Journal of Nonlinear Optical Physics & Materials

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A polyamic alkyl ester (PAE) was examined for the first time as a new candidate electro-optic (EO) polymer. An EO PAE was easily prepared from Disperse Red 1 (DR1) and a polyamic acid (PAA) synthesized from 2,2-bis(4-aminophenyl)hexafluoropropane and oxydiphthalic anhydride. The EO coefficient (r₃₃) of the poled EO PAE film is around 25 pm/V at a wavelength of 1.55 μm when the film is poled with an applied voltage of 150 V/μm. The EO signal is thermostable. However, the chromophore is slightly released over 150°C.

A multi-channel optical modulator with 16 independent modulators is fabricated using an electro-optic (EO) polymer with a large EO coefficient and good thermal stability. The 16-channel modulator has lumped type electrodes for modulation and heaters for thermal biasing. The device has good uniform modulation characteristics between individual modulators. The deviation of half-wave voltages is 0.2 V and that of insertion losses about 1 dB. Crosstalks range from -28 to -36 dB and extinction ratios are more than 21 dB.

A series of dendritic 2,3,4,5-tetraphenylsiloles (1–8) are prepared. Polymerizations of 4-8 are effected by transition-metal catalysts, giving linear (9-12) and hyperbranched polymers (14) in high yields. Whereas the silole polymers are practically nonluminescent when molecularly dissolved, they become emissive when aggregated in poor solvents or cooled to low temperatures. The light-emitting diodes using linear poly(silolylacetylene)s as active layers emit blue and green lights with current efficiency up to 1.45 cd/A. The hyperbranched poly(silolenearylene)s are nonlinear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that of C₆₀, a well-known optical limiter.

Complexation of ionic amphiphiles at the air–water interface by polyelectrolytes in the subphase has a pronounced effect of stabilization and deaggregation on the amphiphiles. We have effectively utilized the latter in the case of a hemicyanine dye based amphiphile. The aggregation of these amphiphiles is influenced by the rate of equilibration of the Langmuir film and the introduction of polyelectrolytes in the subphase is found to be a convenient method to suppress the aggregation. Langmuir–Blodgett films obtained by transfer of the polyelectrolyte complexed amphiphiles show enhanced second harmonic generation.

We have prepared hybrid Langmuir–Blodgett (LB) films consisting of a clay single layer and a non-amphiphilic polar molecule, 2,5-bis(p-dimethylaminocinnamylidene)-cyclopentanone. LB films deposited on solid substrates were characterized by means of UV-vis absorption spectroscopy and optical second-harmonic generation (SHG) measurements.

4-(4-dimethylaminostyryl)-1-methylpyridinium tosylate (DAST) is a very promising organic nonlinear optical (NLO) material for future optoelectronic and nonlinear optical applications, though it cannot be grown from molten state. Hence, a derivative of DAST was synthesized and mixed with DAST. The melting point of the mixed crystal decreased drastically, making it possible to grow a single crystal from molten state. In the present investigation, a mixed single crystal of DAST has been grown from molten state by vertical Bridgman–Stockbarger method.

Although nonlinear optical (NLO) polymers often exhibit very high optical nonlinearities, they have barely been applied to tentative NLO devices. The main reason lies in their high absorption losses, and this fundamental trade-off between optical nonlinearity and absorption, stems further advancement. Our theoretical analyses inform us that absorption effect is much less critical in cascaded wavelength conversion (CWC) than in second-harmonic generation (SHG), especially when absorption loss is very high at a given second-harmonic wavelength. Based on this result, we propose CWC as a more practical application of NLO polymers than SHG.

Etching dynamics of urethane–urea copolymer film was investigated by utilizing nanosecond time-resolved interferometry and tuning excitation wavelength. From the behavior of fringe pattern deformation at the irradiated areas, it is considered that irradiated polymer film was decomposed more effectively with decrease in excitation wavelength. Excitation wavelength dependence of etching dynamics of urethane–urea copolymer film was not well interpreted in terms of total energy density which was stored within the polymer film due to laser irradiation, while photochemical and photothermal processes can explain mostly the results of shorter wavelength (≤ 475 nm) and longer wavelength (≥ 530 nm) excitations, respectively.

