with F F == 1111 cm-1,cm"1 , cates that there are significant amounts ofof Fe,Fe, Ni,Ni, Mo, and Ta r == 0.10s, 0.10s,anda and a == 1.8 1.8cm- cm-1 1 atatio 10 = 11 WW/cm /cm2,T2 ,T == 298K,298 K, impurities inin the undoped SBNSBN crystal, and FeFe andand Ni,Ni, forfor X = 0.51450.5145 /zm,µm, EOE0 = = 0 V/cm,V/ cm, andand d dgg = = 55µm. /un. example, are known toto bebe effectiveeffective photorefractive centerscenters inin Variations inin FP andand r aboutabout thisthis "operating"operating point"point" are LiNbO3.10LiNbO3 . 10 Although Although iron iron hashas alreadyalready been used as a dopant shown in Figs. 6 through 13,13, along withwith thethe experimentallyexperimentally for SBN,SBN, thethe resultingresulting crystalscrystals werewere opticallyoptically imperfect.imperfect. obtained values of thethe twotwo-beam -beam coupling coefficientcoefficient and Therefore, wewe suggest that notnot onlyonly shouldshould the the study study of of iron iron- - response times forfor SBN:60 andand SBN:Ce. Data forfor SBN:SBN:Fe Fe are and ceriumcerium-doped -doped SBNSBN continue, but crystalscrystals dopeddoped withwith not shown since striationsstriations in the crystal so affectedaffected thethe opticaloptical other impurities, whichwhich maymay proveprove toto havehave betterbetter values values ofof yRyR quality of the crystalcrystal thatthat nono reliablereliable experimentalexperimental valuesvalues and s,s, shouldshould alsoalso bebe investigated.investigated. could be measured. Although the SBN:60 and SBN:CeSBNiCe sam­sam- ples werewere striationstriation freefree andand displayed good optical quality, to 4. SUMMARYSUMMARY OFOF RESULTSRESULTS date all of the SBN:FeSBN: Fe crystals,crystals, regardlessregardless ofof theirtheir Fe concen­concen- A major goal of our work has been the growth of high optical tration, havehave been severelyseverely marked with striations. WeWe believebelieve quality photorefractive SBNSBN crystals.crystals. ThisThis waswas accomplishedaccomplished that better control ofof thethe melt temperature willwill eliminate thisthis in part by growing striationstriation-free -free SBN:60 and SBN:Ce.SBNiCe. InIn fact,fact, problem. optically excellent crystals ofof SBN:60SBN:60 and SBN:CeSBN:Ce cancan now be With no applied field, Fig. 7 indicates that FF shouldshould bebe had as cubes approaching 11 cmcm onon aa side.side. SBN:Fe,SBNrFe, unfortu-unfortu­ greater than 11 cm-1cm"1 for allall practicalpractical valuesvalues ofof dg,dg, whilewhile the nately, has yet to bebe growngrown withoutwithout striations.striations. AsAs waswas indi-indi­ application of an electricelectric field of 2 kV/kV/cm cm ought to increase cated earlier, better control ofof thethe meltmelt temperaturetemperature maymay bebe the coupling coefficientcoefficient to to 35 35 cm" cm-11 at at d gdg = = 55µm, /xm, asas shown in necessary to eliminate this problem. Fig. 8. Such aa largelarge responseresponse would then make eveneven very thin Large twotwo-beam -beam couplingcoupling was observed in both SBN:60SBN:60 samples of SBN:Ce usefuluseful photorefractivephotorefractive media. However,However, and SBN:Ce.SBN:Ce. Values of FT rangedranged fromfrom 22 cm-1cm"1 inin SBN:60SBN:60 to in practice, these large values of F are not easilyeasily obtainable.obtainable. greater thanthan 1010 cmcm" -11 in SBN:Ce.SBN:Ce. SuchSuch responseresponse waswas largelarge As an electric field isis appliedapplied to the crystal, inducedinduced stressesstresses enough to permit thethe useuse ofof these crystals in the construction deform thethe material and the incidentincident beamsbeams are distorted.distorted. of the ring 11 and and semilinear semilinear 1212 passive passive phase phase conjugate conjugate , mirrors, Therefore, we concludeconclude that the application of of an an electricelectric fieldfield for example. It was also found that oxidationoxidation andand reductionreduction to the crystal to control itsits twotwo-beam -beam coupling coefficientcoefficient isis of techniques served as effective methods for varying the value of

