The lasing performance and wavelength tunability of a novel high efficiency copolymer poly[(2,5,2",5"-tetraoctyl)-p-terphenyl-4,4"-ylene vinylene-p-phenylene vinylene], TOP-PPV, pumped with third harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The results were compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimental conditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyes with more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelength region between 414 and 456 nm (Δλ=38 nm).

Brouwer, Hendrik-Jan,

Hadziioannou, George,

Hilberer, Alain,

Krasnikov, Victor V.,

Wildeman, Jurjen,

Brouwer, H. J.

Krasnikov, V. V.

Hilberer, A.

Wildeman, J.

Hadziioannou, G.

University of Groningen

   University of GroningenNovel high efficiency copolymer laser dye in the blue wavelength regionBrouwer, H. J.; Krasnikov, V. V.; Hilberer, A.; Wildeman, J.; Hadziioannou, G.Published in:Applied Physics LettersDOI:10.1063/1.113368IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Brouwer, H. J., Krasnikov, V. V., Hilberer, A., Wildeman, J., & Hadziioannou, G. (1995). Novel highefficiency copolymer laser dye in the blue wavelength region. Applied Physics Letters, 66(25), 3404-3406.https://doi.org/10.1063/1.113368CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 25-04-2023Novel high efficiency copolymer laser dye in the blue wavelength regionHendrik-Jan Brouwer, Victor V. Krasnikov, Alain Hilberer, Jurjen Wildeman,and George HadziioannouPolymer Chemistry Department, Material Science Centre, State University Groningen, Nyenborgh 4,9747 AG Groningen, The Netherlands~Received 30 November 1994; accepted for publication 21 April 1995!The lasing performance and wavelength tunability of a novel high efficiency copolymer poly@~2, 5,29, 59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#, TOP-PPV, pumped withthird harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The resultswere compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimentalconditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyeswith more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelengthregion between 414 and 456 nm~Dl538 nm!. © 1995 American Institute of Physics.er,he.wasaseres andwasinyesr inIn 1990, research in the field of semiconducting congated polymers led to the introduction of the first polymlight emitting diodes based on poly@p-phenylene vinylene#.1,2This observation of electroluminescence triggered intensresearch by numerous groups and resulted in the elaboraof various other semiconducting polymer light emitting dode ~LED! devices with impressive efficiency3 and colortunability.4,5 It was realized that the high photoluminescenquantum yield of conjugated polymers made them promiscandidates for active laser media in the liquid or solid staFurthermore, due to their good processability and mechcal properties, polymeric dyes have a potential advantagactive gain media in dye doped polymeric optical devicLaser action of a semiconducting polymer~MEH-PPV! inthe liquid state6,7 operating in the yellow/red wavelength region was achieved for the first time in 1992. The reportlasing performance of this polymer was comparable to tof the most efficient laser dye Rhodamine 6G.In this letter we demonstrate for the first time the lasiperformance of a novel highly efficient copolymepoly@~2,5,29,59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#,8 TOP-PPV, in the blue wavelengthregion. In Fig. 1~inset top right! the structure of the repeaunit is given. The TOP-PPV copolymer~Mn52.63103, Mw54.53103) has a well-defined conjugatebackbone, consisting of regularly alternating terphenyle~TOP! andp-phenylene-vinylene~PPV! blocks. The presenceof four octyl side chains provides solubility of the conjugatform in common polar solvents such as tetrahydrofur~THF! and chloroform. The polymer exhibits a high thermstability, up to 420 °C under nitrogen. Figure 1 shows tabsorbance ~lmax5357 nm! and emission (lmax5440 nm) spectra of a solution of the TOP-PPV copolymin hexane~10 mm quartz cell!. Photoluminescence quantumyields as high asMF;0.8–0.9 were obtained in solution8~THF, hexane! which gave a clear indication of the possibiity of lasing action.The energy conversion efficiency measurements wperformed using a linear nondispersive cavity in a quasilgitudinal pumping arrangement. The experimental setupschematically depicted in Fig. 2. The cavity is defined byconcave metallic rear mirror and a flat dielectric output co3404 Appl. Phys. Lett. 66 (25), 19 June 1995 0003-6951Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjeju-erivetioni-ceingte.ani-e ases.-edhatngrtdneedanalheerl-ereon-isau-pler ~transmittanceT581%,l5360–460 nm! separated by adistance of 95 mm. The pump source was a Nd:YAG lasQuanta-Ray GCR 130-50, operating at tripled frequency~l5355 nm,p-polarized, pulse width58 ns! with a repetitionrate of 1 Hz. In order to prevent laser generation from tcell walls and to minimize Fresnel losses, the dye cell~pathlength 10 mm! was tilted with respect to the pumping beamThe angle between the pumping and generated beamapproximately 7°. The input and output pulse energy wmonitored with two calibrated pyroelectric detectors~Coher-ent LMP 5, Molectron J3-02, respectively!. The spectralcharacteristics of the laser and luminescence output wmeasured with an Optical Multichannel Analyzer~PrincetonInstruments!. In the case of the tuning range measurementquartz prism was incorporated between the rear mirror athe dye cell as a dispersive element. Wavelength tuningachieved by rotation of the rear mirror.The lasing performance of TOP-PPV was studiedthree solvents; tetrahydofuran, hexane, andp-xylene~Merck,spectroscopic grade!. In the case of hexane~a poor solventfor TOP-PPV! the solution was filtered over an 0.2mm filterto remove