We address issues related to quasi-phase-matched (QPM) second-harmonic generation (SHG) in nonlinear polymer waveguide for applying at optical communication. This field of research is very challenging because the high nonlinearity of polymers leads the device to operate at low pump power levels. However, key problems to this approach include difficulty of phase matching, the high propagation losses of the guided waves, and low nonlinearity contrast in the +/0 type QPM geometry. By optimizing these points on material development, waveguide design, and device fabrication, we demonstrate a QPM SHG with the best efficiency in polymer waveguide.

Nonlinear optical (NLO) polymer is emerging as a new alternative material for a wavelength converter in optical fiber communication systems. We designed and synthesized a polyetherimide-based side-chain polymer with a 4-(dialkylamino)-4′(-(styrylsulfonyl)-stilbene chromophore as a new NLO polymer. We designed and fabricated periodically-poled NLO polymer waveguides for the wavelength converter. Difference-frequency generation (DFG) process with a quasi-phase-matching (QPM) scheme was used. For the first time, we demonstrated a wavelength converter with a DFG conversion efficiency of -47 dB in the periodically-poled NLO polymer waveguides, operating at ~ 1.55 μm.

The linear electro-optic (EO) and electro-gyration (EG) effects are studied in an optically active material systems including Bi₁₂SiO₂₀ (BSO) oxide and bent-core liquid crystals. In an isotropic BSO sample, the breaking of intrinsic centro-symmetry allowed the EO modulation of the refractive index. In a mixture of bent-shaped liquid crystalline molecules having both optical activity and birefringence, the observed intensity modulation is investigated, which is related to the nonlinear optical responses of both the optical rotatory power and the birefringence. Both the linear EO and EG effects are understood in terms of the superposition principle of linear and circular birefringences.

Push-pull electro-optic polymeric Mach-Zehnder modulators with photo-bleaching induced waveguides and dual-driving electrodes operating at 1.55 μm wavelength have been demonstrated. The nonlinear electro-optic polymer used in this work was based on a phenyltetraene bridged chromophore in polycarbonate, APC-CLD1. It has been shown that the predominant photo-bleaching mechanism was a photochemical decomposition of the chromophore. The half-wave voltage of the integrated polymeric modulator was 4.5 V in a push-pull configuration with a 1.5 cm interaction length. The extinction ratio was greater than 20 dB, and the fiber-to-fiber insertion loss was 8 dB for the TM polarization at 1.55 μm wavelength.

The variation in the longitudinal second hyperpolarizability (γ) in the bond-dissociation process of a homogeneous molecule (H₂) is investigated by the finite-field (FF) approach using several ab initio molecular orbital (MO) and density functional (DF) methods. The most accurate methods (UCCSD or RCCSD) employed in this study show that the magnitude of γ value is remarkably enhanced in the intermediate dissociation region, which corresponds to the intermediate correlation regime. Such behavior suggests that the magnitudes of γ values for open-shell neutral compounds in the intermediate correlation regime are remarkably enhanced as compared to the usual closed-shell neutral systems.

In a previous paper, we investigated static second hyperpolarizabilities (γ) of 1,4-phenylendiamine (PDA) and 4,4′-diaminodiphenylamine (DADPA), which is considered to be the simplest model for extended dendrimers including linking nitrogen (N) atoms, using the ab initio molecular orbital (MO) methods.¹ The γ value was shown to be drastically changed by linking via a N atom and/or the introduction of positive charges. In this study, we investigate the applicability of the density functional (DF) methods to the calculation of γ. It is found that although the DF methods can reproduce γ value and their nonlinear enhancement for neutral state at the CCSD(T) level, they are insufficient to reproduce reliable γ values of their charged states.

