This PDF file contains the front matter associated with SPIE Proceedings Volume 7413, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The low, third-order nonlinear optical characteristics, as compared with the poly (3-hexylthiophene) [RRP3HT] thin film made on the fused silica substrate by the drop casting method, depend on the random orientation of the thin film prepared by the spin-coating method. The RR-P3HT thin film was made using the casting method, and in addition, the morphology of the RR-P3HT thin film and the effect on third-order nonlinear optical characteristics were evaluated and examined. The fast drying speed meant the thin film did not form by the casting method. Therefore, as the drying speed is suppressed with a saturated chloroform-gas, the RR-P3HT thin film was prepared with the same. In the RR-P3HT thin film made by the casting method, it was clarified as having third-order nonlinear optical characteristics for an excellent orientation compared with the spin-coating method. Furthermore, the third-order nonlinear optical characteristics for the orientation of the poly (3-octylthiophene)[P3OT] and poly (3-dodecylthiophene)[P3DDT] thin films were investigated and performed. The Χ⁽³⁾ of P3DDT thin film is 1.03×10^-10 [esu].

Two dimensional photonic crystal waveguides in high index materials enable integrated optical devices with an extremely small geometrical footprint on the scale of micrometers.1-3 Slotted waveguides are based on the guiding of light in low refractive index materials and a field enhancement in this particular region of the device. Here, we experimentally demonstrate electro-optic modulation in slotted photonic crystal waveguides based on silicon-on-insulator substrates covered and infiltrated with highly nonlinear guest host optical polymers.4 A photonic crystal heterostructure is used to create a cavity, while simultaneously serving as an electrical connection from the slot to the metal electrodes that carry the modulation signal.

We investigate the role of the conjugated spacer in the optimization of the first hyperpolarizability of organic chromophores. We propose a novel strategy for the optimization of the first hyperpolarizability that is based on the variation of the degree of conjugation for the bridge that separates the donor and acceptors at the end of push-pull type chromophores. The correlation between the type of conjugated spacer and the experimental nonlinear performance of the chromophores is investigated and interpreted in the context of the quantum limits.

Two photon absorption cross-sections and fluorescence dynamics of Riboflavin, Fluorescein 548, Coumarin 519 and Quinizarin adsorbed onto reactive (TiO₂) and non-reactive (ZrO₂) semiconductor nanoparticles have been investigated. These dye molecules are chosen because of their inherently different anchoring groups with which they can bind to semiconductor nanoparticles giving a handle to probe the influence of anchoring group as well as molecule-nanoparticle electronic coupling on the two-photon absorption and nonlinear optical properties. Two-photon excited fluorescence technique has been utilized to monitor the two photon absorption cross-sections and the dynamics of singlet states are followed with femto second fluorescence upconversion. Interesting cross-section trends have been observed where the TPA cross-section of chromophore on ZrO₂ surface is similar or lower to that of the free dye while the cross-sections seem to be higher on the surface of reactive TiO₂ nanoparticle surface. Fluorescence upconversion investigations were able to probe the electronic interactions of the chromophore with semiconductor nanoparticle and also the adsorption of the chromophores on the surface of the nanoparticle.

The optical, fluorescent, and photoconductive properties of solution-processable functionalized pentacene and anthradithiophene (ADT) derivatives are presented. Considerable fluorescence quantum yields of - 70-75% and ~ 40-50% were observed in several ADT derivatives in toluene solutions and in thin films, respectively. Using conventional wide-field fluorescence microscopy, ADT derivatives were successfully imaged in the polymethylmethacrylate (PMMA) matrix on a single molecule level, at 532 nm at room temperature. All films exhibited fast charge carrier photogeneration upon 100 fs 400 nm excitation and power-law decay dynamics of the transient photocurrent over many orders of magnitude in time. In solution-deposited ADT thin films, effective charge carrier mobilities calculated from the space-charge-limited currents reached ~ 0.1 cm²/Vs. In the same films, bulk photoconductive gains of up to 130 were observed at 532 nm continuous wave (cw) excitation with light intensity of 0.58 mW/cm² at the applied electric field of 4 × 104 V/cm. Effects of metal-organic interfaces on the dark current and transient and cw photocurrent are also discussed.