undissolved compound. The reference laser dFIG. 1. Absorbance and emission spectra of the TOP-PPV copolymehexane. Inset~top right-hand side!: the chemical structure of the TOP-PPVrepeat unit./95/66(25)/3404/3/$6.00 © 1995 American Institute of Physicsct¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspnn-r--lb-sein-dnfi-ter-dCoumarin 120 and 47~Lambdachrome LC 4400 and LC4700! were used in ethanol solution~Merck, spectroscopicgrade!. All prepared solutions had a transmittance of 1%l5355 nm, measured in a standard 10 mm quartz cuvettea SLM aminco 3000 diode array spectrometer. Concentratdependent measurements at fixed pump energy indicatedthe transmittance~T51%! of the dye solutions were in theregion of optimum efficiency.Clear evidence of laser action of the TOP-PPV copolmer is shown in Fig. 3. When the pump energy exceedsthreshold energy of lasing, intense blue light with a narrospectral bandwidth@7 nm, full width at half-maximum~FWHM!# was emerging from the output coupler. The spetrum of the spontaneous emission was obtained after bloing the rear mirror of the cavity to interrupt the feedbacsystem. The wavelength of laser generation coincides wthe maximum of the fluorescence emission spectrum.Figure 4 shows the ordinary linear dependence of toutput pulse energy of the dyes as function of the input puenergy of the Nd:YAG laser. This plot clearly demonstratthat the conversion efficiency~7%! of TOP-PPV in hexane isFIG. 2. Experimental setup: L, lens; BS, beam splitter; PD, pyroelectdetector; RM, concave rear mirror; C, flow cell; and OM, dielectric outpmirror.FIG. 3. Spontaneous~dotted! and stimulated~solid! emission spectra ofTOP-PPV in hexane as measured with the linear nondispersive cavity.Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecatonionthaty-thewc-ck-kithhelseessignificantly higher than in all other cases. The conversioefficiencies and lasing wavelengths for all dyes are given iTable I. The efficiencies of TOP-PPV in THF andp-xylene~1.8% and 2.8%, respectively! are comparable to that of thecoumarin dyes. As expected, the lasing wavelength for TOPPPV in THF andp-xylene are red shifted~bathochromicshift! with respect to hexane due to increasing solvent polaity. The lasing bandwidth of the TOP-PPV polymer was approximately 7 nm in all solvents. The bandwidth of bothcoumarin dyes was almost twice larger, 12 nm. During almeasurements no visible signs of photodegradation were oserved.The results of the wavelength tunability measurementare shown in Table I. For the TOP-PPV copolymer in hexanthe tuning curve and the fluorescence spectrum are plottedFig. 5. From this plot it can be seen that the tuning curvefollows the shape of the emission spectrum in the wavelength region with the highest emission cross section~414–452 nm!, due to the small overlap between absorbance anemission band. The wavelength tuning range of TOP-PPV ihexaneDl538 nm! was the highest among all dye/solventsystems measured, which demonstrated the superior efciency of this polymer solution. It should be mentioned thathe bandwidth of laser generation was 3 nm~FWHM! in allricutFIG. 4. Plot of the output pulse energy of the dye laser as funciton of thinput pulse energy of the Nd:YAG pump beam in case ofm, TOP-PPVcopolymer in hexane;h, TOP-PPV copolymer inp-xylene; andd, Cou-marin 120 in ethanol. The slope of the lines represents the energy convesion efficiency.TABLE I. Comparison of the laser characteristics of Coumarin 47, 120, anTOP-PPV.Dye Solventl lasa~nm!Efficiencya~%!Tuning rangeb~nm!TOP-PPV THF 449 1.8 438–456p-xylene 449 2.8 436–456hexane 440 6.8 414–452Coumarin 47 ethanol 451 2.8 444–470Coumarin 120 ethanol 439 2.3 424–450aLinear nondispersive cavity.bDispersive cavity.3405Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspf--e--,cases and was mainly determined by the dispersion ofcavity.The reason for the higher conversion efficiency of TOPPPV in hexane is unclear at this moment. Gel permeatichromatography~GPC! of the solution revealed that the mo-lecular weight distribution changed with respect to THF anp-xylene. Due to the poor solubility in hexane, only thlower molecular weight species dissolved and as a resultFIG. 5. Tuning curve~-j-! and luminescence spectrum~dashed! of theTOP-PPV copolymer in hexane~pump energy 10 mJ!.3406 Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecthe-ondethepolydispersity (Mw /Mn) decreased from 1.7~in THF! to1.17 (Mn53.13103, Mw53.63103).In conclusion, we have demonstrated the performance oa novel high efficiency copolymer laser dye in the bluewavelength region. The conversion efficiency when pumpedby third harmonic radiation of a Nd:YAG laser exceeds thatof the well-known coumarin dyes in this wavelength region.In the case of the TOP-PPV copolymer in hexane a wavelength tuning range of almost 40 nm was obtained. The lasing performance of this polymer shows considerable promisfor the development of stable solid-state dye doped laser materials based on TOP-PPV. This research was financially supported by SON/STW and by the EEC~Human Captial andMobility program!.1J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Nature~London!347, 539 ~1990!.2D. Braun and A. J. Heeger, Appl. Phys. Lett.58, 1982~1991!.3N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, and A. B.Holmes, Nature~London! 365, 628 ~1993!.4G. G. Malliaras, J. K. Herrema, J. Wildeman, R. H. Wieringa, R. E. Gill,S. S. Lampoura, and G. Hadziioannou, Adv. Mater.5, 721 ~1993!.5R. E. Gill, G. G. Malliaras, J. Wildeman, and G. Hadziioannou, Adv.Mater.6, 132 ~1994!.6D. Moses, Appl. Phys. Lett.60, 3215~1992!.7D. Moses, U. S. Patent No. 5,237,582 A~1992!.8A. Hilberer, J. Wildeman, B. J. van der Scheer, and G. HadziioannouMacromolecules28, No. 13 ~1995!.Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jsp