1214 / OPTICAL OPTICAL ENGINEERING / / NovemberNovember 19861986 / Vol.Vol. 2525 No.No. 1111 Downloaded From: https://www.spiedigitallibrary.org/journals/Optical-Engineering on 7/10/2018 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use PHOTOREFRACTIVE PROPERTIES OFOF UNDOPED,UNDOPED, CERIUM-DOPED,CERIUM -DOPED, ANDAND IRONIRON-DOPED -DOPED SINGLE-CRYSTALSINGLE -CRYSTAL SrSr0.6Ba04Nb2060.6 Bao.4Nb2O6

40 1 20 r I 1 I A«e = SBN:60 o*o = SBN:CeSBNiCe A =SBN:60 o SBN:Ce 303O e e 15I5 ee o - ^o o o T yU T E 20 E 10IO o ... .01 5 10

e ee e A A .0010.001 I I 2 4 6 8 10 00 2 4 6 8 10 00 2 4 6 8 (010 d (pm) d9 (p.m) d9(µm) Fig. 6. ResponseResponse time versus grating period Fig. 7.7. Coupling coefficient versusversus gratinggrating Fig. 8. CouplingCoupling coefficientcoefficient versusversus gratinggrating at Ilo0 = 11 WW/cm /cm22 forfor EE00 == 0 VV/cm. /cm. period forfor EE00 == 0 VV/cm. /cm. period forfor EE00 == 22 kVkV/cm. /cm.

IOOO1000 1000 IOO100

100IOO 100

10 10 I

'E ! .i.1

o .01 ; .01 H .1

.001.00! .01 .000!.0001

IE-5IE-5 .001

1 I IE-6 1 1 I IE 61E13 00011E-5.0001 .0!OIE13 1E16IEI8 1E19IEI9 W IEI3 1E14IEI4 1E15IEI5 IEI61E16 ZEITIEI7 1 10 1001000 1E4 1E5 "IEI3 IEI4 IEI51E15 IEI6IE16 IEIEIT I? 1E18IEI8 IEI91E19 .001 .01 1E14 NA(cm'3) NA(cmNA(crrf 3)3) N A(Cm 3) (cm3'Vsec) Fig. 9. CouplingCoupling coefficient versus versus trap den­den- Fig. 10. ResponseResponse time versus trap density Fig. 11.11. Response timetime versus mobility atat sity for EE00 == 0 V/cmV /cm andand dg d9 = = 55µm. ^im. at loI 0 == 11 WW/cm /cm2,2 , assumingassuming µp = Ilo0 = 11 WW/cm /cm2,2, assumingassuming NANA = 10181016 cm-3,cm""3, 0.1 cm2cm2 -V-V -11 -s-s 1,1 , YR7R == 5X105X10- -88 cm3crnVs, /s, TR)1 == 5X105X10- -88 cm3cm*/s.s /s,s == 1.6X10- I.eXI 79cm2, s = 1.6X10- 19cm2,ND == 10791019 cm-3,cm-3,and and NoND == 10191019 cm-3,cm~3, and dd9fl == 5µm.5 Mm. dd9g == 55µm.

10 IOOO1000

IOO100

10 ) I Ñ N : .i.1 F .01

.01.0)

.001 .001.00!