To develop a structure-spectroscopic property relationship in platinum acetylides having poly(aromatic hydrocarbon) ligands, we synthesized a series of chromophores with systematic variation in the number of fused aromatic rings(nFAR) and ligand topology(polyacene(L), polyphenanthrene(Z) or compact(C)). We measured ground state absorption, fluorescence and phosphorescence spectra. We also performed nanosecond and picosecond flash photolysis experiments. To extend the range of compounds in the structure-property relationship, we did DFT calculations on an expanded series of chromophores to calculate the S1 and T1 state energies. In both the DFT results and experiment, the ground state and phosphorescence spectra are a function of both nFAR and ligand topology. In the L chromophores, the S1 and T1 state energies decrease linearly with nFAR. In contrast the S1 and T1 state energies of the Z chromophores oscillate with increasing nFAR. The C chromophores have behavior intermediate between the L and Z chromophores. The picosecond transient spectra show complex behavior, having spectra reflecting intersystem crossing, vibrational cooling and solvent relaxation processes. The nanosecond transient spectra result from the T1 - Tn transition. The timeresolved spectra show no systematic variation with structure, showing more complex behavior than previously studied platinum acetylides having phenylene ethynylene ligands.

We report on our recent observation of magnetic and magneto optic properties of regioregular substituted polythiophenes. The relevance of existing mechanisms within the classical limit in cognizance of our recent magnetic and MO measurements on a set of π-conjugated polymer is also discussed.

Extensive research effort is devoted to the investigation on synthesis, physical property of conjugated molecules with pi-electronic systems. These molecules exhibit interesting electrical and optical properties useful for field effect transistor, electrical conductivity, optical nonlinearity, photovoltaic and electroluminescent properties.[1-6] Conjugated diblock copolymer possessing a rod-rod structure will be rigid rods, which dictate their assembling behaviors. Since the structure of the conjugated blocks can be modified with different functional groups, such as donor and acceptor groups, the electronic properties of the resulting diblock copolymers can be engineered to behave like semiconductor p-n junctions, offering opportunity to observe rectification effects. These properties are closely related to photovoltaic effect and can find application in solar energy harvesting. In this paper, we describe several molecular systems that show clear rectification effect. [9-12]

We discuss the use of genetically modified fluorescent proteins (FPs) and a specially engineered chromophore for nonlinear optical imaging. While it is clear that FPs can be used for two-photon fluorescence (TPF) microscopy, we show that they also exhibit a large second-order nonlinear optical response, useful for second-harmonic generation (SHG) imaging. The relation between the linear and nonlinear optical properties in a small series of FPs will be discussed. We also present a new optimized chromophore for combined TPF and SHG microscopy and we show imaging results obtained on this chromophore on a water droplet model system.

While structure-properties relationships are quite actively and successfully investigated at the molecular level of engineering of optical nonlinear responses, supramolecular structure-property relationships are an appealing field. The realization that interchromophoric interactions between strongly polar/polarizable NLO chromophores can significantly affect the NLO response of each chromophoric unit as well as promote associations has opened new dimensions for molecular design. Several elegant routes have been implemented to hinder or counterbalance dipole-dipole interactions between dipolar NLO chromophores for the elaboration of second-order materials (for SHG or electro-optical modulation). At opposite, we have implemented a reverse strategy by confining discrete numbers of NLO push-pull chromophores in close proximity within covalent organic nanoclusters with the aim to exploit interchromophoric interactions in order to achieve enhanced NLO responses. As a proof of concept, we present here the investigation of two-series of multichromophoric covalent assemblies built from NLO push-pull chromophores showing that cooperative enhancement can be achieved both for second-order optical responses (first hyperpolarizabilities) or third-order responses (two-photon absorption cross-sections).