New acidochromic and photochromic compounds with nonlinear optical properties have been designed and synthesized. The hyperpolarizabilities of the zwitterionic colored forms have been quantified with polarized hyper-Rayleigh scattering experiments. The static value of oxazolidino-indoline 2 is found to be as high as Disperse Red One. This opens the way to novel multi-addressable NLO-systems.

We report experimental evidence for an efficient nonlinear optical polar ordering induced by wire poling under high field conditions in thin films of the amorphous p(DR1M) side-chain azobenzene homopolymer. Unusual enhancements of the absorption coefficient and d₃₃ susceptibility along the poling direction are observed. Preliminary circular dichroism experiments have revealed the formation of a weak optically active supramolecular structure which becomes strongly active after irradiating the poled material with a circularly polarized light. Similar to a liquid-crystal polymer mesophase, it is thus possible to control the chirality in this efficiently poled amorphous achiral azobenzene polymer, in which circularly polarized irradiations with opposite handedness produce enantiomeric structures.

We investigated the Raman coherence characteristics in the solid hydrogen film deposited on a sapphire substrate. By using Raman coherence prepared with two single-frequency pulsed lasers, we generated the multiorder coherent Raman sidebands in solid hydrogen film. High-order Raman sidebands were obtained under strong pumping conditions (≥230 MW/cm²). The generated anti-Stokes(AS)–Raman sidebands extended from ultraviolet (292 nm for AS5 band) to visible (565 nm for AS1 band) region. The multiorder Raman sideband generation is thought to be due to the parametric coupling of pump and coupling lasers. The frequency conversion efficiency shows the maximum (14%) at the pumping intensity of 360 MW/cm². From the experiment that makes the multimode probe beam beat with the prepared Raman coherence, we found that the prepared Raman coherence replicates the probe beam to its Raman sidebands.

Hyper-branched chromophores were developed and attached to a polyimide backbone. The chromophore structures led to increasing chromophore concentration in polymers. Electro-optic coefficients were measured to investigate the effect of various chromophore concentrations in side chain polymers. Thermal and electric stabilities of poled polymer films were correlated with the hyper-branched structures.

The distributions of electric field and the induced second-order nonlinearity are discussed in a poling scheme where the width of a periodic electrode is shorter than the conventional coherent length. The theoretical aspects of quasi-phase matching for a subsequent experiment in second harmonic generation are analyzed. The present analysis consistently explains that the conversion efficiency can be enhanced if the electrode width is shortened, and maximized if the electrode width is optimized.

The photophysical and two-photon absorption (TPA) properties of three homologous quadrupolar and one related three-branched chromophores were investigated. Design of the quadrupoles is based on the symmetrical functionalization of a biphenyl core. Modulation of the nonlinear absorptivity/transparency/photostability trade-off can be achieved by playing with the twist angle of the core and on the spacers (phenylene-vinylene versus phenylene-ethynylene). The quadrupolar chromophores combine high TPA cross-sections, high fluorescence quantum yield and solvent sensitive photoluminescence properties. The branched structure exhibits spectrally broadened TPA in the NIR region (up to 3660 GM at 740 nm measured in the femtosecond regime) but reduced sensitivity to the environment.

Ever since researchers first probed materials with light, a natural question they have asked pertains to the strength of this interaction. Can materials be made to more strongly absorb light at certain wavelengths, thereby yielding vibrant colors? Can the nonlinear interaction between two beams be used to make an optical switching device? How efficiently can we convert the frequency of light through a nonlinear interaction? All of these questions, in effect, are the same. Equivalently, the question can be phrased as, "how large can we make the linear or the nonlinear susceptibility?" In this paper, we apply sum rules to calculate the maximum limit of the doubly resonant two-photon absorption cross-section. We find that even for a single electron system, the cross-section can exceed δ=10⁵GM.

Two-photon absorbing phenylenevinylene derivative having silyloxy moieties in electron donor units (EHSEA) was prepared. The two-photon absorption (TPA) cross-section value of this chromophore was found to be 1.93×10^-48cm⁴sec/photon at 740 nm by using TPA-induced fluorescence method with 80 fs pulse laser. The nonlinear measurement with ns scale pulses has indicated that EHSEA exhibits an efficient optical power limiting activity. We have obtained micropatterns with high resolution by TPA-induced polymerization using EHSEA as a photosensitizer.