I 1 1 1 .000!.0001 ' .00011E-22.000! IE-12 IIE- E -I I IE-101E-10 IE-9I E -9 IE-8I E- 6 IE-TIE-7 IE-6IE -6 IE-22 IE-21 IE-20IE-20 IE-19IE -19 IE-18IE -16 IE-17IE- IT IE-16 Yrt(cm3/ R(cm3/sec) /sec) s(cm2)s(cm2) Fig. 12. ResponseResponse timetime versusversus two-bodytwo -body recombination recombination raterate coeffi­coeffi- Fig. 13. ResponseResponse time versus photoionization crosscross sectionsection atat 10I0 == cient at Il00 = 11 WW/cm /cm2,2 , assuming NNAA == 10761016 cm~CM-3,3, M µ == 0.1 cm2cm2 1 WW/cm /cm2,2 , assumingassuming N NAA = = 10101616 cm~ cm3 -3,, M µ= =0.1 0.1 cmcm2V-2 -V- 11s-1,-s-1 , V-1V-i. ss -1,1 ,s s == 1.6X10-19 1.6X10-19 cm2,cm2 ,N NoD == 1019 1019 cmcm" -3,3 , andand dg dg = = 55µm. ^m. 7YRR == 5X105X10~ -88 cm3cmVs, /s, NN0D = 10791019 cmcm~ -3,3, and and d deg = = 55µm. Mm.

TF in these crystals. However, thethe application of an external 5. CONCLUSIONSCONCLUSIONS electric fieldfield toto thethe crystals tendedtended to degrade their opticaloptical High optical quality undopedundoped and and doped doped single single-crystal -crystal SBN:60SBN:60 quality ratherrather than improveimprove the valuevalue ofof theirtheir couplingcoupling has been grown and proved to be photorefractive. ThisThis effect coefficients. was quantified by measuringmeasuring thethe couplingcoupling coefficientscoefficients and The response times of thethe SBN crystals we testedtested averagedaveraged response times of severalseveral samplessamples usingusing thethe methodmethod ofof two two- - about 100100 ms for anan incidentincident irradianceirradiance ofof 11 WW/cm /cm2.2 . InIn wave mixing. TheThe resultsresults of thisthis workwork indicate that the intro­intro- general, SBNiCeSBN:Ce respondedresponded quicker than SBN:60, with times duction ofof dopantsdopants intointo SBN:60SBN:60 producesproduces crystalscrystals withwith anan approaching 5050 ms at 11 W/ cmcm2.2 . SinceSince thethe two-beamtwo -beam couplingcoupling even greater photorefractive effect than that ofof undopedundoped coefficient ofof SBNiCeSBN:Ce isis so so large, large, thethe timetime requiredrequired to reach a SBN:60. given diffractiondiffraction efficiency withwith SBN:CeSBN:Ce willwill bebe much much shortershorter 6. ACKNOWLEDGMENTS than that needed with SBN:60. AlthoughAlthough the response timetime ofof 6. ACKNOWLEDGMENTS SBN:Fe hashas yetyet toto bebe reliablyreliably determined,determined, we believebelieve thatthat its This research was supported by grants from RockwellRockwell Inter-Inter­ speed will notnot differdiffer significantlysignificantly from from thatthat ofof thethe other two national Corporation, thethe U.S.U.S. AirAir Force Force Office Office ofof ScientificScientific crystals. Research, and the U.S.U.S. ArmyArmy ResearchResearch Office.Office.

