Index and Relief Gratings in Polymer Films for Organic Distributed Feedback Lasers

Kavc, Thomas; Langer, Gregor; Kern, Wolfgang; Kranzelbinder, G.; Toussaere, E.; Turnbull, Graham A.; Samuel, Ifor D. W.; Iskra, Kurt Friedrich; Neger, Theo; Pogantsch, Alexander

doi:10.1021/cm021148f

Cited by 38 publications

(30 citation statements)

References 18 publications

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“…Experiments with interference illumination (k = 266 nm) are now in progress and will be presented in a forthcoming contribution. [24] The application of index and relief gratings in PVBT and PST-co-VBT for optically pumped DFB laser devices will be published elsewhere. [25] …”

Section: Discussionmentioning

confidence: 99%

Formation of Images and Surface Relief Gratings in Photosensitive Polymers Containing SCN Groups

Kavc

Langer

Pölt

et al. 2002

Macromol. Chem. Phys.

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Section: Discussionmentioning

confidence: 99%

Formation of Images and Surface Relief Gratings in Photosensitive Polymers Containing SCN Groups

Kavc

Langer

Pölt

et al. 2002

Macromol. Chem. Phys.

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“…We have previously demonstrated this approach using a variety of porphyrinic molecules, including a ferrocene±porphyrin conjugate bearing a single thiol tether. [9] In this design, the characteristic oxidation potentials of the ferrocene and the porphyrin components are maintained, thereby affording four states (neutral and the three cationic oxidation states from the ferrocene and porphyrin). This approach is limited only by the requirements for synthesis of the covalently linked multiredox molecule.…”

Section: Methodsmentioning

confidence: 99%

“…In these structures the change of the refractive index caused by the UV-induced isomerization of thiocyanate (±SCN) to isothiocyanate (±NCS) groups was employed to provide the required feedback for lasing. [9,10] Using this method, we have shown that two-dimensional gratings of different periods can be easily inscribed, providing limited tunability of the emission wavelength by rotating the substrate. [11] In the present contribution we extend the aforementioned approach by combining the photoreactivity of benzylthiocyanate units with the mechanical properties of a styrene±butadiene rubber (SBR).…”

mentioning

confidence: 99%

“…The origin of the surface-relief pattern is probably some laser ablation during the UV-patterning procedure, as has been described in a previous contribution. [9,11] In this case, an index and a surface-relief grating were superimposed. An atomic force micrograph (AFM) of the patterned surface is presented in Figure 1 (unstretched grating period K 0 = 460 nm, modulation depth of the grating 3 nm).…”

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confidence: 99%

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Continuously Color‐Tunable Rubber Laser

