Plane-parallel poled, low loss, channel waveguides are fabricated with a large poling field (200V/μm) in 4-dimethylamino-4'-nitrostilbene (DANS) side-chain polymers. The parallel poled film leads to efficient nonlinear optical applications for TE guided Modes. We demonstrate surface emitting second harmonic generation due to mixing of counter propagating waves with this film.

Novel difunctional barbituric acid methine dyes have been synthesized for nonlinear optical applications. These Molecules have been reacted with Multi-functional isocyanates resulting in cross-linked polyurethanes. The thermal stability of the dye in crystalline form as well as dissolved in poly (Methylmethacrylate) was studied. Results suggest that although the dye crystals were thermally stable to 300 °C, when dissolved in a polymer the stability was markedly lower.

Quantum Many-electron calculations based on Multiple-excited configuration interaction have been implemented on squaraine Molecules. It is found that certain squaraines possess negative third order optical susceptibilities (γ) even in the zero frequency limit. Our calculations agree well with the experimental results obtained by Dirk and co-workers[1] for anilinium squarylium (BSQ) in terms of the sign and Magnitude. High-lying two-photon states in squaraines are found to be always critically important. The sign of γ is found to depend on the electron donating ability of the two side groups in squaraines.

Dispersive optical bistability in a Fabry-Perot (F-P) cavity with a third order nonlinear optical polymer was demonstrated. This effort involved the development of several nonlinear optical polyimides and an evaluation of their linear optical and nonlinear optical properties. These Materials were processed into waveguiding films having good homogeniety and optical properties. Several of these films were shown to have desirable third order nonlinearities, while exhibiting good mechanical and environmental stability. Characterization of these materials involved the measurement of their absorption profiles, film thicknesses, optical waveguide propagation constants and nonlinear optical susceptibilities. Based on the measured results, a specific polyimide was chosen and used to demonstrate an all-optical instrinsic bistable device operating at a wavelength of 1.06 μ. Using ∼ 100 ps input pulse widths at 1.06 μ, dispersive optical bistability originating from the induced refractive index change, δn, due to an electronic nonlinearity of the polyimide was observed.

Bipolaron-like dications have been produced in both diphenyl and bis-thienyl polyenes by oxidative doping in solution. However, until now spectroscopie studies of the charge state generation beyond the hexaene have been precluded due to lack of solubility and processibility. We have now been able to extend these studies to the decaene by incorporating solubilizing substituents on the thienyl end caps. For the neutral species, degenerate four wave Mixing (DFWM) studies indicate that χ(3) is still increasing as a function of conjugation length. Introduction of mesomerically interactive RS groups on the thiophene rings further increases both solubility and optical nonlinearity.

The wavelength dependence of the nonlinear absorption for lead tetrakis (cumyl-phenoxy) phthalocyanine (PbPc(CP)4) and lead octa (α-pentoxy) napthalocyanine (PbNc(α-PO)8) are reported. The ground state absorption and the reverse saturable absorption are substantially red shifted in PbNc (α-PO)8 as expected. Such control over the reverse saturable absorption is crucial to design optical limiting materials for specific wavelength ranges.

The objective of this investigation was to develop stable nonlinear optical (NLO) Materials which possess both second and third order NLO properties. These Materials were envisioned as having a polydiacetylene (PDA) backbone with a second order active NLO chromophoric substituent consisting of a donor group, a π-conjugated bridge, and an acceptor group. The choice of a PDA backbone in this investigation was twofold. In terms of third order NLO properties, the extensive π-conjugation of the PDA backbone leads to large ultrafast third order effects. In terms of second order NLO properties, the high thermal stability and rigidity of the PDA Matrix in a perfect polymeric single crystal is expected to prevent the randomization of the NLO chromophores in the noncentrosymmetric environment. This paper focuses on the synthesis and NLO properties of the unsymmetrical diacetylene Monomers, ((9-Butoxy carbonyl) Methyl urethanyl) -l- (4-urethanyl-4'-nitrobiphenyl) -nona-2,4-diyne, and ((9-Butoxy carbonyl) Methyl urethanyl) -l- (4-urethanyl-4'-nitroazobenzene) -nona-2,4-diyne. The high entropy flexible urethanyl side group was chosen to satisfy the monomer packing requirements for polymerization and enhance the solubility of the PDAs.