OPTICAL ENGINEERINGENGINEERING / /November November 1986 1986 / / Vol.Vol. 2525 No. 1111 // 12151215 Downloaded From: https://www.spiedigitallibrary.org/journals/Optical-Engineering on 7/10/2018 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use RAKULJIC, YARIV, NEURGAONKAR

TABLE I,I. Elemental analysis byby weightweight of SBN:60 andand SBN:Ce.SBN:Ce. George A.A. RakuljicRakuljic was was born born in in Chicago, Chicago, III., 111., onon Sept. 1, 1961.1961. AfterAfter threethree yearsyears ofof under-under­ Elements graduategraduate study atat the UniversityUniversity ofof California,California, & Units SBN:60 SBN:Ce LosLos Angeles, hehe receivedreceived thethe M.S.M.S. degreedegree inin electricalelectrical engineeringengineering fromfrom thethe CaliforniaCalifornia Insti-Insti­ tutetute ofof Technology, Pasadena, inin 1983, wherewhere PPM < 0.10. < 0.10.1 uU 1 he is currentlycurrently pursuingpursuing thethe Ph.D.Ph.D. degreedegree inin TH PPM < 0.30. 3 < 0.20.2 electricalelectrical engineering.engineering. NA PPMPPM 30.030. 0 <30.0 His current researchresearch interestsinterests areare photore-photore­ SC PPM 0.040. 04 0.04 CR PPM < 5.05. 0 < 5.05.0 fractivefractive materials,materials, phase phase conjugateconjugate optics,optics, andand optical informationinformation processing.processing. FE %% 0.0290. 029 0.014 CO PPM 0.30. 3 0.3 NI PPM 50.050. 0 50.0 ZN PPM 7.07. 0 5.0 Amnon Yariv,Yariv, aa nativenative of of Israel, Israel, obtainedobtained thethe AS PPM < 1.01. 0 < 1.0 I B.S. degree in 1954, the M.S.M.S. degreedegree inin 1956,1956, § J and the Ph.D.Ph.D. degree in 19581958 inin electricalelectrical SE PPM < 5.05. 0 < 5.0 11 II III I engineering from thethe UniversityUniversity ofof CaliforniaCalifornia BR PPM < 0.50. 5 < 0.5 inin Berkeley.Berkeley. MO PPM 11.11.00 4.0 He wentwent to the Bell Telephone Laboratories, SB PPM 0.0.55 0.5 Murray Hill, N.J.,N.J., in 1959,1959, joiningjoining thethe earlyearly < 0.2 CS PPM < 0.2 < 0.2 stages of the laser effort. He joined the Califor-Califor­ nia Institute of of Technology Technology in in 1964 1964 as as an an asso-asso­ 160000.0 150000.0 BA PPM ciate professorprofessor ofof electricalelectrical engineering,engineering, LA PPM 0.2 1.0 LA PPM becoming aa professor inin 1966. In 19801980 hehe HF PPM < 0.20.2 < 0.20.2 HF PPM Engineering and TA PPM 1212.0 . 0 13.0 became the Thomas G. Myers Professor of Electrical Engineering and W PPM < 3.03.0 1.0 Applied Physics.Physics. On the technical side, he took part (with various coworkers)coworkers) in the AU PPB < 5.0 5.0 discovery of a number of early solid-statesolid -state systems,systems, in thethe formula­formula- CE PPM < 1.01.0 47.0 tion ofof thethe theorytheory ofof parametricparametric quantumquantum noisenoise andand thethe predictionprediction ofof ND PPM Interfer Interfer parametric fluorescence, in thethe inventioninvention ofof the the technique technique of of mode mode- - SM PPM 0.01 0.32 locked ultrashort-pulseultrashort -pulse lasers and and FM FM lasers,lasers, in in thethe introduction of EU PPM 0.07 0.10 GaAs and CdTe as infrared electroelectro-optic -optic andand windowwindow materials, in proposing andand demonstratingdemonstrating semiconductorsemiconductor-based -based integratedintegrated opticsoptics TB PPM < 0.1 < 0.1 technology, and inin pioneering thethe