Chichang J. Wung

Poly(p-phenylene vinylene)-silica composite: a novel sol-gel processed non-linear optical material for optical waveguides

Abstract We report here the first case (to our knowledge) of a compatible blend of an inorganic polymer, silica glass, and a π-conjugated non-linear optical polymer, poly( p -phenylene vinylene), homogeneously miscible over wide composition ranges. This composite material was prepared by combining sol-gel processing techniques applicable to the silica glass with those used for the synthesis of the organic polymer from a water/alcohol-soluble sulphonium salt precursor. In this preparation the organic polymer precursor and the inorganic sol were mixed in a common solvent and converted to the final composite material. The thermal conversion of the precursor polymer released HCl, which catalysed the gelation of the inorganic sol. The resulting composite material has been characterized by infra-red and ultra-violet/visible spectral analysis and thermogravimetric and differential scanning calorimetric analysis. The material can be cast into various forms. Thin films cast by the doctor-blading technique exhibit good optical quality and show promise for application as optical waveguides.

Study of third-order optical non-linearity and electrical conductivity of sol-gel processed silica: poly(2-bromo-5-methoxy-p-phenylene vinylene) composite

A novel sol-gel processed silica: poly(2-bromo-5-methoxy-p-phenylene vinylene)silica composite was prepared using a soluble precursor. The optical properties of this material have been investigated using u.v.-visible and FTi.r. spectroscopy. The densification process was monitored by d.s.c. and t.g.a. The third-order non-linear susceptibility χ(3) has been investigated for both the pure polymer and its sol-gel composite at 602 nm using femtosecond degenerate four-wave mixing. A relatively large χ(3) value with a subpicosecond response is observed. The electrical conductivities of AsF5 doped polymer and composite films were studied using four-probe measurement.

Characterization of sol-gel processed poly(p-phenylenevinylene) silica and V2O5 composites using waveguide Raman, Raman and FTi.r. spectroscopy

Abstract A composite of poly(p-phenylenevinylene) (PPV) with V2O5 is prepared through sol-gel processing and compared with the corresponding composite with silica. The effective conjugation length as determined by the band gap remains the same when V2O5 is chosen as a dopant, whereas the effective conjugation length is reduced in the PPV/silica composite. These composites exhibit good optical quality and show promise for optical waveguiding. The waveguide Raman spectra of these composites can be easily obtained. The refractive index of the PPV V 2 O 5 composite is higher than that of the PPV/silica composite. Furthermore, the Raman spectra do not indicate any existence of chemical bonds between the vinyl group of PPV and the glassy matrix (silica oxide or V2O5). The sol-gel processed PPV V 2 O 5 ) composite also exhibits a larger χ(3) value than that of the PPV/silica composite.

Structure and morphology of sol-gel prepared polymer-ceramic composite thin films

Abstract Poly(p-phenylene vinylene) (PPV)-silica composite thin films were prepared via the sol-gel process incorporating a water-soluble PPV precursor. After solvent evaporation, the spin-coated or quiescently cast films were cured and the PPV precursor and the silica sol were completely converted into the PPV-silica composites. Quiescently cast films show an improved wave-guiding behaviour with a χ3 value only slightly smaller than pure PPV films. Their structure consists of a nanophase-separated morphology composed of amorphous silica and paracrystalline PPV. Small-angle X-ray scattering and bright field transmission electron microscopy images indicate a random arrangement of the nanoscale domains with average domain size of approximately 4 nm. In contrast, spin-coated films show clusters and cluster-cluster aggregates approximately 100 nm in diameter. The clusters consist of particulate silica and pores, each about 3 nm in size, with the PPV contained in the pores and between the clusters. The observed morphologies are related to film preparation conditions in terms of sol-gel processing, taking the presence of the polymer into account.

Two-dimensional optical grating produced on a poly-p-phenylene vinylene/V(2)O(5)-gel film by ultrashort pulsed laser radiation.

A two-dimensional permanent transmission grating was formed on a novel polymer-gel composite film by ultrashort ( approximately 0.5-ps) and visible ( approximately 602-nm) pulsed laser radiation. With an arrangement of three noncoplanar coherent laser beams, we used two approaches to produce direct formation of a two-dimensional grating on the film. One approach is to expose the sample twice to different combinations of two beams, and the other is to expose the sample to three laser beams simultaneously. The diffraction patterns and the relative intensity distributions for different order diffraction of the two-dimensional gratings formed on the poly-p-phenylene vinylene/V(2)O(5)-gel films are analyzed for the different two-beam combinations and relative orientations among the three laser beams. The total diffraction efficiency for the incident probe laser beam into all the non-zero-order diffraction beams reaches 48%.