Two novel fluorene derivatives having cationic substituents were synthesized. Two-photon absorption (TPA) properties of the derivatives were evaluated using the fluorescence-based technique with a femtosecond pulse emitted from a Ti:sapphire laser. Maximum TPA cross-sections of the compounds were estimated from the TPA spectra. Based on the results, the relationship between the TPA cross-sections and the substituent effects of the derivatives were discussed.

A simple kinetic model of temperature-dependent processes accompanying the writing and decay of diffraction gratings in a polymer matrix doped with azo-dye chromophores under illumination with spatially modulated and linearly polarized light is introduced and studied using Monte Carlo simulations. The model generalizes a recently proposed athermal kinetic model based on three-channel photoizomerization cycles of trans–cis type of azobenzene molecules and orientational redistribution and diffusion. These processes are influenced by a polymer matrix in a thermal equilibrium. The Monte Carlo simulations show the important role of temperature on the kinetic processes during building and erasure of diffraction gratings. We discuss some interesting applications for photonic devices, related to all-optical processing and storage of information using holographic methods.

We investigate the transmission properties and its photoinduced change in a one-dimensional photonic crystal slab. This periodic waveguide consist of quartz grating substrate and a thin polymer film containing a photosensitive protein bacteriorhodopsin. We propose a scheme to achieve light-controlled optical switching using the photoinduced refractive index change of bacteriorhodopsin.

We have synthesized erbium-included mesoporous materials to enhance optical amplification gain in Er³⁺-doped silica materials. Various mesoporous materials such as MCM-41, MCM-48 or SBA-15 were prepared and then erbium ions were filled into the empty pores in the mesoporous materials via sol-gel process through the external modification of the mesoporous materials. All erbium-included mesoporous materials exhibit the near infrared emission band around 1530 nm, corresponding to the characteristic ⁴I_13/2→⁴I_15/2 transition of erbium ions. The characteristic emission intensity of erbium ions increases with the concentration of Er³⁺ ions in the erbium-included mesoporous materials.

A novel type of a saturable absorber for passive mode locking was proposed. As the novel saturable absorber, we studied the thin solid films of the molecular J-aggregates of polymethyn dyes. The films of the J-aggregates were prepared using different polymethyn dyes. Linear and nonlinear optical properties of these films were investigated. Passive mode locking using these films as the saturable absorber was performed in a Nd³⁺:YAG laser. Stable generation of short pulses (pulse duration 13 ps) was achieved.

A simple and low-cost fabrication method of polymeric optical waveguides with large core sizes for plastic optical fibers is presented. The waveguides are fabricated by hot embossing with a rectangular ridge ultraviolet (UV)-cured epoxy resin stamper. The stamper is fabricated by replication of a rectangular groove mold that is made from silicone rubber replicated from a rectangular ridge original master made from thick photoresist (SU-8). A rectangular ridge shape of the original photoresist master of 1 mm size was realized by using a flattening process, which involves hot embossing before the exposure process and using a UV-cut filter during the exposure process.

Solid and hollow core polymer photonic crystal fibers (PPCFs) were fabricated by drawing preforms of stacked capillaries made of polystyrene (PS). The PPCFs consist of a solid PS core or a hollow core surrounded by periodic air holes of a hexagonal symmetry running along the length of fiber. We have demonstrated the single mode propagation of light through the solid core PPCF at wavelengths of 1.33 and 1.55 μm.

The novel modification of gold surfaces with a biotinylated polypeptide multilayer formed by nonspecific electrostatic adsorption was designed for the SPR sensing platform. The multilayer of polypeptides (poly-L-lysine and poly(aspartic acid)) was prepared onto a negatively charged self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) on gold film. The polypeptide multilayer was functionalized with biotin by directly grafting to poly(succinimide) (PSI). The specific binding of avidin to the biotinylated polypeptide multilayer (DS 2.7%) resulted in a shift in the refractive index of 0.003±9×10^-4 with a surface density of 2.9 ng/mm². This multilayer surface was found to provide a simple and effective method for the SPR sensing.