English

Novel high efficiency copolymer laser dye in the blue wavelength region

   University of GroningenNovel high efficiency copolymer laser dye in the blue wavelength regionBrouwer, H. J.; Krasnikov, V. V.; Hilberer, A.; Wildeman, J.; Hadziioannou, G.Published in:Applied Physics LettersDOI:10.1063/1.113368IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Brouwer, H. J., Krasnikov, V. V., Hilberer, A., Wildeman, J., & Hadziioannou, G. (1995). Novel highefficiency copolymer laser dye in the blue wavelength region. Applied Physics Letters, 66(25), 3404-3406.https://doi.org/10.1063/1.113368CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-11-2019Novel high efficiency copolymer laser dye in the blue wavelength regionHendrik-Jan Brouwer, Victor V. Krasnikov, Alain Hilberer, Jurjen Wildeman,and George HadziioannouPolymer Chemistry Department, Material Science Centre, State University Groningen, Nyenborgh 4,9747 AG Groningen, The Netherlands~Received 30 November 1994; accepted for publication 21 April 1995!The lasing performance and wavelength tunability of a novel high efficiency copolymer poly@~2, 5,29, 59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#, TOP-PPV, pumped withthird harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The resultswere compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimentalconditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyeswith more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelengthregion between 414 and 456 nm ~Dl538 nm!. © 1995 American Institute of Physics.In 1990, research in the field of semiconducting conju-gated polymers led to the introduction of the first polymerlight emitting diodes based on poly@p-phenylene vinylene#.1,2This observation of electroluminescence triggered intensiveresearch by numerous groups and resulted in the elaborationof various other semiconducting polymer light emitting di-ode ~LED! devices with impressive efficiency3 and colortunability.4,5 It was realized that the high photoluminescencequantum yield of conjugated polymers made them promisingcandidates for active laser media in the liquid or solid state.Furthermore, due to their good processability and mechani-cal properties, polymeric dyes have a potential advantage asactive gain media in dye doped polymeric optical devices.Laser action of a semiconducting polymer ~MEH-PPV! inthe liquid state6,7 operating in the yellow/red wavelength re-gion was achieved for the first time in 1992. The reportedlasing performance of this polymer was comparable to thatof the most efficient laser dye Rhodamine 6G.In this letter we demonstrate for the first time the lasingperformance of a novel highly efficient copolymerpoly@~2,5,29,59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#,8 TOP-PPV, in the blue wavelengthregion. In Fig. 1 ~inset top right! the structure of the repeatunit is given. The TOP-PPV copolymer ~Mn52.63103, Mw54.53103) has a well-defined conjugatedbackbone, consisting of regularly alternating terphenylene~TOP! and p-phenylene-vinylene ~PPV! blocks. The presenceof four octyl side chains provides solubility of the conjugatedform in common polar solvents such as tetrahydrofuran~THF! and chloroform. The polymer exhibits a high thermalstability, up to 420 °C under nitrogen. Figure 1 shows theabsorbance ~lmax5357 nm! and emission (lmax5440 nm) spectra of a solution of the TOP-PPV copolymerin hexane ~10 mm quartz cell!. Photoluminescence quantumyields as high as MF;0.8–0.9 were obtained in solution8~THF, hexane! which gave a clear indication of the possibil-ity of lasing action.The energy conversion efficiency measurements wereperformed using a linear nondispersive cavity in a quasilon-gitudinal pumping arrangement. The experimental setup isschematically depicted in Fig. 2. The cavity is defined by aconcave metallic rear mirror and a flat dielectric output cou-3404 Appl. Phys. Lett. 66 (25), 19 June 1995 0003-6951Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬supler ~transmittance T581%, l5360–460 nm! separated by adistance of 95 mm. The pump source was a Nd:YAG laser,Quanta-Ray GCR 130-50, operating at tripled frequency ~l5355 nm, p-polarized, pulse width58 ns! with a repetitionrate of 1 Hz. In order to prevent laser generation from thecell walls and to minimize Fresnel losses, the dye cell ~pathlength 10 mm! was tilted with respect to the pumping beam.The angle between the pumping and generated beam wasapproximately 7°. The input and output pulse energy wasmonitored with two calibrated pyroelectric detectors ~Coher-ent LMP 5, Molectron J3-02, respectively!. The spectralcharacteristics of the laser and luminescence output weremeasured with an Optical Multichannel Analyzer ~PrincetonInstruments!. In the case of the tuning range measurements aquartz prism was incorporated between the rear mirror andthe dye cell as a dispersive element. Wavelength tuning wasachieved by rotation of the rear mirror.The lasing performance of TOP-PPV was studied inthree solvents; tetrahydofuran, hexane, and p-xylene ~Merck,spectroscopic grade!. In the case of hexane ~a poor solventfor TOP-PPV! the solution was filtered over an 0.2 mm filterto remove undissolved compound. The reference laser dyesFIG. 1. Absorbance and emission spectra of the TOP-PPV copolymer inhexane. Inset ~top right-hand side!: the chemical structure of the TOP-PPVrepeat unit./95/66(25)/3404/3/$6.00 © 1995 American Institute of Physicsbject¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspCoumarin 120 and 47 ~Lambdachrome LC 4400 and LC4700! were used in ethanol solution ~Merck, spectroscopicgrade!. All prepared solutions had a transmittance of 1% atl5355 nm, measured in a standard 10 mm quartz cuvette ona SLM aminco 3000 diode array spectrometer. Concentrationdependent measurements at fixed pump energy indicated thatthe transmittance ~T51%! of the dye solutions were in theregion of optimum efficiency.Clear evidence of laser action of the TOP-PPV copoly-mer is shown in Fig. 3. When the pump energy exceeds thethreshold energy of lasing, intense blue light with a narrowspectral bandwidth @7 nm, full width at half-maximum~FWHM!# was emerging from the output coupler. The spec-trum of the spontaneous emission was obtained after block-ing the rear mirror of the cavity to interrupt the feedbacksystem. The wavelength of laser generation coincides withthe maximum of the fluorescence emission spectrum.Figure 4 shows the ordinary linear dependence of theoutput pulse energy of the dyes as function of the input pulseenergy of the Nd:YAG laser. This plot clearly demonstratesthat the conversion efficiency ~7%! of TOP-PPV in hexane isFIG. 2. Experimental setup: L, lens; BS, beam splitter; PD, pyroelectricdetector; RM, concave rear mirror; C, flow cell; and OM, dielectric outputmirror.FIG. 3. Spontaneous ~dotted! and stimulated ~solid! emission spectra ofTOP-PPV in hexane as measured with the linear nondispersive cavity.Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subsignificantly higher than in all other cases. The conversionefficiencies and lasing wavelengths for all dyes are given inTable I. The efficiencies of TOP-PPV in THF and p-xylene~1.8% and 2.8%, respectively! are comparable to that of thecoumarin dyes. As expected, the lasing wavelength for TOP-PPV in THF and p-xylene are red shifted ~bathochromicshift! with respect to hexane due to increasing solvent polar-ity. The lasing bandwidth of the TOP-PPV polymer was ap-proximately 7 nm in all solvents. The bandwidth of bothcoumarin dyes was almost twice larger, 12 nm. During allmeasurements no visible signs of photodegradation were ob-served.The results of the wavelength tunability measurementsare shown in Table I. For the TOP-PPV copolymer in hexanethe tuning curve and the fluorescence spectrum are plotted inFig. 5. From this plot it can be seen that the tuning curvefollows the shape of the emission spectrum in the wave-length region with the highest emission cross section ~414–452 nm!, due to the small overlap between absorbance andemission band. The wavelength tuning range of TOP-PPV inhexane Dl538 nm! was the highest among all dye/solventsystems measured, which demonstrated the superior effi-ciency of this polymer solution. It should be mentioned thatthe bandwidth of laser generation was 3 nm ~FWHM! in allFIG. 4. Plot of the output pulse energy of the dye laser as funciton of theinput pulse energy of the Nd:YAG pump beam in case of m, TOP-PPVcopolymer in hexane; h, TOP-PPV copolymer in p-xylene; and d, Cou-marin 120 in ethanol. The slope of the lines represents the energy conver-sion efficiency.TABLE I. Comparison of the laser characteristics of Coumarin 47, 120, andTOP-PPV.Dye Solventl lasa~nm!Efficiencya~%!Tuning rangeb~nm!TOP-PPV THF 449 1.8 438–456p-xylene 449 2.8 436–456hexane 440 6.8 414–452Coumarin 47 ethanol 451 2.8 444–470Coumarin 120 ethanol 439 2.3 424–450aLinear nondispersive cavity.bDispersive cavity.3405Brouwer et al.ject¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspcases and was mainly determined by the dispersion of thecavity.The reason for the higher conversion efficiency of TOP-PPV in hexane is unclear at this moment. Gel permeationchromatography ~GPC! of the solution revealed that the mo-lecular weight distribution changed with respect to THF andp-xylene. Due to the poor solubility in hexane, only thelower molecular weight species dissolved and as a result theFIG. 5. Tuning curve ~-j-! and luminescence spectrum ~dashed! of theTOP-PPV copolymer in hexane ~pump energy 10 mJ!.3406 Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subpolydispersity (Mw /Mn) decreased from 1.7 ~in THF! to1.17 (Mn53.13103, Mw53.63103).In conclusion, we have demonstrated the performance ofa novel high efficiency copolymer laser dye in the bluewavelength region. The conversion efficiency when pumpedby third harmonic radiation of a Nd:YAG laser exceeds thatof the well-known coumarin dyes in this wavelength region.In the case of the TOP-PPV copolymer in hexane a wave-length tuning range of almost 40 nm was obtained. The las-ing performance of this polymer shows considerable promisefor the development of stable solid-state dye doped laser ma-terials based on TOP-PPV. This research was financially sup-ported by SON/STW and by the EEC ~Human Captial andMobility program!.1 J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Nature ~London!347, 539 ~1990!.2D. Braun and A. J. Heeger, Appl. Phys. Lett. 58, 1982 ~1991!.3N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, and A. B.Holmes, Nature ~London! 365, 628 ~1993!.4G. G. Malliaras, J. K. Herrema, J. Wildeman, R. H. Wieringa, R. E. Gill,S. S. Lampoura, and G. Hadziioannou, Adv. Mater. 5, 721 ~1993!.5R. E. Gill, G. G. Malliaras, J. Wildeman, and G. Hadziioannou, Adv.Mater. 6, 132 ~1994!.6D. Moses, Appl. Phys. Lett. 60, 3215 ~1992!.7D. Moses, U. S. Patent No. 5,237,582 A ~1992!.8A. Hilberer, J. Wildeman, B. J. van der Scheer, and G. Hadziioannou,Macromolecules 28, No. 13 ~1995!.Brouwer et al.ject¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jsp

The lasing performance and wavelength tunability of a novel high efficiency copolymer poly[(2, 5, 2‘, 5‘‐tetraoctyl)‐p‐terphenyl‐4,4‘‐ylene vinylene‐p‐phenylene vinylene], TOP‐PPV, pumped with third harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The results were compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimental conditions. The efficiency of the TOP‐PPV copolymer in hexane exceeds that of both coumarin dyes with more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelength region between 414 and 456 nm (Δλ=38 nm)