Sol-Gel Processed Conjugated Polymers for Optical Waveguides

Abstract Novel sol-gel processed poly(l,4-phenylene vinylene) (PPV) and poly(2,5-disubstituted-l,4-phenylene vinylene)/silica composites were prepared by a soluble precursor technique. The two PPV derivatives included in this study were poly(2-bromo-5-methoxy-l,4-phenylene vinylene) and poly(2-butoxy-5-methoxy-1,4-phenylene vinylene). The spectral characteristics of these materials have been investigated using UV-visible and FT-IR spectroscopy. The densification process was studied by differential scanning calorimetry and thermal gravimetric analyzer. The third-order nonlinear susceptibility X(3) have been investigated for the polymers themselves and their sol-gel composites at 602nm using degenerate four-wave mixing (DFWM) technique. Relatively large X(3) values (4 × 10−10 ∼ 1 × 10−9 esu) with a subpicosecond response were observed.

Sol-gel processed novel multicomponent inorganic oxide: organic polymer composites for nonlinear optics

Sol-gel processing has been used to prepare a new class of multicomponent inorganic oxide:organic polymer composites which show great promise for both second- and third-order nonlinear optics. Special processing techniques have permitted the preparation of SiO2/TiO2/organic polymer composites in which the relative composition can be judiciously varied to select the linear refractive index for applications in integrated optics. Furthermore, this composite has been doped with both inorganic and organic dopants. The composite film doped with paranitroaniline (PNA) has been successfully poled. Both second-harmonic generation and electro-optic modulation have been achieved in such a poled four-component SiO2/TiO2/Polymer/PNA composite. For third-order nonlinear optics, composites of SiO2, V2O5 with poly-p-phenylene vinylene and the derivatives have been prepared. Femtosecond degenerate four-wave-mixing studies have been conducted on such third-order materials.

Study on dynamic behaviors of resonant optical Kerr effect in poly(2,5-thienylene vinylene) film✫

Abstract We have used a CPM femtosecond laser system with an amplifier pumped by a copper vapor laser to observe the optical resonant Kerr effect in poly (2,5-thienylene vinylene) (PTV) film. The kinetics of the Kerr signal have been theoretically and experimentally studied.

Third-order optical nonlinearity of poly(thienylene vinylene)/silica sol-gel composite

Abstract In order to improve the optical quality, poly(thienylene vinylene)/silica composite was prepared by sol-gel processing techniques, and its optical nonlinearity was determined. The soluble methoxy pendant poly(thienylene vinylene)(PTV) precursor and the silica sol were homogeneously mixed in tetrahydrofuran and converted to the final composite material by heat-treatment. The resulting material have been characterized by UV-visible absorption spectra, and thermal analysis. The blue shift of λmax in the UV-visible spectra of composite materials was observed which provides an evidence of interaction between the PTV and the silica components. The third-order optical nonlinearities, χ(3), were measured as 4 × 10−9 esu and 3 × 10−9 esu for the pure PTV and PTV/silica sol-gel composite, respectively.

Third-Order Optical Nonlinearity and Conductivity of 2, 5-Disubstituted Poly(1, 4-Phenylene Vinylene) Composites with SOL-GEL Processed Inorganic Glasses

Composites of poly(1,4-phenylene vinylene) (PPV) and some of its derivatives such as poly(2-bromo-5-methoxy phenylene vinylene) (BrMPPV) and poly(2-buthoxy-5-methoxy phenylene vinylene) (BuMPPV) with sol-gel processed silica and V2O5 glasses were prepared as materials for optical waveguide and photonics applications. Optical nonlinearities of the pure polymers and the polymer/sol-gel composites were measured by the degenerate four-wave mixing technique. The x (3) values are ~ 3 × 10−10,~ 9 × 10−10, and ~ 10−9 esu for the PPV, BrMPPV and BrMPPV polymers, respectively. The composites exhibited the x (3) value scaled by the number density, but were of enhanced optical quality for waveguide application. The maximum conductivity of the PPV/sol-gel film doped with AsF5 was 0.023 S/cm.