fieldfield ofof phase phase conjugateconjugate optics.optics. YB PPM < 0.050.05 0.05 His present research efforts are inin thethe areasareas ofof nonlinearnonlinear optics,optics, LU PPM < 0.010.01 < 0.01 semiconductor lasers,lasers, and integrated optics,optics, especiallyespecially the problemproblem of SR PPM 148000.0 135000.0 monolithic integrationintegration ofof transistors,transistors, injectioninjection lasers, lasers, andand detectorsdetectors for RB PPM < 5.0 < 5.0 high frequencyfrequency applicationsapplications andand ultrafastultrafast (10 (10~ -1212 s)s) semiconductorsemiconductor devices and phenomena. Professor YarivYariv hashas publishedpublished widelywidely in the laserlaser andand optics fields (some 300300 papers) andand hashas written written a number of basic textstexts inin quantumquantum electronics, optics, and quantumquant urn mechanics.mechanics. HeHe isis anan associate editor of Optics Communications and was previously associate editor of the Journal ofof Quantum ElectronicsElectronics and and the the JournalJournal of of Applied Applied Physics. Physics, HeHe is a member of thethe AmericanAmerican PhysicalPhysical Society,Society, PhiPhi BetaBeta Kappa,Kappa, thethe 7. REFERENCESREFERENCES American Academy of Arts andand Sciences, and the National Academy of 1. P. B. Jamieson, S. C. Abrahams, and J.J. L.L. Bernstein,Bernstein, "Ferroelectric"Ferroelectric Engineering andand aa FellowFellow ofof thethe IEEEIEEE and OSA. He received the 19801980 tungsten bronzebronze-type -type crystal crystal structures. structures. I.I. Barium strontium niobateniobate Quantum ElectronicsElectronics AwardAward ofof the the IEEE, IEEE, the 19851985 UniversityUniversity of of Penn- Penn­ Bao.27Sro.75.Nb2O5.78,"Bao27Sr075Nbz0578," J. Chem. Phys.Phys. 48,48, 50485048 (1968).(1968). sylvania PenderRender Award, andand thethe 19861986 OSA OSA Ives Ives Medal.Medal. HeHe isis aa founder 2. P. B. Jamieson, S. C. Abrahams,Abrahams, andand J.J. L.L. Bernstein, Bernstein, "Ferroelectric "Ferroelectric and chairman ofof thethe boardboard ofof ORTEL ORTEL Corp.Corp. tungsten bronze-typebronze -type crystal crystal structures. structures. II. II. Barium sodium niobate BaBa(4(4 +x)+z)Na Na(2_2X)(2-2X)Nb Nó10030,"10O30," J. Chem.Chem. Phys.Phys. 50,50, 43524352 (1969).(1969). 3. S. C. Abrahams, P. B.B. Jamieson,Jamieson, andand J.J. L.L. Bernstein, Bernstein, "Ferroelectric"Ferroelectric tungstentungsten bronze-typebronze -type crystal crystal structures. structures. III.III. Potassium lithium niobate KK(6(6_ -xx_ y)-y)Li<4 Li+x) 4 +X)Nb((oNb(1Q+y) 0+y)03o,"30,"J. Chem.J. Chem. Phys. Phys. 54, 54, 23552355 (1971). Ratnaker R.R. NeurgaonkarNeurgaonkar is is manager manager ofof thethe 4. J.J. M. M. Heaton Heaton and and L. L. Solymar, Solymar, "Transient "Transient energy energy transfertransfer duringduring holo-holo­ Ferroelectric Materials DepartmentDepartment atat thethe gram formation inin photorefractive crystals, crystals,"Opt. "Opt. Acta Acta 32(4), 32(4), 397 397 (1985).