Based on the theoretical finding that the geometry of 1:1 complexes formed between two molecules containing planar aromatic rings, governs the relative contribution of the molecular first hyperpolarizability tensor elements to the total hyperpolarizability (β), we have demonstrated how the geometry of such complexes in solution can be described. Hyper-Rayleigh scattering (HRS) technique has been used to measure the second harmonic (SH) scattered light from the complexes in a polarization resolved manner along two mutually perpendicular directions (X and Z) in the laboratory frame (XY being the plane of linear and circular polarization and Z being the direction of propagation of the polarized incident light beam). The macroscopic depolarization ratios, D and D' obtained from the polarization resolved HRS measurements are analyzed to obtain the geometry of two 1:1 electron donor-acceptor complexes between p-xylene and tetrachloro-p-benzoquinone, and durene and dichlorodicyano-p-benzoquinone. The typical values of the two depolarization ratios, D and D', for a planar molecule with C_2v symmetry are 0.2 and 0.33, respectively. The D and D' values obtained for the complexes are higher at ~0.24 and ~0.4, respectively. This implies a deviation of the complex geometry from the C_2v symmetry that is expected from a perfect cofacial or T-shape structures. Perhaps, a twisted V shape with tilt and twist between the two molecular planes would explain the geometry of the complexes.

Linear and non-linear optical properties of Manganese-phthalocyanine (MnPc) thin films in the near infrared (NIR) are reported. MnPc thin films are prepared by vapor deposition on glass and the effects of growth conditions on the optical properties are also studied. First, Morphology of the MnPc film is studied using atomic force microscope and the structure of the film is studied using theta-2theta scan X-ray diffraction. The MnPc films consist of grains with sizes of several tens of nanometers. The grain size depends on the substrate temperature of the vapor deposition process. The growth conditions also affect the reflection intensity from the {1 0 0} facet of MnPc. The films are studied using spectroscopic ellipsometry for the NIR region (1200-1800 nm) in wide wavelength range (0.6-6.5 eV) with various incidence angles (60-80°). The nonlinear optical properties of saturable absorption are also studied by the Z-scan method with a CW laser with a wavelength of 1550 nm. The substrate temperature affects Δ and ψ more drastically than the deposition rate and this is most pronounced in the NIR region. From the saturable absorption experiments, the same trend that the substrate temperature drastically affects the nonlinear coefficient of MnPc, was also evident.

Photonic crystals have become an extremely active area of research, holding much potential for improvement and miniaturization of optical technology, just like semiconductors caused a revolution in electronics. A very popular sample to study in the visible region has been the synthetic opal, made by self-assembly processes from monodisperse dielectric spheres. Its high degree of symmetry and the nature of the dielectric materials usually employed do, however, limit its effectiveness in some ways. Here, we present an experimental investigation of modifications to these materials, adding enhanced magnetic interactions with the electromagnetic field and different shapes to the photonic crystal toolbox, as well as a combination of both.

We present a novel way of optical detection of malignant cancer cell colonies by using multi-wavelength two-photon excited fluorescence from an environmentally sensitive Styryl-9M dye. We show that the two-photon excited fluorescence from colonies embedded in a tissue phantom depends on the type of cells as well as on the composition of the phantoms. We use the ratio between the fluorescence intensities excited at 1100 and 1200 nm to distinguish between samples containing no cell colonies, samples with colonies of normal cells and samples with cancer cells. The proposed method is a promising tool for non-invasive deep tissue photodetection diagnostics and for precise localization of malignant cells.

We report on the effects of introducing guest molecules into a functionalized anthradithiophene (ADT) host on the photoluminescent (PL) and photoconductive properties of solution-deposited thin films. An addition of 0.1 wt % of an ADT derivative with cyano end groups (ADT-TIPS-CN) to a fluorinated ADT derivative (ADT-TES-F) resulted in the near complete quenching of the fluorescence spectrum of the ADT-TES-F host with an enhancement in the fluorescence spectrum of the ADT-TIPS-CN guest. A markedly longer PL lifetime was noted in films containing 10% ADT-TIPS-CN guest molecules compared to both pristine ADT-TES-F and ADT-TIPS-CN films. Stronger temperature dependence of the PL quantum yield was obtained in ADT-TIPSCN/ ADT-TES-F films at low ADT-TIPS-CN concentrations than in films of pristine material, with PL decreasing with increasing temperature. Significant changes in the photoexcited charge carrier dynamics were observed on nanosecond time-scales after 400 nm 100 fs pulsed photoexcitation upon adding ADT-TIPS-CN guest molecules to the ADT-TES-F host. In contrast, no considerable change in the photocurrent was detected under continuous wave 532 nm excitation for guest molecule concetrations up to 1% of ADT-TIPS-CN in ADT-TES-F.