We report in this short paper a preliminary account on the design, preparation, optical characterization and photoexcitation of a class of novel conjugated polymers consisting of regularly alternating thiophene and benzene sequences, which Might represent Models for one-dimensional superlattices. Optical absorption and emission spectra suggest that the barriers produced by the phenylene Moieties do not interrupt the conjugation but can produce localization effects. Resonant Raman spectra indicate that a selective response of the thiophene Moiety occurs upon excitation with visible light. Moreover these Measurements confirm the presence of a confinement on the thiophene blocks, while the biphenil Moiety does not appear to feel the energy barrier and behaves as the corresponding polymer poly (paraphenylene) (PPP). CW photomodulation spectra show that the formation of long-lived bipolarons takes place only if the thienylenic Moiety is long enough to accomodate the lattice distortion.

Fluorescence depolarization studies of polysilane chains in solution have shown that energy transfer along the polymer chains occurs for only a very short time relative to the excited state lifetime and only over short distances before the excited states become trapped in long, low-energy segments. However, in solid films we have shown in previous work that excitons are highly Mobile throughout their 600 ps lifetime at room temperature, presumably because energy transfer among neighboring, parallel chain segments becomes possible. In this paper we report that the exciton-exciton annihilation rate constant decreases by only a factor of five between room temperature and 12 K, showing that the excitons do not become trapped even at low temperatures.

Collective excitations, such as plasmons, rotons, electron-hole liquid, and excitonic Molecules, have been extensively studied in condensed Matter.1 Wannier excitons in inorganic semiconductors are bound by the exchange interactions between two electrons of the exciton, and the bound state of More than two excitons is not possible. We demonstrate here a new type of collective excitations,2 bound states of Multiple charge-transfer (CT) excitons. Coulomb interactions in one dimension are shown to bind a train of several (More than two) CT excitons. Experimental evidence for these new type of elementary excitations is reported in a quasi-one-dimensional CT crystal of anthracene PMDA. High density excitation by femtosecond light pulses generates Multi-exciton chains, which we refer to as excitonic n-strings with n = 1, 2, 3, etc., along the stack axis of the crystal. Both the n = 2 excitonic string (biexciton) and the n = 3 string (tri-exciton) are observed. This report provides evidence for an n > 2 exciton chain in this system.2 The stability of the n-string exciton is supported by our theoretical calculations based on the extended Hubbard Hamiltonian in one dimension.

A Modified Z-scan Method was proposed to measure nonlinear index n2 (1, t) by using white laser pulses

The Mesomorphic behaviors of some ferroelectric liquid crystalline monomers and side-chain polysiloxanes studied by X-ray diffraction Measurement, differential scanning calorimeter and polarizing Microscope. All obtained polymers exhibit wide temperature range of chiral smectic C phase including room temperature.

These Mesogenic structures contain oligooxyethylene spacers and (S)-2-Methyl-l -butyl chiral tail via a three phenyl ester linkage (i.e. -Ph-COO-Ph-Ph- or -Ph-Ph-COO-Ph-). Two series of monomers with different biphenyl group linkage position were compared. One shows a novel twisted smectic A phase, in addition to the liquid crystalline sequence (Ch→SA→Sc*) obtained between cholesteric phase and smectic A phase. It also presents an unusual smectic A and chiral smectic C phase.

All the prepared polymers present smectic Mesomorphism. As the unit of flexible oligooxyethylene spacers increases, the clearing temperature decreases and the stability of the smectic phase also increases.

We have used molecular dynamics (MD) to study the room temperature bulk phase behavior of a cyclic siloxane with a pentamethylcyclosiloxane core and biphenyl-4-allyloxybenzoate Mesogens (BCS). This Material exhibits thermotropic liquid crystalline behavior above 120 °C. Bonded and non-bonded interactions were considered and a Molecular Mechanics force field was used to model the structural anisotropy of the siloxane Molecules. Molecular clusters with and without periodic boundary conditions (pbc) were studied to investigate the effect of the finite system size on the time evolution of the molecular structure. The precise nature of the boundary conditions was found to be significant and simulations that exclude pbc were better able to model the molecular system. It was found that molecular shapes associated with low energy conformations were not cylindrically symmetric but more splayed like. An approximate measure of the shape of the mesogens was obtained by describing ellipsoids around the Mesogens, and estimating the molecular length, breadth, and width from the principal axes of the ellipsoids. The orientational order was then calculated by defining the molecular axis to be along the major principal axis.

