This PDF file contains the front matter associated with SPIE Proceedings Volume 8827, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Spatially extended molecular structures, modeled as quantum graphs with one-dimensional electron dynamics, exhibit optical responses that can approach the fundamental limits. We present the results of a comprehensive study of the topological dependence of the nonlinearities of quantum graphs and show exactly how the first and second hyperpolarizability of a graph depend upon its topological class and how the hyperpolarizability tensors vary with graph geometry. We show how graphs with star motifs share universal scaling behavior near the maximum nonlinear responses and articulate design rules for quantum-confined, quasi-one dimensional systems that may be realized using molecular elements and nanowires.

While sophisticated numerical computational techniques can calculate the hyperpolarizabilities of complex molecules, it is not clear what scale invariant parameters determine a large nonlinear response. We investigate the first and second intrinsic hyperpolarizabilities of one-dimensional power-law potentials with a hybrid analytical semiclassical analysis of energy spectra and numerical calculations of eigenfunctions. By varying the exponent, we determine how key underlying properties drive the nonlinear response as the system smoothly varies from particle in a box, harmonic oscillator, point charge potential, to all multipolar Coulomb potentials. The role of the well-known pathology of the 1/x² potential is also discussed.

Alignment of dipolar chromophores lies at the heart of organic electro-optic materials research. Among all the factors (e.g., external electric field, temperature, conductivity, etc.) affecting alignment efficiency or order parameter, interchromophore electrostatic interaction has been the focus of attention in the last decade. The strength of dipole interaction is highly dependent not only on dipole moment but also on chromophore shape and chromophore number density. Antiparallel interaction is dominant in the solid state of conventional EO chromophores (long and flat) and prevents electro-optic coefficient (r33) from scaling with chromophore concentration. Despite the great amount of research along various approaches to enhancing alignment, order parameters of organic EO materials are still low (0.13- 0.2 v.s. 1 for a perfect alignment). Antiparallel interaction can be selectively attenuated by attaching bulky groups to the middle part of chromophore. However, it is synthetically challenging to provide sufficient steric protection without causing severe reduction of chromophore concentration. In this paper, we will present the first realization of atomeconomic steric protection of chromophore against H-aggregation in all directions and show evidences for the dominance of head-tail interaction over antiparallel interaction of a highly dipolar chromophore. With the novel shape, the EO coefficients of guest-host films of the chromophore do not show attenuation with increasing concentration up to 100 wt%. The dominance of head-tail interaction also enabled fabrication of optical quality thick films from the neat chromophore and allows poling induced alignment to retain at temperatures above the poling temperature – a phenomenon never observed for other chromophores.

To preserve the morphological properties of para-hexaphenyl (p-6P) based nano- bers and simultaneously tune their emission wavelength, periodic organic-organic hetero-epitaxy was utilized. Multilayer structures of p-6P and -sexithiophene (6T) have been prepared by hot wall epitaxy and analyzed by scanning force microscopy, uorescence microscopy, X-ray di raction and time resolved spectroscopy. We demonstrate that organic heteroepitaxy can be applied to produce multilayered nano- bers with high crystallinity, well de ned epitaxial relationships along di erent material phases, molecular azimuthal order, and long-range morphological homogeneity. It is shown, that it is possible to precisely control and tune the highly polarized photoluminescence emission of the nano- bers from the blue to the green and orange spectral regime by a variation of the 6T concentration. Remarkably, it is possible to prepare nano- bers emitting white polarized light.

Optical circuits are needed to achieve high-speed, high-capacity information processing. An optical waveguide is an essential element in optical circuits. Electrospun polymer fibers have diameters in the nanometer range and high aspect ratios, so they are prime candidates for small waveguides. In this work, we fabricate uniform electrospun polymer nanofibers and characterize their optical waveguiding properties. Poly(methyl methacrylate) (PMMA) solutions of different concentration that contain a small amount of Nile Blue A perchlorate (NBA) are electrospun. Uniform PMMA/NBA nanofibers are obtained from the 10 wt% solution. The fibers are covered with transparent cladding and their ends cut vertically. A laser beam with a wavelength of 533 nm is irradiated onto the fiber from the direction vertical to the fiber axis so that it scans along the fiber. Photoluminescence (PL) at the end face of individual fibers is then measured. The PL intensity decreases with increasing distance (d) between the end face of a fiber and irradiating point of the laser beam as ~exp(-αd) with a loss coefficient (α). Measurements of five individual fibers reveal α is in the range of 17–75 cm^-1.

In this work, we have demonstrated a phase modulator and a ring resonator modulator by using a thin TiO₂ and electrooptic (EO) polymer derived hybrid waveguide structure. This TiO₂ layer enables the modulators to be constituted without a top cladding, and also can enhance in-device EO coefficient from 70 to 120 pm/V. We utilized the high refractive index TiO₂ to confine a large fraction of light in the relatively low refractive index EO polymer layer. As a result, the phase modulator has a VπL of 3.3 V·cm, corresponding to 1.65 V·cm in a push-pull Mach-Zehnder interferometer structure. For the ring modulator, the resonance was observed to shift by 0.02 nm/V, and a modulation depth of 3dB was observed at the frequency response function at 20 kHz using 2 V_p-p clock signal.