Polymer composite materials have considerable attention in the modern technology and are an object of numerous fundamental and scientific investigations. Polymer composite materials have advances in physical and optical properties over single materials. It is well known that the refractive index of the optical materials play an major role for all optical functional properties. The change of refractive index due to optical intensity is important for making photo-devices such as optical switching, optical memory, and logic circuits. In the present work, we have investigated the polythiophene family derivatives i.e. poly(3-octylthiophene) (P3OT) and polymethylmethacrylate (PMMA) composites materials.

New routes have been developed in tuning the nonlinear optical properties of (metallo)organic materials by established synthetic pathways. Several methods can be used to alter second-order nonlinear optical properties of materials such as pH-alteration, chemical oxidation or reduction reactions, light triggering,... However, in-situ electrochemical switching of the nonlinear optical properties of these materials opens a new and challenging research path for exploring the linear and nonlinear properties of these materials. We are reporting on combined electrochemical and (non)linear optical experiments. The electrochemical experiments have been conducted in solution and in-situ monitored by hyper-Rayleigh scattering. Also thin films are shown to be electrochemically altered and in-situ probed by second-harmonic generation.

Photoreactive polymeric materials have been investigated under one-photon (linear) and two photon (non linear) absorption conditions. A selected chromophore, 4-(N,N-diphenylamino)phenyl benzoate, was covalently attached to different polymer backbones (polystyrene, polynorbornene and polysiloxane). It is shown, that the predominant photoreaction of the chromophore is a photo-decarboxylation (extrusion of CO2) both for two-photon and one-photon conditions. The large increase in refractive index, which results from this reaction, allows the optical patterning of the polymeric systems by conventional and two-photon radiation processes. The materials were investigated by ellipsometry, UV-VIS and FT-IR spectroscopy, FT-IR and phase contrast microscopy. Under two-photon conditions, three-dimensional index structures were inscribed in the polymers, which can be used as optical waveguides.

Over the last few years two-photon based photo-processes have become an important method to generate 3D microstructures in organic materials without the use of masks and molds. The present work deals with the fabrication of optical waveguides in a flexible polysiloxane matrix for data transmission on printed circuit boards (PCB). In the developed system the waveguide core is formed by two-photon induced photo polymerization (TPIP) of selected monomers, which are dissolved in a silicone matrix. Through the photo-induced polymerization an interpenetrating network is generated, resulting in a refractive index change between the illuminated waveguide cladding and the illuminated core material. Because of the optical transparency, flexibility, chemical and thermal stability polysiloxanes were chosen as optical matrix material. Different types of phenyl methacrylates with a high refractive index were used as monomers. In order to obtain a high contrast in refractive index, the monomers were removed from non-illuminated regions in a vacuum process after laser exposure. The written optical waveguides were evidenced by phase contrast microscopy, revealing an excellent structuring behaviour of the developed material. Optical techniques e.g. cut-back measurements and light extraction tests were applied to characterize the inscribed waveguide structures and to detect the resulting optical loss. To determine the refractive index change upon UV-irradiation spectroscopic ellipsometry was applied. Thus, a difference of Δn=0.02 between the non-illuminated cladding and the illuminated core material was detected. Further, prototypes of optical interconnects on PCBs were fabricated by inscription of a waveguide bundle between a mounted laser and photo diode, resulting in the desired increase of the transmitted photocurrent after TPA structuring. In conclusion, the obtained results demonstrate that fully flexible optical interconnects are accessible by the developed process.

The development of functional solid state non-linear optical (NLO) systems for device applications is critical to several fields. Optical computing, laser hardening, 3-dimensional data storage and remote sensing are just a few of the areas advanced by the characterization of new NLO systems. One promising venue for the development of these technologies is the nano-/meso-scale self assembly of viable chromophores into tunable aggregates. Here we present a method by which individual aggregates can be quantitatively imaged by two photon fluorescence near field scanning optical microscopy (NSOM).