We present a new concept to adjust the transmission properties of a two-dimensional photonic crystal by photobleaching the structure. A square lattice of 500 nm lattice constant and 300 nm hole diameter was fabricated by etching air holes into a slab waveguide consisting of a polymethylmethacrylate polymer covalently functionalized with 10 mol% of the nonlinear Disperse Red 1 chromophore. While illuminating the photonic crystal with UV light the azo molecule bonds degenerate, resulting in a considerable refractive index change and a reduced slab waveguide core layer thickness. Wavelength and polarization dependent measurements show a very large shift of the dielectric band edge of 35 nm in TE and of 27 nm in TM polarization. With our novel concept it is possible to compensate fabrication inaccuracies and to trim photonic crystal transmission properties.

Supercritical CO₂ (ScCO₂) can dissolve organic materials easily just by changing temperature and pressure. This property of ScCO₂ can be applied to extract some ScCO₂-philic organic molecules from matrix material. The ScCO₂ was used to generate the meso/macro double porous structure of polyimide/polysilsesquioxane (PI/PSSQ) hybrid film. The morphology of the porous structure was measured by scanning electron microscope (SEM). Here, we demonstrate that the ScCO₂ could penetrate into the hybrid thin film and take away the small molecules, which are the by-product (CO₂) from the imidization reaction of the PI segment and the solvent remained in the PSSQ segment by sol-gel process.

Nanotubes and nanowires of π-conjugated polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) were synthesized using Al₂O₃ nanoporous template through electrochemical polymerization method. From the SEM and TEM photographs, the formation of conducting polymer nanotube (CPNT) and nanowire (CPNW) was confirmed. From FT-IR and UV/Vis absorbance spectra, we observed the effect of doping and de-doping through HF or NaOH dissolving of Al₂O₃ template. DC conductivity and I–V characteristics as a function of temperature and gate bias were measured for the CPNTs and CPNWs prepared with various synthetic conditions. Magnetic properties were measured through EPR experiments. Based on the results, we compare the intrinsic properties between bulk and nanoscale π-conjugated polymers.

Monolayer properties of 2-(3,4,5-tris-dodecyloxyl-phenyl)-[1,3,4] oxadiazole based "tripod" dye molecules, P2G, have been studied by Langmuir–Blodgett technique, UV and polarizing microscopic images. Pressure-area isotherm of P2G has transition at 17 mN/m and this transition is believed to be the orientation rearrangement of the molecules from perpendicular to horizontal with respect to the surface normal. The presence of water insoluble hydrophobic single alkyl chains causes restructuring edge-on orientation and aggregation by compression. The H-aggregated structure was observed by UV spectrometer, and the orientation effect was clearly observed by polarizing microscopic images and sum frequency generation.

The organic salt 4-N, N-dimethylamino-4′-N′-methyl stilbazolium tosylate (DAST) is a nonlinear optical crystal with superior properties for integrated electro-optical applications and THz-devices. High quality DAST single crystals have been grown by the solution growth method. The electro-optical properties were determined in the spectral range between 700 and 1535 nm (r₁₁₁=47±8 pm/V at λ=1535 nm). Several planar structuring techniques for integrated optics applications based on DAST have been investigated. The production of single crystal thin films with minimal thicknesses of 10 μm is presented as well as the channel waveguide structuring of DAST surfaces by photobleaching techniques in the depth range of 0.2 up to 2.6 μm and by femtosecond laser ablation.

New photopolymers were designed and prepared using the thermoplastic and photoreactive binders. Poly (vinylacetate-co-vinylalcohol) was used as a thermoplastic polymer binder and 3-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI) was tethered to the side chain of the above polymer. The holographic gratings were successfully fabricated in these photopolymer film samples by conventional optical interference method. The dynamic behaviors of the grating formation were studied with the change of exposure intensity. The effect of photoreaction between the polymer binder and the newly-formed polymer in the constructive region on the diffraction behavior and its stability was also investigated.