Proceedings - University of Groningen

   University of GroningenNovel high efficiency copolymer laser dye in the blue wavelength regionBrouwer, H. J.; Krasnikov, V. V.; Hilberer, A.; Wildeman, J.; Hadziioannou, G.Published in:Applied Physics LettersDOI:10.1063/1.113368IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Brouwer, H. J., Krasnikov, V. V., Hilberer, A., Wildeman, J., & Hadziioannou, G. (1995). Novel highefficiency copolymer laser dye in the blue wavelength region. Applied Physics Letters, 66(25), 3404-3406.https://doi.org/10.1063/1.113368CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 16-07-2023Novel high efficiency copolymer laser dye in the blue wavelength regionHendrik-Jan Brouwer, Victor V. Krasnikov, Alain Hilberer, Jurjen Wildeman,and George HadziioannouPolymer Chemistry Department, Material Science Centre, State University Groningen, Nyenborgh 4,9747 AG Groningen, The Netherlands~Received 30 November 1994; accepted for publication 21 April 1995!The lasing performance and wavelength tunability of a novel high efficiency copolymer poly@~2, 5,29, 59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#, TOP-PPV, pumped withthird harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The resultswere compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimentalconditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyeswith more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelengthregion between 414 and 456 nm~Dl538 nm!. © 1995 American Institute of Physics.er,he.wasaseres andwasinyesr inIn 1990, research in the field of semiconducting congated polymers led to the introduction of the first polymlight emitting diodes based on poly@p-phenylene vinylene#.1,2This observation of electroluminescence triggered intensresearch by numerous groups and resulted in the elaboraof various other semiconducting polymer light emitting dode ~LED! devices with impressive efficiency3 and colortunability.4,5 It was realized that the high photoluminescenquantum yield of conjugated polymers made them promiscandidates for active laser media in the liquid or solid staFurthermore, due to their good processability and mechcal properties, polymeric dyes have a potential advantagactive gain media in dye doped polymeric optical devicLaser action of a semiconducting polymer~MEH-PPV! inthe liquid state6,7 operating in the yellow/red wavelength region was achieved for the first time in 1992. The reportlasing performance of this polymer was comparable to tof the most efficient laser dye Rhodamine 6G.In this letter we demonstrate for the first time the lasiperformance of a novel highly efficient copolymepoly@~2,5,29,59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#,8 TOP-PPV, in the blue wavelengthregion. In Fig. 1~inset top right! the structure of the repeaunit is given. The TOP-PPV copolymer~Mn52.63103, Mw54.53103) has a well-defined conjugatebackbone, consisting of regularly alternating terphenyle~TOP! andp-phenylene-vinylene~PPV! blocks. The presenceof four octyl side chains provides solubility of the conjugatform in common polar solvents such as tetrahydrofur~THF! and chloroform. The polymer exhibits a high thermstability, up to 420 °C under nitrogen. Figure 1 shows tabsorbance ~lmax5357 nm! and emission (lmax5440 nm) spectra of a solution of the TOP-PPV copolymin hexane~10 mm quartz cell!. Photoluminescence quantumyields as high asMF;0.8–0.9 were obtained in solution8~THF, hexane! which gave a clear indication of the possibiity of lasing action.The energy conversion efficiency measurements wperformed using a linear nondispersive cavity in a quasilgitudinal pumping arrangement. The experimental setupschematically depicted in Fig. 2. The cavity is defined byconcave metallic rear mirror and a flat dielectric output co3404 Appl. Phys. Lett. 66 (25), 19 June 1995 0003-6951Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjeju-erivetioni-ceingte.ani-e ases.-edhatngrtdneedanalheerl-ereon-isau-pler ~transmittanceT581%,l5360–460 nm! separated by adistance of 95 mm. The pump source was a Nd:YAG lasQuanta-Ray GCR 130-50, operating at tripled frequency~l5355 nm,p-polarized, pulse width58 ns! with a repetitionrate of 1 Hz. In order to prevent laser generation from tcell walls and to minimize Fresnel losses, the dye cell~pathlength 10 mm! was tilted with respect to the pumping beamThe angle between the pumping and generated beamapproximately 7°. The input and output pulse energy wmonitored with two calibrated pyroelectric detectors~Coher-ent LMP 5, Molectron J3-02, respectively!. The spectralcharacteristics of the laser and luminescence output wmeasured with an Optical Multichannel Analyzer~PrincetonInstruments!. In the case of the tuning range measurementquartz prism was incorporated between the rear mirror athe dye cell as a dispersive element. Wavelength tuningachieved by rotation of the rear mirror.The lasing performance of TOP-PPV was studiedthree solvents; tetrahydofuran, hexane, andp-xylene~Merck,spectroscopic grade!. In the case of hexane~a poor solventfor TOP-PPV! the solution was filtered over an 0.2mm filterto remove undissolved compound. The reference laser dFIG. 1. Absorbance and emission spectra of the TOP-PPV copolymehexane. Inset~top right-hand side!: the chemical structure of the TOP-PPVrepeat unit./95/66(25)/3404/3/$6.00 © 1995 American Institute of Physicsct¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspnn-r--lb-sein-dnfi-ter-dCoumarin 120 and 47~Lambdachrome LC 4400 and LC4700! were used in ethanol solution~Merck, spectroscopicgrade!. All prepared solutions had a transmittance of 1%l5355 nm, measured in a standard 10 mm quartz cuvettea SLM aminco 3000 diode array spectrometer. Concentratdependent measurements at fixed pump energy indicatedthe transmittance~T51%! of the dye solutions were in theregion of optimum efficiency.Clear evidence of laser action of the TOP-PPV copolmer is shown in Fig. 3. When the pump energy exceedsthreshold energy of lasing, intense blue light with a narrospectral bandwidth@7 nm, full width at half-maximum~FWHM!# was emerging from the output coupler. The spetrum of the spontaneous emission was obtained after bloing the rear mirror of the cavity to interrupt the feedbacsystem. The wavelength of laser generation coincides wthe maximum of the fluorescence emission spectrum.Figure 4 shows the ordinary linear dependence of toutput pulse energy of the dyes as function of the input puenergy of the Nd:YAG laser. This plot clearly demonstratthat the conversion efficiency~7%! of TOP-PPV in hexane isFIG. 2. Experimental setup: L, lens; BS, beam splitter; PD, pyroelectdetector; RM, concave rear mirror; C, flow cell; and OM, dielectric outpmirror.FIG. 3. Spontaneous~dotted! and stimulated~solid! emission spectra ofTOP-PPV in hexane as measured with the linear nondispersive cavity.Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecatonionthaty-thewc-ck-kithhelseessignificantly higher than in all other cases. The conversioefficiencies and lasing wavelengths for all dyes are given iTable I. The efficiencies of TOP-PPV in THF andp-xylene~1.8% and 2.8%, respectively! are comparable to that of thecoumarin dyes. As expected, the lasing wavelength for TOPPPV in THF andp-xylene are red shifted~bathochromicshift! with respect to hexane due to increasing solvent polaity. The lasing bandwidth of the TOP-PPV polymer was approximately 7 nm in all solvents. The bandwidth of bothcoumarin dyes was almost twice larger, 12 nm. During almeasurements no visible signs of photodegradation were oserved.The results of the wavelength tunability measurementare shown in Table I. For the TOP-PPV copolymer in hexanthe tuning curve and the fluorescence spectrum are plottedFig. 5. From this plot it can be seen that the tuning curvefollows the shape of the emission spectrum in the wavelength region with the highest emission cross section~414–452 nm!, due to the small overlap between absorbance anemission band. The wavelength tuning range of TOP-PPV ihexaneDl538 nm! was the highest among all dye/solventsystems measured, which demonstrated the superior efciency of this polymer solution. It should be mentioned thathe bandwidth of laser generation was 3 nm~FWHM! in allricutFIG. 4. Plot of the output pulse energy of the dye laser as funciton of thinput pulse energy of the Nd:YAG pump beam in case ofm, TOP-PPVcopolymer in hexane;h, TOP-PPV copolymer inp-xylene; andd, Cou-marin 120 in ethanol. The slope of the lines represents the energy convesion efficiency.TABLE I. Comparison of the laser characteristics of Coumarin 47, 120, anTOP-PPV.Dye Solventl lasa~nm!Efficiencya~%!Tuning rangeb~nm!TOP-PPV THF 449 1.8 438–456p-xylene 449 2.8 436–456hexane 440 6.8 414–452Coumarin 47 ethanol 451 2.8 444–470Coumarin 120 ethanol 439 2.3 424–450aLinear nondispersive cavity.bDispersive cavity.3405Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspf--e--,cases and was mainly determined by the dispersion ofcavity.The reason for the higher conversion efficiency of TOPPPV in hexane is unclear at this moment. Gel permeatichromatography~GPC! of the solution revealed that the mo-lecular weight distribution changed with respect to THF anp-xylene. Due to the poor solubility in hexane, only thlower molecular weight species dissolved and as a resultFIG. 5. Tuning curve~-j-! and luminescence spectrum~dashed! of theTOP-PPV copolymer in hexane~pump energy 10 mJ!.3406 Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecthe-ondethepolydispersity (Mw /Mn) decreased from 1.7~in THF! to1.17 (Mn53.13103, Mw53.63103).In conclusion, we have demonstrated the performance oa novel high efficiency copolymer laser dye in the bluewavelength region. The conversion efficiency when pumpedby third harmonic radiation of a Nd:YAG laser exceeds thatof the well-known coumarin dyes in this wavelength region.In the case of the TOP-PPV copolymer in hexane a wavelength tuning range of almost 40 nm was obtained. The lasing performance of this polymer shows considerable promisfor the development of stable solid-state dye doped laser materials based on TOP-PPV. This research was financially supported by SON/STW and by the EEC~Human Captial andMobility program!.1J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Nature~London!347, 539 ~1990!.2D. Braun and A. J. Heeger, Appl. Phys. Lett.58, 1982~1991!.3N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, and A. B.Holmes, Nature~London! 365, 628 ~1993!.4G. G. Malliaras, J. K. Herrema, J. Wildeman, R. H. Wieringa, R. E. Gill,S. S. Lampoura, and G. Hadziioannou, Adv. Mater.5, 721 ~1993!.5R. E. Gill, G. G. Malliaras, J. Wildeman, and G. Hadziioannou, Adv.Mater.6, 132 ~1994!.6D. Moses, Appl. Phys. Lett.60, 3215~1992!.7D. Moses, U. S. Patent No. 5,237,582 A~1992!.8A. Hilberer, J. Wildeman, B. J. van der Scheer, and G. HadziioannouMacromolecules28, No. 13 ~1995!.Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jsp