We present a pseudoparticle nonequilibrium Green function formalism as a tool to study the coupling between plasmons and excitons in nonequilibrium molecular junctions. The formalism treats plasmon-exciton couplings and intra-molecular interactions exactly, and is shown to be especially convenient for exploration of plasmonic absorption spectrum of plexitonic systems, where combined electron and energy transfers play an important role. We demonstrate the sensitivity of the molecule-plasmon Fano resonance to junction bias and intra-molecular interactions (Coulomb repulsion and intra-molecular exciton coupling). The electromagnetic theory is used in order to derive self-consistent ¯eld-induced coupling terms between the molecular and the plasmon excitations. Our study opens a way to deal with strongly interacting plasmon-exciton systems in nonequilibrium molecular devices.

We review our recent results towards the development of a turnkey 3D laser printer, based on self-Q-switched microchip Nd:YAG lasers, with reproducible sub-100nm resolution, and with large-scale (cm) and fast-speed (cm/sec) capability at micron resolution. First of all, we report on line fabrication with 70nm lateral, and 150nm longitudinal resolutions without significant shrinking. This is due to the tight focusing with green visible wavelength, large numerical aperture, and excellent resin properties. Secondly, we report on two-photon sensitive photoacid generators that lead to efficient 3D microfabrication with epoxy SU-8 resin. Thirdly, we demonstrate high-speed microfabrication of large scale, millimeter size, scaffolds and cemtimeter height needle with high repetition rate (130Khz), and high average power (1W) amplified microchip laser. Finally we demonstrate the two-photon induced cross-linking of antibodies to determine the type of red blood cells in microfluidic channels.

There is a substantial interest in finding materials with high nonlinear optical (NLO) properties of materials because of its attractive applications in optical limiting for safety protections. In an effort to develop highly performing optical limiting materials, recently we have found that fluorination of graphene oxides leads to improvement in their NLO properties.

We demonstrate that a photonic crystal waveguide can be trimmed with high accuracy by electron beam bleaching of a chromophore doped polymer cladding. Using this method configurable waveguides are realized which allow for spatially resolved changes of the photonic crystal’s effective lattice constant as small as 7.6 pm. We show different examples how to take advantage of configurable photonic crystal waveguides: Shifting of the complete transmission spectrum, definition of cavities with high quality factor and tuning of existing cavities.

Grating inscription in azo-dye doped polymers is an interesting phenomenon because of its high diffraction performance and applicability to real-time 3D displays. Although some of these materials were investigated under no external electric field with symmetric optical alignments in preceding studies, they often showed a phase shift of periodic modulation of refractive index from the interference fringe formed by irradiation beams, resulting in asymmetric energy exchange between two coupled beams. The mechanism of the behavior has been usually attributed to the molecular motions triggered by trans-cis isomerization, but their details are still unknown. Therefore, studies on temporal evolution of the process and their translation into physical meaning are necessary. In order to investigate the evolution of grating inscription and phase shift, several methods have been developed. In this study, we analyzed the coupled wave equations proposed by Kogelnik, and derived general solution applicable to the system with both phase and amplitude gratings with arbitrary phase relationship. We showed that the analysis based on the equation can give a direct evidence of the phase shift between the phase and amplitude gratings if it exists. This method was applied to the fringe pattern inscribed in thick films of PMMA doped with an azo-carbazole dye, showing that observed signals indicated the phase deviation between two types of gratings.

The fabrication and characterization of a 1×4-element integrated beam former based on electro-optic (EO) polymer phase modulators (PM) is summarized including findings related to waveguide loss, near-, and far-field diffraction patterns. Based on this device, two alternate designs are proposed to improve performance: an unequally spaced 1×4- element and an equally spaced 1×8-element beam former both based on EO polymer PMs. Models of these alternative designs indicate that waveguide propagation loss and strong grating lobes, both of which degraded the performance of the initial device, can be substantially improved. The proposed approach explored by the 8-element beam former introduces novel components including strain-induced optical waveguides, hybrid integration of active and passive polymers, modified waveguide diffraction aperture, and directional coupler thermo-optic (TO) switches.

Here we describe the synthesis and characterization of a series of centro-symmetric D-π-A-π-D chromophores based on an s-indacene-1,3,5,7(2H,6H)-tetraone acceptor with conjugated linkers containing thiophene and pyrrole moieties. These materials were studied by UV visible absorption spectroscopy and their third order nonlinear optical properties investigated by z-scan at 1064 nm. The introduction of conjugated pyrrole linkers was found to give an effective third order hyperpolarizability of -1.54 x10^-30 esu, and an effective two photon absorption cross section of 6100 GM at 1064 nm. As these chromophores showed comparatively high effective nonlinear absorption they have potential in photonic applications such as optical limiting, optical communication, and for two photon initiated polymerization.