et al. 2004

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Tunable laser emission is a highly desirable feature in modern technologies such as fiber optics for communications. Polymeric materials are interesting candidates for integrated laser devices, due to their mechanical properties and the possibility of low-cost fabrication schemes. It has been shown in the literature that lasers made of organic materials as the gain medium can be realized in a variety of device configurations.[1±3] Possibly the most straightforward approach is inscribing of a distributed feedback (DFB) grating [4,5] into either the substrate or directly into the organic layer. While DFB structures can be easily produced using fabrication methods such as lithography or imprinting techniques, [6] they generally lack the tunability provided by, e.g., an external cavity. Current research is aimed at electrically tunable DFB lasers [7] and mechanically tunable devices. As an example, truly tunable DFB lasing in liquid-crystalline elastomers [8] has been demonstrated recently.In previous papers we demonstrated DFB structures produced via interference lithography in films of the copolymer poly[styrene-co-(4-vinylbenzyl thiocyanate)]. In these structures the change of the refractive index caused by the UV-induced isomerization of thiocyanate (±SCN) to isothiocyanate (±NCS) groups was employed to provide the required feedback for lasing. [9,10] Using this method, we have shown that two-dimensional gratings of different periods can be easily inscribed, providing limited tunability of the emission wavelength by rotating the substrate. [11] In the present contribution we extend the aforementioned approach by combining the photoreactivity of benzylthiocyanate units with the mechanical properties of a styrene±butadiene rubber (SBR). This allows us to fabricate elastic DFB structures whose grating period can be varied by mechanical strain (elongation/compression). Due to the elastic properties of the material, the mechanical deformation is fully reversible. The emission wavelength of the laser is correlated to the mechanical elongation and can thereby be tuned continuously within a certain range.To synthesize the elastomer, the monomer 4-vinylbenzyl thiocyanate (VBT) was prepared according to a method described earlier.[12] The monomer was then copolymerized with butadiene using a hot emulsion polymerization with K 2 S 2 O 8 as initiator. [13] This strategy was chosen as it provides a convenient and rapid preparation of a UV-sensitive elastomer suitable for holographic recording. The structure of the photo-sensitive elastomer poly[butadiene-co-(4-vinylbenzyl thiocyanate)] (PBco-VBT) is given in Scheme 1. Due to the free-radical reaction, the butadiene units are both (1,2) and (1,4) linked, with the (1,4) units being dominant. 1H NMR data showed 67 ± 2 mol-% of 1,4-linked butadiene, 12 ± 2 mol-% 1,2-linked butadiene, and 21 ± 2 mol-% of VBT units in the copolymer. This was further confirmed by elemental analysis (C, H, N, S). These data, as well as FTIR spectra, showed that no isomerization of the thiocyanate gro...

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“…This photoreaction increases the refractive index of the irradiated parts of the polymer, thus enabling the inscription of index patterns. [8,9] Gratings in these copolymers can be fabricated easily using UV interference lithography, and have turned out useful for distributed feedback (DFB) laser applications. [10,11] Obviously, the above-described polymers do not possess the charge-transporting qualities required for incorporation into an OLED.…”

Section: Full Papermentioning

confidence: 99%

Modifying the Output Characteristics of an Organic Light‐Emitting Device by Refractive‐Index Modulation

Höfler

Weinberger

Kern

et al. 2006

Adv Funct Materials

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In order to modify the output characteristics of organic light‐emitting devices (OLEDs), the optical properties of an active layer within the device are patterned without introducing any thickness modulation. For this purpose a new conjugated copolymer, which serves as a hole‐transporting material and at the same time can be index patterned using UV techniques, is synthesized. Poly(VC‐co‐VBT) (VC: N‐vinylcarbazole; VBT: 4‐vinylbenzyl thiocyanate) is prepared by free‐radical copolymerization of VC and VBT. The material contains photoreactive thiocyanate groups that enable altering of the material's refractive index under UV illumination. This copolymer is employed as a patternable hole‐transporting layer in multilayer OLEDs. Refractive‐index gratings in poly(VC‐co‐VBT) are inscribed using a holographic setup based upon a Lloyd mirror configuration. The fourth harmonic of a Nd:YAG (YAG: yttrium aluminum garnet) laser (266 nm) serves as the UV source. In this way 1D photonic structures are integrated in an OLED containing AlQ3 (tris(8‐hydroxyquinoline) aluminum) as the emitting species. It is assured that only a periodical change of the refractive index (Δn = 0.006 at λ = 540 nm) is generated in the active material but no surface‐relief gratings are generated. The patterned devices show more forward‐directed out‐coupling behavior than unstructured devices (increase in luminosity by a factor of five for a perpendicular viewing direction). This effect is most likely due to Bragg scattering. For these multilayer structures, optimum outcoupling was observed for grating periods Λ ∼ 390 nm.

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Index and Relief Gratings in Polymer Films for Organic Distributed Feedback Lasers

Cited by 38 publications

References 18 publications

Formation of Images and Surface Relief Gratings in Photosensitive Polymers Containing SCN Groups

Formation of Images and Surface Relief Gratings in Photosensitive Polymers Containing SCN Groups

Continuously Color‐Tunable Rubber Laser

Modifying the Output Characteristics of an Organic Light‐Emitting Device by Refractive‐Index Modulation

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