   University of GroningenNovel high efficiency copolymer laser dye in the blue wavelength regionBrouwer, H. J.; Krasnikov, V. V.; Hilberer, A.; Wildeman, J.; Hadziioannou, G.Published in:Applied Physics LettersDOI:10.1063/1.113368IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Brouwer, H. J., Krasnikov, V. V., Hilberer, A., Wildeman, J., & Hadziioannou, G. (1995). Novel highefficiency copolymer laser dye in the blue wavelength region. Applied Physics Letters, 66(25), 3404-3406.https://doi.org/10.1063/1.113368CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-09-2023Novel high efficiency copolymer laser dye in the blue wavelength regionHendrik-Jan Brouwer, Victor V. Krasnikov, Alain Hilberer, Jurjen Wildeman,and George HadziioannouPolymer Chemistry Department, Material Science Centre, State University Groningen, Nyenborgh 4,9747 AG Groningen, The Netherlands~Received 30 November 1994; accepted for publication 21 April 1995!The lasing performance and wavelength tunability of a novel high efficiency copolymer poly@~2, 5,29, 59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#, TOP-PPV, pumped withthird harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The resultswere compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimentalconditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyeswith more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelengthregion between 414 and 456 nm~Dl538 nm!. © 1995 American Institute of Physics.er,he.wasaseres andwasinyesr inIn 1990, research in the field of semiconducting congated polymers led to the introduction of the first polymlight emitting diodes based on poly@p-phenylene vinylene#.1,2This observation of electroluminescence triggered intensresearch by numerous groups and resulted in the elaboraof various other semiconducting polymer light emitting dode ~LED! devices with impressive efficiency3 and colortunability.4,5 It was realized that the high photoluminescenquantum yield of conjugated polymers made them promiscandidates for active laser media in the liquid or solid staFurthermore, due to their good processability and mechcal properties, polymeric dyes have a potential advantagactive gain media in dye doped polymeric optical devicLaser action of a semiconducting polymer~MEH-PPV! inthe liquid state6,7 operating in the yellow/red wavelength region was achieved for the first time in 1992. The reportlasing performance of this polymer was comparable to tof the most efficient laser dye Rhodamine 6G.In this letter we demonstrate for the first time the lasiperformance of a novel highly efficient copolymepoly@~2,5,29,59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#,8 TOP-PPV, in the blue wavelengthregion. In Fig. 1~inset top right! the structure of the repeaunit is given. The TOP-PPV copolymer~Mn52.63103, Mw54.53103) has a well-defined conjugatebackbone, consisting of regularly alternating terphenyle~TOP! andp-phenylene-vinylene~PPV! blocks. The presenceof four octyl side chains provides solubility of the conjugatform in common polar solvents such as tetrahydrofur~THF! and chloroform. The polymer exhibits a high thermstability, up to 420 °C under nitrogen. Figure 1 shows tabsorbance ~lmax5357 nm! and emission (lmax5440 nm) spectra of a solution of the TOP-PPV copolymin hexane~10 mm quartz cell!. Photoluminescence quantumyields as high asMF;0.8–0.9 were obtained in solution8~THF, hexane! which gave a clear indication of the possibiity of lasing action.The energy conversion efficiency measurements wperformed using a linear nondispersive cavity in a quasilgitudinal pumping arrangement. The experimental setupschematically depicted in Fig. 2. The cavity is defined byconcave metallic rear mirror and a flat dielectric output co3404 Appl. Phys. Lett. 66 (25), 19 June 1995 0003-6951Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjeju-erivetioni-ceingte.ani-e ases.-edhatngrtdneedanalheerl-ereon-isau-pler ~transmittanceT581%,l5360–460 nm! separated by adistance of 95 mm. The pump source was a Nd:YAG lasQuanta-Ray GCR 130-50, operating at tripled frequency~l5355 nm,p-polarized, pulse width58 ns! with a repetitionrate of 1 Hz. In order to prevent laser generation from tcell walls and to minimize Fresnel losses, the dye cell~pathlength 10 mm! was tilted with respect to the pumping beamThe angle between the pumping and generated beamapproximately 7°. The input and output pulse energy wmonitored with two calibrated pyroelectric detectors~Coher-ent LMP 5, Molectron J3-02, respectively!. The spectralcharacteristics of the laser and luminescence output wmeasured with an Optical Multichannel Analyzer~PrincetonInstruments!. In the case of the tuning range measurementquartz prism was incorporated between the rear mirror athe dye cell as a dispersive element. Wavelength tuningachieved by rotation of the rear mirror.The lasing performance of TOP-PPV was studiedthree solvents; tetrahydofuran, hexane, andp-xylene~Merck,spectroscopic grade!. In the case of hexane~a poor solventfor TOP-PPV! the solution was filtered over an 0.2mm filterto remove undissolved compound. The reference laser dFIG. 1. Absorbance and emission spectra of the TOP-PPV copolymehexane. Inset~top right-hand side!: the chemical structure of the TOP-PPVrepeat unit./95/66(25)/3404/3/$6.00 © 1995 American Institute of Physicsct¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspnn-r--lb-sein-dnfi-ter-dCoumarin 120 and 47~Lambdachrome LC 4400 and LC4700! were used in ethanol solution~Merck, spectroscopicgrade!. All prepared solutions had a transmittance of 1%l5355 nm, measured in a standard 10 mm quartz cuvettea SLM aminco 3000 diode array spectrometer. Concentratdependent measurements at fixed pump energy indicatedthe transmittance~T51%! of the dye solutions were in theregion of optimum efficiency.Clear evidence of laser action of the TOP-PPV copolmer is shown in Fig. 3. When the pump energy exceedsthreshold energy of lasing, intense blue light with a narrospectral bandwidth@7 nm, full width at half-maximum~FWHM!# was emerging from the output coupler. The spetrum of the spontaneous emission was obtained after bloing the rear mirror of the cavity to interrupt the feedbacsystem. The wavelength of laser generation coincides wthe maximum of the fluorescence emission spectrum.Figure 4 shows the ordinary linear dependence of toutput pulse energy of the dyes as function of the input puenergy of the Nd:YAG laser. This plot clearly demonstratthat the conversion efficiency~7%! of TOP-PPV in hexane isFIG. 2. Experimental setup: L, lens; BS, beam splitter; PD, pyroelectdetector; RM, concave rear mirror; C, flow cell; and OM, dielectric outpmirror.FIG. 3. Spontaneous~dotted! and stimulated~solid! emission spectra ofTOP-PPV in hexane as measured with the linear nondispersive cavity.Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecatonionthaty-thewc-ck-kithhelseessignificantly higher than in all other cases. The conversioefficiencies and lasing wavelengths for all dyes are given iTable I. The efficiencies of TOP-PPV in THF andp-xylene~1.8% and 2.8%, respectively! are comparable to that of thecoumarin dyes. As expected, the lasing wavelength for TOPPPV in THF andp-xylene are red shifted~bathochromicshift! with respect to hexane due to increasing solvent polaity. The lasing bandwidth of the TOP-PPV polymer was approximately 7 nm in all solvents. The bandwidth of bothcoumarin dyes was almost twice larger, 12 nm. During almeasurements no visible signs of photodegradation were oserved.The results of the wavelength tunability measurementare shown in Table I. For the TOP-PPV copolymer in hexanthe tuning curve and the fluorescence spectrum are plottedFig. 5. From this plot it can be seen that the tuning curvefollows the shape of the emission spectrum in the wavelength region with the highest emission cross section~414–452 nm!, due to the small overlap between absorbance anemission band. The wavelength tuning range of TOP-PPV ihexaneDl538 nm! was the highest among all dye/solventsystems measured, which demonstrated the superior efciency of this polymer solution. It should be mentioned thathe bandwidth of laser generation was 3 nm~FWHM! in allricutFIG. 4. Plot of the output pulse energy of the dye laser as funciton of thinput pulse energy of the Nd:YAG pump beam in case ofm, TOP-PPVcopolymer in hexane;h, TOP-PPV copolymer inp-xylene; andd, Cou-marin 120 in ethanol. The slope of the lines represents the energy convesion efficiency.TABLE I. Comparison of the laser characteristics of Coumarin 47, 120, anTOP-PPV.Dye Solventl lasa~nm!Efficiencya~%!Tuning rangeb~nm!TOP-PPV THF 449 1.8 438–456p-xylene 449 2.8 436–456hexane 440 6.8 414–452Coumarin 47 ethanol 451 2.8 444–470Coumarin 120 ethanol 439 2.3 424–450aLinear nondispersive cavity.bDispersive cavity.3405Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspf--e--,cases and was mainly determined by the dispersion ofcavity.The reason for the higher conversion efficiency of TOPPPV in hexane is unclear at this moment. Gel permeatichromatography~GPC! of the solution revealed that the mo-lecular weight distribution changed with respect to THF anp-xylene. Due to the poor solubility in hexane, only thlower molecular weight species dissolved and as a resultFIG. 5. Tuning curve~-j-! and luminescence spectrum~dashed! of theTOP-PPV copolymer in hexane~pump energy 10 mJ!.3406 Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecthe-ondethepolydispersity (Mw /Mn) decreased from 1.7~in THF! to1.17 (Mn53.13103, Mw53.63103).In conclusion, we have demonstrated the performance oa novel high efficiency copolymer laser dye in the bluewavelength region. The conversion efficiency when pumpedby third harmonic radiation of a Nd:YAG laser exceeds thatof the well-known coumarin dyes in this wavelength region.In the case of the TOP-PPV copolymer in hexane a wavelength tuning range of almost 40 nm was obtained. The lasing performance of this polymer shows considerable promisfor the development of stable solid-state dye doped laser materials based on TOP-PPV. This research was financially supported by SON/STW and by the EEC~Human Captial andMobility program!.1J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Nature~London!347, 539 ~1990!.2D. Braun and A. J. Heeger, Appl. Phys. Lett.58, 1982~1991!.3N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, and A. B.Holmes, Nature~London! 365, 628 ~1993!.4G. G. Malliaras, J. K. Herrema, J. Wildeman, R. H. Wieringa, R. E. Gill,S. S. Lampoura, and G. Hadziioannou, Adv. Mater.5, 721 ~1993!.5R. E. Gill, G. G. Malliaras, J. Wildeman, and G. Hadziioannou, Adv.Mater.6, 132 ~1994!.6D. Moses, Appl. Phys. Lett.60, 3215~1992!.7D. Moses, U. S. Patent No. 5,237,582 A~1992!.8A. Hilberer, J. Wildeman, B. J. van der Scheer, and G. HadziioannouMacromolecules28, No. 13 ~1995!.Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jsp