Research of nonlinear optical properties of materials for manufacturing opto-electronic devices, had a great growth in the last years. The solutions with nanoparticle metals present nonlinear optical properties. In this work we present the results of characterizing, analyzing and determining the magnitude and sign of the nonlinear refractive index, using the z-scan technique in solutions with nanoparticles of gold, lipoic acid and sodium chloride. We used a continuous Argon laser at 514 nm with variable power, an 18 cms lens, and a chopper. We determined the nonlinear refractive index in the order of 10^-9. These materials have potential applications mainly as optical limiters.

We present a study of optical, photoluminescent (PL), and photoconductive properties of small-molecule D/A bulk heterojunctions of functionalized fluorinated anthradithiophene (ADT-R-F) and pentacene (Pn-R-F8) derivatives. We chose one of the ADT derivatives, ADT-TES-F, which exhibits a 2D “brick-work” .π-stacking, as the donor, and ADT-TIPS-F (2D “brick-work”), ADT-TSBS-F (1D “sandwich-herringbone”), Pn-TIPS-F8 (2D “brick-work”), or Pn-TCHS-F8 (1D “sandwich-herringbone”), as acceptors. We measured PL and photoconductivity at time scales from sub-nanoseconds to many seconds after photoexcitation, at various acceptor concentrations, under various experimental conditions. The choice of acceptors enabled us to distinguish between effects of the LUMO energy offsets between the donor and acceptor molecules and those of the molecular packing in the acceptor domains on exciton and charge carrier dynamics.

Grating inscription in azo-dye doped polymers is an interesting phenomenon because of its high diffraction performance and applicability to real-time 3D displays. Although some of these materials were investigated under no external electric field with symmetric optical alignments in preceding studies, they often showed a phase shift of periodic modulation of refractive index from the interference fringe formed by irradiation beams, resulting in asymmetric energy exchange between two coupled beams. The mechanism of the behavior has been usually attributed to the molecular motions triggered by trans-cis isomerization, but their details are still unknown. Therefore, studies on temporal evolution of the process and their translation into physical meaning are necessary. In order to investigate the evolution of grating inscription and phase shift, several methods have been developed. In this study, we analyzed the coupled wave equations proposed by Kogelnik, and derived general solution applicable to the system with both phase and amplitude gratings with arbitrary phase relationship. We showed that the analysis based on the equation can give a direct evidence of the phase shift between the phase and amplitude gratings if it exists. This method was applied to the fringe pattern inscribed in thick films of PMMA doped with an azo-carbazole dye, showing that observed signals indicated the phase deviation between two types of gratings.

We present spectral analyses of an optical fiber waveguide containing a DNA-based solution as the optical core material, as well as separately derived optical dispersion curves for several candidate solutions. Using an Abbe refractometer and a supercontinuum light source, the visible refractive indexes of DNA-toluene, DNA-CTMA-butanol, DNA-CTMAethanol, and DNA-CTMA-HFIP solutions are measured at several concentrations and several wavelengths. The optimal solutions for light guiding are injected into hollow optical fiber waveguides, and the transmission spectra are measured by optical spectrum analyzer.

In the development of optoelectronic devices, deoxyribonucleic acid has been a representative material which has received much recent attention as a promising research area. We constructed waveguide based on optical fiber components and polydimethylsiloxane (PDMS) channel with discrete two dimensional nano-scale DNA monolayers grown by a self-assembly process and DNA complexes with cetyltrimethylammonium (DNA-CTMA) based on different kinds of solution; butanol, ethanol, and hexafluoroisopropanol. We measured the spectral profile of waveguides using a near-infrared laser source. We expect that biomaterials such as DNA-lipid complexes will have a unique application in optical devices compared with traditional fossil fuel-based polymers.

Antiparallel interaction among dipolar chromophores is the dominant force in the solid state of conventional EO chromophores (long and flat). This interaction is responsible for the formation of acentric aggregates and prevents electro-optic coefficient from scaling with chromophore concentration. Antiparallel interaction can be selectively attenuated by attaching bulky groups to the middle part of chromophore. However, it is synthetically challenging to provide sufficient steric protection without causing severe reduction of chromophore concentration. In this paper, we will present the synthesis and characterization of atom-economic ring protection of chromophores against H-aggregation and show the effect of ring protection on optical properties of the chromophores in solution and film.

The linear and second-order nonlinear optical susceptibilities of the MNA and DAN organic molecular crystals have been determined using a computationally cheap method, the Rigorous Local Field Theory, which consists in estimating the bulk properties from 1°) the corresponding molecular responses, evaluated using quantum chemistry methods, as well as 2°) the local and dressing electric fields, evaluated using a classical electrostatic interaction scheme. This study has highlighted several conditions for obtaining accurate theoretical results. First, the input molecular geometry should match the main features of the crystal structure. Then, the molecular properties should be evaluated at a correlated level since electron correlation effects are huge for the polarizability (α) and even more for the first hyperpolarizability (β). The recommended approach is to use static MP2 molecular responses together with the multiplicative scheme to describe frequency dispersion. The third important aspect is the impact of the chromophore electron density polarization due to surrounding molecules in the crystal lattice. This effect accounts for an enhancement of ca. 100-200% of β and thus influences strongly the calculated bulk χ⁽²⁾ tensor components.