Merocyanine salts were prepared and their photochromic behavior investigated. The salts were prepared from a solution of spiropyrans in the presence of acids such as toluenesulfonic acid and dodecylbenzene sulfonic acid under irradiation of UV light and heat. The ¹H NMR spectrum confirmed the chemical structure of the merocyanine salts. The salt showed an absorption peak at 422 nm, which was blue-shifted as compared with the absorption peak at 578 nm of the merocyanine form of spiropyran. The salt form was quite stable and virtually exhibited a negative photochromism. The salt showed better fatigue resistance than the spiropyran. The photoinduced refractive index change for the salt films by a prism coupler method was estimated to be as large as 0.0055.

Multilayer nanostructural thin films through a layer-by-layer spin self-assembly method were prepared using poly(p-phenylene vinylene)/montmorillonite. Sodium montmorillonite particles exfoliated into single sheets and cationic PPV precursor and such anionic MMT plates were spin self-assembled by electrostatic attraction. Self-assembled MMT layers blocked the penetration of oxygen and moisture and they reduced the photo-oxidation of the emitting material. Spin self-assembled films showed higher environmental stability and luminescence, and their PL spectra were somewhat different from that of bulk PPV films.

We have prepared nanocomplexes composed of silver or gold nanoparticles as a core and merocyanine or phthalocyanine as a shell portion by the co-reprecipitation method. From their absorption spectra, the core metal nanoparticles seemed to interact electronically with the shell layer of organic compounds in the nanocomplexes to give different electronic states from their original states. The morphology of their nanocomplexes was observed by electron microscopies.

We apply the field enhancement effect due to plasmon polariton excitation on a metallic nanostructure in order to improve the diffraction limited spatial resolution of coherent anti-Stokes Raman scattering (CARS) microscopy. A cantilever probe tip coated with a 25 nm-thick gold film is utilized as a near-field light source to locally excite the CARS polarizations near the tip. Our CARS microscope has effectively enhanced the CARS signals and realized vibrational imaging of single-wall carbon nanotubes (SWNTs) beyond the spatial resolution of far-field CARS microscopy.

We fabricated the organic light emitting diodes (OLEDs) using 1,2-BBPE (1,2-bis-biphenyl ethene) derivatives as a blue emitting material, which was synthesized from the 4,4′-dibromo stilbene. The methyl and tert-butyl groups were incorporated at the 4″ and 4‴ positions of 1,2-BBPE: 1,2-bis(4″,4‴-dimethylbiphenyl)ethene (BMBPE) and 1,2-bis(4″,4‴-di-tert-butylbiphenyl)ethene (BTBBPE). Photo-luminescence (PL) maxima were 439 nm for BMBPE and 425 nm for BTBBPE deposited as a film with the thickness of 1000 Å. The single-layer device fabricated with BMBPE exhibited electroluminescent (EL) maxima at 440 and 422 nm. The brightness of the luminescence observed from the device was 50 cd under 19 V. The FWHM (full-width half-maximum) observed from the EL device was 55 m. The luminescence intensity generated from the OLED made with a single BBPE layer emitted low intensity light at 422 and 442 nm and the FWHM was 61 nm. The multi-layer device with NPB, Alq₃, BCP for the hole blocking layer and BTBBPE as emission material showed luminescence intensity over 2000 Cd/m². We investigated the luminescence property as a function of device structure, such as layer thickness, chemical structure dependence.

Blue light-emitting polymer/dielectric nanolayer nanocomposites were fabricated by solution intercalation method and the photoluminescence data showed that these nanolayers act as separation layers to isolate polymer chains. Furthermore the dielectric nanolayers whose aspect ratio is about 500, also acted as efficient barriers to oxygen resulting in low keto-type emission and photo-oxidation.