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   University of GroningenNovel high efficiency copolymer laser dye in the blue wavelength regionBrouwer, H. J.; Krasnikov, V. V.; Hilberer, A.; Wildeman, J.; Hadziioannou, G.Published in:Applied Physics LettersDOI:10.1063/1.113368IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Brouwer, H. J., Krasnikov, V. V., Hilberer, A., Wildeman, J., & Hadziioannou, G. (1995). Novel highefficiency copolymer laser dye in the blue wavelength region. Applied Physics Letters, 66(25), 3404-3406.https://doi.org/10.1063/1.113368CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 13-02-2023Novel high efficiency copolymer laser dye in the blue wavelength regionHendrik-Jan Brouwer, Victor V. Krasnikov, Alain Hilberer, Jurjen Wildeman,and George HadziioannouPolymer Chemistry Department, Material Science Centre, State University Groningen, Nyenborgh 4,9747 AG Groningen, The Netherlands~Received 30 November 1994; accepted for publication 21 April 1995!The lasing performance and wavelength tunability of a novel high efficiency copolymer poly@~2, 5,29, 59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#, TOP-PPV, pumped withthird harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The resultswere compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimentalconditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyeswith more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelengthregion between 414 and 456 nm~Dl538 nm!. © 1995 American Institute of Physics.er,he.wasaseres andwasinyesr inIn 1990, research in the field of semiconducting congated polymers led to the introduction of the first polymlight emitting diodes based on poly@p-phenylene vinylene#.1,2This observation of electroluminescence triggered intensresearch by numerous groups and resulted in the elaboraof various other semiconducting polymer light emitting dode ~LED! devices with impressive efficiency3 and colortunability.4,5 It was realized that the high photoluminescenquantum yield of conjugated polymers made them promiscandidates for active laser media in the liquid or solid staFurthermore, due to their good processability and mechcal properties, polymeric dyes have a potential advantagactive gain media in dye doped polymeric optical devicLaser action of a semiconducting polymer~MEH-PPV! inthe liquid state6,7 operating in the yellow/red wavelength region was achieved for the first time in 1992. The reportlasing performance of this polymer was comparable to tof the most efficient laser dye Rhodamine 6G.In this letter we demonstrate for the first time the lasiperformance of a novel highly efficient copolymepoly@~2,5,29,59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#,8 TOP-PPV, in the blue wavelengthregion. In Fig. 1~inset top right! the structure of the repeaunit is given. The TOP-PPV copolymer~Mn52.63103, Mw54.53103) has a well-defined conjugatebackbone, consisting of regularly alternating terphenyle~TOP! andp-phenylene-vinylene~PPV! blocks. The presenceof four octyl side chains provides solubility of the conjugatform in common polar solvents such as tetrahydrofur~THF! and chloroform. The polymer exhibits a high thermstability, up to 420 °C under nitrogen. Figure 1 shows tabsorbance ~lmax5357 nm! and emission (lmax5440 nm) spectra of a solution of the TOP-PPV copolymin hexane~10 mm quartz cell!. Photoluminescence quantumyields as high asMF;0.8–0.9 were obtained in solution8~THF, hexane! which gave a clear indication of the possibiity of lasing action.The energy conversion efficiency measurements wperformed using a linear nondispersive cavity in a quasilgitudinal pumping arrangement. The experimental setupschematically depicted in Fig. 2. The cavity is defined byconcave metallic rear mirror and a flat dielectric output co3404 Appl. Phys. Lett. 66 (25), 19 June 1995 0003-6951Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjeju-erivetioni-ceingte.ani-e ases.-edhatngrtdneedanalheerl-ereon-isau-pler ~transmittanceT581%,l5360–460 nm! separated by adistance of 95 mm. The pump source was a Nd:YAG lasQuanta-Ray GCR 130-50, operating at tripled frequency~l5355 nm,p-polarized, pulse width58 ns! with a repetitionrate of 1 Hz. In order to prevent laser generation from tcell walls and to minimize Fresnel losses, the dye cell~pathlength 10 mm! was tilted with respect to the pumping beamThe angle between the pumping and generated beamapproximately 7°. The input and output pulse energy wmonitored with two calibrated pyroelectric detectors~Coher-ent LMP 5, Molectron J3-02, respectively!. The spectralcharacteristics of the laser and luminescence output wmeasured with an Optical Multichannel Analyzer~PrincetonInstruments!. In the case of the tuning range measurementquartz prism was incorporated between the rear mirror athe dye cell as a dispersive element. Wavelength tuningachieved by rotation of the rear mirror.The lasing performance of TOP-PPV was studiedthree solvents; tetrahydofuran, hexane, andp-xylene~Merck,spectroscopic grade!. In the case of hexane~a poor solventfor TOP-PPV! the solution was filtered over an 0.2mm filterto remove undissolved compound. The reference laser dFIG. 1. Absorbance and emission spectra of the TOP-PPV copolymehexane. Inset~top right-hand side!: the chemical structure of the TOP-PPVrepeat unit./95/66(25)/3404/3/$6.00 © 1995 American Institute of Physicsct¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspnn-r--lb-sein-dnfi-ter-dCoumarin 120 and 47~Lambdachrome LC 4400 and LC4700! were used in ethanol solution~Merck, spectroscopicgrade!. All prepared solutions had a transmittance of 1%l5355 nm, measured in a standard 10 mm quartz cuvettea SLM aminco 3000 diode array spectrometer. Concentratdependent measurements at fixed pump energy indicatedthe transmittance~T51%! of the dye solutions were in theregion of optimum efficiency.Clear evidence of laser action of the TOP-PPV copolmer is shown in Fig. 3. When the pump energy exceedsthreshold energy of lasing, intense blue light with a narrospectral bandwidth@7 nm, full width at half-maximum~FWHM!# was emerging from the output coupler. The spetrum of the spontaneous emission was obtained after bloing the rear mirror of the cavity to interrupt the feedbacsystem. The wavelength of laser generation coincides wthe maximum of the fluorescence emission spectrum.Figure 4 shows the ordinary linear dependence of toutput pulse energy of the dyes as function of the input puenergy of the Nd:YAG laser. This plot clearly demonstratthat the conversion efficiency~7%! of TOP-PPV in hexane isFIG. 2. Experimental setup: L, lens; BS, beam splitter; PD, pyroelectdetector; RM, concave rear mirror; C, flow cell; and OM, dielectric outpmirror.FIG. 3. Spontaneous~dotted! and stimulated~solid! emission spectra ofTOP-PPV in hexane as measured with the linear nondispersive cavity.Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecatonionthaty-thewc-ck-kithhelseessignificantly higher than in all other cases. The conversioefficiencies and lasing wavelengths for all dyes are given iTable I. The efficiencies of TOP-PPV in THF andp-xylene~1.8% and 2.8%, respectively! are comparable to that of thecoumarin dyes. As expected, the lasing wavelength for TOPPPV in THF andp-xylene are red shifted~bathochromicshift! with respect to hexane due to increasing solvent polaity. The lasing bandwidth of the TOP-PPV polymer was approximately 7 nm in all solvents. The bandwidth of bothcoumarin dyes was almost twice larger, 12 nm. During almeasurements no visible signs of photodegradation were oserved.The results of the wavelength tunability measurementare shown in Table I. For the TOP-PPV copolymer in hexanthe tuning curve and the fluorescence spectrum are plottedFig. 5. From this plot it can be seen that the tuning curvefollows the shape of the emission spectrum in the wavelength region with the highest emission cross section~414–452 nm!, due to the small overlap between absorbance anemission band. The wavelength tuning range of TOP-PPV ihexaneDl538 nm! was the highest among all dye/solventsystems measured, which demonstrated the superior efciency of this polymer solution. It should be mentioned thathe bandwidth of laser generation was 3 nm~FWHM! in allricutFIG. 4. Plot of the output pulse energy of the dye laser as funciton of thinput pulse energy of the Nd:YAG pump beam in case ofm, TOP-PPVcopolymer in hexane;h, TOP-PPV copolymer inp-xylene; andd, Cou-marin 120 in ethanol. The slope of the lines represents the energy convesion efficiency.TABLE I. Comparison of the laser characteristics of Coumarin 47, 120, anTOP-PPV.Dye Solventl lasa~nm!Efficiencya~%!Tuning rangeb~nm!TOP-PPV THF 449 1.8 438–456p-xylene 449 2.8 436–456hexane 440 6.8 414–452Coumarin 47 ethanol 451 2.8 444–470Coumarin 120 ethanol 439 2.3 424–450aLinear nondispersive cavity.bDispersive cavity.3405Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspf--e--,cases and was mainly determined by the dispersion ofcavity.The reason for the higher conversion efficiency of TOPPPV in hexane is unclear at this moment. Gel permeatichromatography~GPC! of the solution revealed that the mo-lecular weight distribution changed with respect to THF anp-xylene. Due to the poor solubility in hexane, only thlower molecular weight species dissolved and as a resultFIG. 5. Tuning curve~-j-! and luminescence spectrum~dashed! of theTOP-PPV copolymer in hexane~pump energy 10 mJ!.3406 Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecthe-ondethepolydispersity (Mw /Mn) decreased from 1.7~in THF! to1.17 (Mn53.13103, Mw53.63103).In conclusion, we have demonstrated the performance oa novel high efficiency copolymer laser dye in the bluewavelength region. The conversion efficiency when pumpedby third harmonic radiation of a Nd:YAG laser exceeds thatof the well-known coumarin dyes in this wavelength region.In the case of the TOP-PPV copolymer in hexane a wavelength tuning range of almost 40 nm was obtained. The lasing performance of this polymer shows considerable promisfor the development of stable solid-state dye doped laser materials based on TOP-PPV. This research was financially supported by SON/STW and by the EEC~Human Captial andMobility program!.1J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Nature~London!347, 539 ~1990!.2D. Braun and A. J. Heeger, Appl. Phys. Lett.58, 1982~1991!.3N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, and A. B.Holmes, Nature~London! 365, 628 ~1993!.4G. G. Malliaras, J. K. Herrema, J. Wildeman, R. H. Wieringa, R. E. Gill,S. S. Lampoura, and G. Hadziioannou, Adv. Mater.5, 721 ~1993!.5R. E. Gill, G. G. Malliaras, J. Wildeman, and G. Hadziioannou, Adv.Mater.6, 132 ~1994!.6D. Moses, Appl. Phys. Lett.60, 3215~1992!.7D. Moses, U. S. Patent No. 5,237,582 A~1992!.8A. Hilberer, J. Wildeman, B. J. van der Scheer, and G. HadziioannouMacromolecules28, No. 13 ~1995!.Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jsp