(1985). Rockwell International ScienceScience Center.Center. HeHe 5. G.G. C.C. ValleyValley and M.M. B.B. Klein,Klein, "Optimal"Optimal propertiesproperties ofof photorefractive photorefractive materials for optical data processing,"processing," Opt.Opt. Eng.Eng. 22(6), 22(6), 704 704-711(1983). -711(1983). receivedreceived the B.Sc. degree withwith honors in 1962, 6. N.N. V.V. Kukhtarev,Kukhtarev, V.V. B.B. Markov, andand S.S. G.G. Odulov,Odulov, "Transient"Transient energyenergy the M.Sc.M.Sc. degreedegree inin 1963,1963, andand thethe Ph.D.Ph.D. transfertransfer during hologram formation inin LiNbO3LiNbO3 inin external electric field," degree in 19671967 inin solidsolid-state -state chemistrychemistry fromfrom Opt. Commun.Cornmun. 23,23, 338 (1977). Poona University, India.India. At Rockwell, Dr. Neur­Neur- 7. N.N. V.V. Kukhtarev, V. B. Markov, S. G.G, Odulov, M.M. S.S. Soskin,Soskin, and V.V. L. gaonkar has been directingdirecting thethe ferroelectricferroelectric Vinetski, "Holographic"Holographic storagestorage in electroopticelectrooptic crystals. I. Steady state," materials researchresearch andand developmentdevelopment programprogram Ferroelectrics 22, 949 (1979),(1979). for various devicedevice applications, includingincluding elec-elec­ 8. N.N. V.V. Kukhtarev,Kukhtarev, "Kinetics of hologram recording and erasure inin elec-elec­ tro-tro-optic, optic, photorefractive,photorefractive, pyroelectric imagers,imagers, trooptictrooptic crystals," Sov. Tech. Phys.Phys. Lett.Lett. 2,2, 438438 (1976).(1976). 9. G.G. A.A. Rakuljic,Rakuljic, A. Yariv, and R.R. R.R. Neurgaonkar,Neurgaonkar, "Photorefractive"Photorefractive surface acoustic wave, millimeter wave,wave, andand piezoelectricpiezoelectric transducers. properties of ferroelectric BaTiO3BaTiO3 and SBN:60,SBN:60," " in andand He and a coworker have developed variousvarious growth techniques forfor fer-fer­ Applications, P. Yeh,Yen, ed., Proc.Proc. SPIESPIE 613, 613, 110 110-118 -118 (1986).(1986). roelectric crystalscrystals/films /films andand recentlyrecently successfullysuccessfully demonstrateddemonstrated thethe 10. W. Phillips, J.J. J. Amodel, and D. L. Staebler, "Optical and holographic growth ofof opticaloptical-quality -quality dopeddoped andand undopedundoped SSr, r1 _ ,BaNb206xBaxNb2O6 and and BSKNN BSKNN storagestorage propertiesproperties ofof transitiontransition metal dopeddoped lithium niobate," RCA Rev. single crystals usingusing thethe CzochralskiCzochralski technique.technique. BesidesBesides ferroelectric 33,94(1972).33, 94 (1972). materials, Dr. Neurgaonkar has been interested in magnetics, lumines-lumines­ 11. M.M. CroninCronin-Golomb, -Golomb, B.B. Fischer, J.J. O. White,White, andand A.A. Yariv,Yariv, "Passive"Passive cence, and laser crystal development work. HeHe isis a member of various phasephase conjugate based onon selfself-induced -induced oscillation in an opticaloptical professional societies, including the AmericanAmerican CeramicCeramic Society, the ring cavity," Appl. Phys.Phys, Lett.Lett. 42,42, 919919 (1983).(1983). Electrochemical Society, and the American Association forfor CrystalCrystal 12. M. CroninCronin-Golomb, -Golomb, B.B. Fischer,Fischer, J.J. O. White,White, andand A.A. Yariv,Yariv, "Passive"Passive Electrochemical Society, and the American Association (self-pumped)(self -pumped) phase phase conjugate conjugate mirror:mirror: theoretical and experimentalexperimental Growth. He is the authorauthor oror coauthorcoauthor ofof moremore thanthan 7070 research research investigation,"investigation," Appl.Appl. Phys. Lett. 41,41, 689689 (1982). 3 publications.

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