A new copoly(hydroxypyridine-oxadiazole) linked with 2,5-dialkoxybenzene group was prepared via simple polycondensation reaction. The polymer 4 is basically an amorphous material with thermal decomposition temperature greater than 250°C. Introduction of ethylhexyloxy groups into the rigid backbone resulted in better solubility in common organic solvents such as THF, chloroform, and DMF. UV-visible and fluorescence spectrometers were employed to investigate the optical properties both in solution and in the film state showing that the material has blue fluorescence.

Laser action at 420 nm is observed in photopumped polymer films of polystyrene (PS) doped with the hole-transporting organic molecule N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine (TPD). Measurements of the dependence of signal on the length of the pump stripe show that the mechanism responsible for the observed spectral collapse is amplified spontaneous emission (ASE). By fitting the evolution of the output intensity at 420 nm with the excitation length, gain coefficients up to 16 cm^-1 are measured.

We have designed and synthesized novel luminescent lanthanide complexes based on a naphthalene derivative. The coordination number of complexed ligands with Eu³⁺ ions is an important parameter to enhance the photoluminescence (PL) intensity. The photoluminescence spectra of Eu(III)-cored complexes exhibit a sharp red emission band at 612 nm, corresponding to the ⁵D₀→⁷F₂ transition of the trivalent Eu ion. The saturated europium complexes (C-2 and C-3) have much stronger PL intensity than the unsaturated 6-coordinated europium complex (C-1), due to the instability of the C-1 complex. In this paper, the synthesis and photophysical properties of novel europium(III)-chelated complexes based on a naphthalene derivative will be discussed.

We fabricated all-polymer based flexible field effect transistors (FETs) using poly (3,4-ethylenedioxythiophene) (PEDOT) or polypyrrole (PPy) as the active layer and gate electrode. Polyvinyle cinnamate (PVCN) and epoxy were used for a dielectric layer. The PEDOT and PPy as the active layer and electrode were patterned through simple photo-lithography, and PVCN and epoxy as insulating layers were coated by using a spin-coater. We estimated the threshold voltage and trans-conductance through measuring the drain-source current (I_ds) as a function of gate bias (V_g). We suggest that ionic motion in the active layer plays an important role for electrical properties.

A series of random copolymers of 2,7-dibromo-9,9-bis(4′-n-octyloxyphenyl) fluorene (BOPF) and 2,7-dibromo-N-(2′-ethylhexyl)carbazole (EHC) were synthesized through Ni(0)-mediated polymerization. Carbazole comonomer was introduced to improve the hole-transporting properties of PBOPF. The synthesized poly(BOPF-co-EHC)s showed similar UV-visible absorption and PL emission to PBOPF. EL devices were fabricated in an ITO/PEDOT/polymer/Ca/Al configuration. EL devices which used copolymers showed improved device performance over devices which used PBOPF homopolymers due to a more balanced charge transport.

For most practical applications, it is essential to fabricate micro- or nano-scale polymer electroluminescent (EL) devices and pixel arrays. Microcontact printing, which uses a patterned elastomer (usually PDMS) as the mold to generate or transfer the pattern offers immediate advantages. Here we describe a method of patterning polymeric EL materials based on microcontact printing using PDMS mold. In this technique, we use the self-assembled monolayer (SAM) system of alkanephosphonic acids on ITO substrate, and patterned EL polymer is formed on the SAM-modified ITO substrate.

The blue light-emitting material was synthesized. With the non-doped, blue-emitting material in the multilayer device structure, it was possible to achieve the luminous efficiency of 3.38 cd/A at 110 mA/cm². The EL spectrum of the ITO/CuPc/NPB/BDPSP/Alq₃/Mg:Ag device showed a narrow emission band with full width at half maximum (FWHM) 70 nm and λ_max=448.25 nm. The emitting color of the device showed the highly pure blue emission (x,y)=(0.158, 0.10) for ITO/CuPc/NPB/BDPSP/Alq₃/Mg:Ag in CIE (Commission Internationale de l'Eclairage) chromaticity coordinates.