   University of GroningenNovel high efficiency copolymer laser dye in the blue wavelength regionBrouwer, H. J.; Krasnikov, V. V.; Hilberer, A.; Wildeman, J.; Hadziioannou, G.Published in:Applied Physics LettersDOI:10.1063/1.113368IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Brouwer, H. J., Krasnikov, V. V., Hilberer, A., Wildeman, J., & Hadziioannou, G. (1995). Novel highefficiency copolymer laser dye in the blue wavelength region. Applied Physics Letters, 66(25), 3404-3406.https://doi.org/10.1063/1.113368CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 10-03-2023Novel high efficiency copolymer laser dye in the blue wavelength regionHendrik-Jan Brouwer, Victor V. Krasnikov, Alain Hilberer, Jurjen Wildeman,and George HadziioannouPolymer Chemistry Department, Material Science Centre, State University Groningen, Nyenborgh 4,9747 AG Groningen, The Netherlands~Received 30 November 1994; accepted for publication 21 April 1995!The lasing performance and wavelength tunability of a novel high efficiency copolymer poly@~2, 5,29, 59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#, TOP-PPV, pumped withthird harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The resultswere compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimentalconditions. The efficiency of the TOP-PPV copolymer in hexane exceeds that of both coumarin dyeswith more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelengthregion between 414 and 456 nm~Dl538 nm!. © 1995 American Institute of Physics.er,he.wasaseres andwasinyesr inIn 1990, research in the field of semiconducting congated polymers led to the introduction of the first polymlight emitting diodes based on poly@p-phenylene vinylene#.1,2This observation of electroluminescence triggered intensresearch by numerous groups and resulted in the elaboraof various other semiconducting polymer light emitting dode ~LED! devices with impressive efficiency3 and colortunability.4,5 It was realized that the high photoluminescenquantum yield of conjugated polymers made them promiscandidates for active laser media in the liquid or solid staFurthermore, due to their good processability and mechcal properties, polymeric dyes have a potential advantagactive gain media in dye doped polymeric optical devicLaser action of a semiconducting polymer~MEH-PPV! inthe liquid state6,7 operating in the yellow/red wavelength region was achieved for the first time in 1992. The reportlasing performance of this polymer was comparable to tof the most efficient laser dye Rhodamine 6G.In this letter we demonstrate for the first time the lasiperformance of a novel highly efficient copolymepoly@~2,5,29,59-tetraoctyl!-p-terphenyl-4,49-ylene vinylene-p-phenylene vinylene#,8 TOP-PPV, in the blue wavelengthregion. In Fig. 1~inset top right! the structure of the repeaunit is given. The TOP-PPV copolymer~Mn52.63103, Mw54.53103) has a well-defined conjugatebackbone, consisting of regularly alternating terphenyle~TOP! andp-phenylene-vinylene~PPV! blocks. The presenceof four octyl side chains provides solubility of the conjugatform in common polar solvents such as tetrahydrofur~THF! and chloroform. The polymer exhibits a high thermstability, up to 420 °C under nitrogen. Figure 1 shows tabsorbance ~lmax5357 nm! and emission (lmax5440 nm) spectra of a solution of the TOP-PPV copolymin hexane~10 mm quartz cell!. Photoluminescence quantumyields as high asMF;0.8–0.9 were obtained in solution8~THF, hexane! which gave a clear indication of the possibiity of lasing action.The energy conversion efficiency measurements wperformed using a linear nondispersive cavity in a quasilgitudinal pumping arrangement. The experimental setupschematically depicted in Fig. 2. The cavity is defined byconcave metallic rear mirror and a flat dielectric output co3404 Appl. Phys. Lett. 66 (25), 19 June 1995 0003-6951Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjeju-erivetioni-ceingte.ani-e ases.-edhatngrtdneedanalheerl-ereon-isau-pler ~transmittanceT581%,l5360–460 nm! separated by adistance of 95 mm. The pump source was a Nd:YAG lasQuanta-Ray GCR 130-50, operating at tripled frequency~l5355 nm,p-polarized, pulse width58 ns! with a repetitionrate of 1 Hz. In order to prevent laser generation from tcell walls and to minimize Fresnel losses, the dye cell~pathlength 10 mm! was tilted with respect to the pumping beamThe angle between the pumping and generated beamapproximately 7°. The input and output pulse energy wmonitored with two calibrated pyroelectric detectors~Coher-ent LMP 5, Molectron J3-02, respectively!. The spectralcharacteristics of the laser and luminescence output wmeasured with an Optical Multichannel Analyzer~PrincetonInstruments!. In the case of the tuning range measurementquartz prism was incorporated between the rear mirror athe dye cell as a dispersive element. Wavelength tuningachieved by rotation of the rear mirror.The lasing performance of TOP-PPV was studiedthree solvents; tetrahydofuran, hexane, andp-xylene~Merck,spectroscopic grade!. In the case of hexane~a poor solventfor TOP-PPV! the solution was filtered over an 0.2mm filterto remove undissolved compound. The reference laser dFIG. 1. Absorbance and emission spectra of the TOP-PPV copolymehexane. Inset~top right-hand side!: the chemical structure of the TOP-PPVrepeat unit./95/66(25)/3404/3/$6.00 © 1995 American Institute of Physicsct¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspnn-r--lb-sein-dnfi-ter-dCoumarin 120 and 47~Lambdachrome LC 4400 and LC4700! were used in ethanol solution~Merck, spectroscopicgrade!. All prepared solutions had a transmittance of 1%l5355 nm, measured in a standard 10 mm quartz cuvettea SLM aminco 3000 diode array spectrometer. Concentratdependent measurements at fixed pump energy indicatedthe transmittance~T51%! of the dye solutions were in theregion of optimum efficiency.Clear evidence of laser action of the TOP-PPV copolmer is shown in Fig. 3. When the pump energy exceedsthreshold energy of lasing, intense blue light with a narrospectral bandwidth@7 nm, full width at half-maximum~FWHM!