A theory based on an elastic model and including coupling between elastic deformation and nematic order parameter as well as an interaction between crosslinks and orientation is given. The nematic order parameter and the stress tensor have been determined on elongation and as a function of temperature as well as he anisotropy of the conformation of a side chain liquid crystal elastomer on application of a mechanical stress. A transition from a turbid, low ordered polydomain phase to a transparent, Monodomain is shown to occur.

We present a theoretical study of liquid crystalline polymers in nematic solvents. We focus on the following topics: (i) Rod-like chains confined between plates, (ii) Flexible chains in a slit (iii) Nematic brushes and double-brushes (iv) Anchoring transitions. Confined and grafted chains in nematic solvents can exhibit a variety of interesting effects, including quasi-piezoelectricity and a lowering of the critical voltage for the Fréedericksz transition.

Anti-reflective optical coatings made with Teflon AF2400 had the highest laser damage thresholds recorded for physical vapor deposited coatings at the Lawrence Livermore National Laboratory damage facility. Physical vapor deposited layers of Teflon AF2400, a perfluorinated amorphous polymer, Maintained the bulk optical properties of a high transmittance from 200 nm to 1200 nm, and a low refractive index. In addition, the refractive index can be intentionally reduced by control of two common deposition parameters, deposition rate and substrate temperature. Scanning electron microscopy and nuclear magnetic resonance observations indicated that morphological changes caused the variations in the refractive index rather than compositional changes. The coatings adhered to fused silica and silicon wafers under normal laboratory handling conditions.

Photoinduced absorption spectra of different polycarbazolyldiacetylenes in the visible and infrared regions are reported. Long-lived bipolaronic defects, photogenerated by excitation above the band-gap (2.54 eV), are found responsible for the observed signals. Associated with these defects, photogenerated infrared active vibrations (IRAV) are observed as absorption bands or apparent bleachings arising from Fano-type interference. This different behaviour originates from the different degree of overlap of the IRAV Modes with the associated low-energy bipolaronic absorption.

Optical emission behavior in sol-gel-derived Materials doped with tris (4,4,4-trifluoro-l- (2′-thienyl) -l,3-butanedionato-O,O′)europium (III), Eu (ttfa)3, has been investigated by exciting the electronic levels of both europium (III) and the β-diketonate ligand (ttfa-). Energy transfer processes between the ttfa− ligands and europium (III) have been studied by time-resolved luminescence spectroscopy. The dynamic processes were compared in three sol-gel-derived host Matrices (silica, an acrylate ORMOSIL, and an epoxide ORMOSIL). Concentration dependence of the energy transfer rates was also studied.

The preparation and characterization of a new generation of optical sensors fabricated from high-temperature superconductor (HTSC) thin films is reported herein. These new hybrid devices are prepared using HTSC thin films which are coated with organic dye overlayers. These systems have been shown to respond selectively to those wavelengths which are absorbed strongly by the molecular dye. Methods for fabricating the superconductor element and depositing the dye layer are discussed. Moreover, scanning electron microscopy and resistivity versus temperature measurements are utilized to characterize these hybrid structures.

Electrochemical techniques are exploited to fabricate conductive polymer/high-Tcsuperconductor sandwich structures. In such hybrid polymer/superconductor systems, it is found that when the polymer is oxidized to its conductive state, the transition temperature (Tc) and critical current (Jc) of the underlying superconductor film are suppressed. Reversible Modulations in the values of the transition temperatures up to 50 K are noted for these structures. Upon reduction of the conductive polymer layer back to its non-conductive form, Tc is found to return to values close to those acquired for the underivatized YBa2Cu3O7-δ film. Thus, the principle of a Molecular/superconductor switch for controlling superconductivity is demonstrated.