Drawing on the success of the DH6-polycarbonate system, new derivatives based on the DH bridge structure, bis-1,2-(dibutoxythiophene)vinylene have been synthesized and tested. The property-structure function has been investigated, showing that location of the trifluorovinylether (TFVE) crosslinker on the chromophore has an impact on electro-optic (EO) activity as well as stability. A crosslinked polymer, IMOH_PCT-R and a linear high glass transition (Tg) analog, IMOH_HT, in combination with various DH derivatives are discussed. The temporal stability data of these systems show comparable results for both crosslinked and linear polymers, furthering the argument that the Tg of the EO material is the critical parameter in determining device lifetime.
The use of conjugated light emitting polymers (LEPs) blended in non-conjugated matrices offers an enhancement in electroluminescence efficiency in polymer light emitting diodes (PLEDs) since the aggregate quenching of the excited state emission is ameliorated. In such a scheme the matrix polymer may be developed in order to enhance the thermal, mechanical, and processing properties of the LEP blend as a whole. We have produced solution processable blends of polyfluorene (PF) based copolymers with thermally crosslinkable perfluoroarylether (PFAE) polymers and tested these materials' performance as a single emissive layer in the simplest PLED structure. Specifically we present results of blends consisting of red poly[{9,9-dihexyl-2,7-bis(1-cyanovinylene)fluorenyl-ene}-alt-co-{2,5-bis(N,N'-diphenylamino)-1,4-phenylene}] as the LEP and a novel PFAE which is thermally crosslinked as the matrix. The new PFAE has been specifically developed for low optical loss, high glass transition temperature (Tg), and solution process-ability. Once spun cast and thermally crosslinked, films of these polymer blends show increased solvent resistance and enhanced Tg due to the fluoropolymer matrix. Simple ITO/polymer/Al PLEDs of several concentration ratios are fabricated and tested in order to determine the efficacy of various matrix additions. The light-current density-voltage characteristics show either equivalent or enhanced efficiency depending on LEP/PFAE concentration. Blends of the PFAE and PF copolymer LEPs are patterned into 6μm waveguide structures utilizing the solvent resistance afforded by the crosslinked PFAE matrix.
New crosslinked clad polymers were developed for electro-optic polymer modulators with special attention paid to properties such as refractive index tunability, optical loss, and conductivity. These cured polymers showed relatively low optical loss at 1550 nm and desirable conductivity. The clads were used to fabricate electro-optic devices having mode profiles closely matched to that of optical fibers in order to reduce insertion loss. A new hardmasking technique was developed to define Mach-Zehnder rib waveguides by photolithography and dry etching with high reliability and surface smoothness. The hardmasking technique demonstrated flexibility in defining waveguides made with electro-optic polymers having different reactivity towards etchant gasses.
Studies on the influence of chromophore geometry on electro- optic coefficient/loading density and poling efficiency reveal that chromophore optical loading density is largely defined by the shape of the center of chromophore, and bulky groups at the end of chromophore is not preferable for most efficient poling of chromophore dipole. An EO coefficient of 122 pm/V at 1.06 micrometers has been achieved as a result of the systematic chromophore geometry optimization. Even high EO coefficients are expected to realized in the near future. Practical Mach-Zehnder modulators have been fabricated using CLD-1/APC material and have shown good dynamic thermal stability (120 degree(s)C), low optical loss (1.67db?cm at 1.55 micrometers ), low modulation voltage (2.4 volt, 2cm modulation length), and high extinction ratio (26dB).
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