# was emerging from the output coupler. The spetrum of the spontaneous emission was obtained after bloing the rear mirror of the cavity to interrupt the feedbacsystem. The wavelength of laser generation coincides wthe maximum of the fluorescence emission spectrum.Figure 4 shows the ordinary linear dependence of toutput pulse energy of the dyes as function of the input puenergy of the Nd:YAG laser. This plot clearly demonstratthat the conversion efficiency~7%! of TOP-PPV in hexane isFIG. 2. Experimental setup: L, lens; BS, beam splitter; PD, pyroelectdetector; RM, concave rear mirror; C, flow cell; and OM, dielectric outpmirror.FIG. 3. Spontaneous~dotted! and stimulated~solid! emission spectra ofTOP-PPV in hexane as measured with the linear nondispersive cavity.Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecatonionthaty-thewc-ck-kithhelseessignificantly higher than in all other cases. The conversioefficiencies and lasing wavelengths for all dyes are given iTable I. The efficiencies of TOP-PPV in THF andp-xylene~1.8% and 2.8%, respectively! are comparable to that of thecoumarin dyes. As expected, the lasing wavelength for TOPPPV in THF andp-xylene are red shifted~bathochromicshift! with respect to hexane due to increasing solvent polaity. The lasing bandwidth of the TOP-PPV polymer was approximately 7 nm in all solvents. The bandwidth of bothcoumarin dyes was almost twice larger, 12 nm. During almeasurements no visible signs of photodegradation were oserved.The results of the wavelength tunability measurementare shown in Table I. For the TOP-PPV copolymer in hexanthe tuning curve and the fluorescence spectrum are plottedFig. 5. From this plot it can be seen that the tuning curvefollows the shape of the emission spectrum in the wavelength region with the highest emission cross section~414–452 nm!, due to the small overlap between absorbance anemission band. The wavelength tuning range of TOP-PPV ihexaneDl538 nm! was the highest among all dye/solventsystems measured, which demonstrated the superior efciency of this polymer solution. It should be mentioned thathe bandwidth of laser generation was 3 nm~FWHM! in allricutFIG. 4. Plot of the output pulse energy of the dye laser as funciton of thinput pulse energy of the Nd:YAG pump beam in case ofm, TOP-PPVcopolymer in hexane;h, TOP-PPV copolymer inp-xylene; andd, Cou-marin 120 in ethanol. The slope of the lines represents the energy convesion efficiency.TABLE I. Comparison of the laser characteristics of Coumarin 47, 120, anTOP-PPV.Dye Solventl lasa~nm!Efficiencya~%!Tuning rangeb~nm!TOP-PPV THF 449 1.8 438–456p-xylene 449 2.8 436–456hexane 440 6.8 414–452Coumarin 47 ethanol 451 2.8 444–470Coumarin 120 ethanol 439 2.3 424–450aLinear nondispersive cavity.bDispersive cavity.3405Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jspf--e--,cases and was mainly determined by the dispersion ofcavity.The reason for the higher conversion efficiency of TOPPPV in hexane is unclear at this moment. Gel permeatichromatography~GPC! of the solution revealed that the mo-lecular weight distribution changed with respect to THF anp-xylene. Due to the poor solubility in hexane, only thlower molecular weight species dissolved and as a resultFIG. 5. Tuning curve~-j-! and luminescence spectrum~dashed! of theTOP-PPV copolymer in hexane~pump energy 10 mJ!.3406 Appl. Phys. Lett., Vol. 66, No. 25, 19 June 1995Downloaded¬18¬Dec¬2006¬to¬129.125.25.39.¬Redistribution¬subjecthe-ondethepolydispersity (Mw /Mn) decreased from 1.7~in THF! to1.17 (Mn53.13103, Mw53.63103).In conclusion, we have demonstrated the performance oa novel high efficiency copolymer laser dye in the bluewavelength region. The conversion efficiency when pumpedby third harmonic radiation of a Nd:YAG laser exceeds thatof the well-known coumarin dyes in this wavelength region.In the case of the TOP-PPV copolymer in hexane a wavelength tuning range of almost 40 nm was obtained. The lasing performance of this polymer shows considerable promisfor the development of stable solid-state dye doped laser materials based on TOP-PPV. This research was financially supported by SON/STW and by the EEC~Human Captial andMobility program!.1J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, Nature~London!347, 539 ~1990!.2D. Braun and A. J. Heeger, Appl. Phys. Lett.58, 1982~1991!.3N. C. Greenham, S. C. Moratti, D. D. C. Bradley, R. H. Friend, and A. B.Holmes, Nature~London! 365, 628 ~1993!.4G. G. Malliaras, J. K. Herrema, J. Wildeman, R. H. Wieringa, R. E. Gill,S. S. Lampoura, and G. Hadziioannou, Adv. Mater.5, 721 ~1993!.5R. E. Gill, G. G. Malliaras, J. Wildeman, and G. Hadziioannou, Adv.Mater.6, 132 ~1994!.6D. Moses, Appl. Phys. Lett.60, 3215~1992!.7D. Moses, U. S. Patent No. 5,237,582 A~1992!.8A. Hilberer, J. Wildeman, B. J. van der Scheer, and G. HadziioannouMacromolecules28, No. 13 ~1995!.Brouwer et al.t¬to¬AIP¬license¬or¬copyright,¬see¬http://apl.aip.org/apl/copyright.jsp

Novel high efficiency copolymer laser dye in the blue wavelength region

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