Sputtering of TiO2 and pulse laser deposition (PLD) of Pt were performed simultaneously to build the nanocomposite with homogenous dispersion of Pt in TiO2 matrix. The films exhibited a pronounced decrease in the optical band gap energy with increasing Pt content indicating the formation of new energy states in the optical gap of TiO2 matrix. As-deposited nanocomposite films were amorphous and crystallized to Pt metal and rutile type of TiO2 after post-annealing at 600 °C. Pt nanoparticle size in the annealed nanocomposite films increased from 6 to 9 nm with the repetition rate of the laser. The photoelectrochemical measurements of the Pt/TiO2 nanocomposite films in aqueous 0.1 M Na2SO4 solution indicate that a dramatic increase in anodic photocurrent at 1.0 V vs. Ag/AgCl at the wavelength region of visible light occurred in annealed films. Pt nanoparticles in the matrix of TiO2 can play an important role in the optical and photoelectrochemical proprieties of Pt/TiO2 nanocomposite thin films.

Synthetic conditions for the preparation of amphiphilic two-photon absorptive poly(ethylene glycolated) diphenylaminofluorene[60]fullerene conjugates C60(>DPAF-PEG6) were investigated. UV-vis spectra of C60(>DPAF-PEG6) collected at the concentration of 1.0 × 10–5 M in water showed absorption bands with a slight red shift, broadened, and in a less intensity as compared with those of the bands obtained in CHCl3. These features are important characteristics of C60(>DPAF-PEG6) molecular aggregation in water. Transmission electron micrographs taken at the concentration of 1.0 × 10–5 M in H2O clearly displayed images of spherical aggregates in a diameter of 200–400 nm. That substantiated high hydrophobic intermolecular interactions between these amphiphilic molecules for assemblies in water.

Nanocomposites made of an oxide core of a wide band gap insulator, a lumophore monolayer of anthracene and an outer protecting layer of PMMA are studied regarding their luminescence properties and the influence of halides stemming either from the precursor used for synthesis or from the lumophore itself. Halide-free nanocomposites exhibit luminescence spectra resembling to that of anthracene with some significant differences concerning the intensity ratio and an additional peak at 420 nm. Nanocomposites made from chlorides show excimer-like spectra with broad maxima. In microanalysis residual chlorine can be detected. Chlorine-free oxide kernels, coated with 9, 10 dichloroanthracene exhibit luminescence spectra resembling to a superposition of the pure lumophores 9 chloro- and 9, 10 dichloroanthracene. It can be shown that the origin of the halide strongly influences, but does not quench the luminescence spectra of the powders. Suspensions of the chlorine containing nanocomposites in ethanol exhibit modified anthracene like spectra. This is a strong indication for dechlorination by proton-transfer in ethanol. Suspensions of the same material in water lead to spectra showing a superposition of exci-mer spectrum and modified anthracene spectrum. Here a partial dechlorination occurs.

Sol-gel derived photosensitive inorganic-organic hybrid materials (Photo-HYBRIMER) containing a large quantity of photoactive molecules exhibit the large changes in both refractive index (over 10-2) and volume (over 30%) on UV exposure. The materials could be used for direct fabrication of micro-optical devices using holographic interference. With the change of the beam number for holographic interference (1-beam, 2-beam, 3-beam and 4-beam interference), various typed micro-optical devices (Fresnel-type lens, 1D- and 2D-typed diffraction gratings) could be easily fabricated. Importantly, the fabricated micro-optical devices exhibited the very homogeneous surface structures and good optical performance.

The focus of the presented research lies on the synthesis of novel charged iridium(III) compounds with potential applications in light-emitting electrochemical cells. The design involves iridium(III)-based materials with polymer side-chains leading to linear light-emitting polymer arrangements.

To study the electro-optical properties of such light-emitting polymers conventional and combinatorial deposition methods are used. Straightforward screening approaches are introduced. The combinatorial efforts engage the processing via inkjet printing and the screening of the optical properties using plate reader technologies based on steady state UV-vis and fluorescence. Furthermore, the morphological properties are investigated using optical interferometry and atomic force microscopy (AFM). Overall it can be shown that novel materials can be deposited revealing high-quality thin films, which allow the screening of electro-optical features using combinatorial methods. Some initial local current density studies by AFM have also been performed to characterize the current injection and transport properties of the novel materials.

This paper describes two aspects of research aimed at harnessing the triplet energy generated in electron-hole recombination in polymer electroluminescent devices. The purpose is to design solution-processible phosphorescent organometallic triplet emitters and to design high triplet energy polymer hosts that can transfer triplet energy to the phosphorescent guests. The method employed Suzuki cross coupling reactions to incorporate either phosphorescent cores or high energy triplet monomers covalently into polymer hosts to evaluate their optoelectronic properties. The results showed (i) efficient energy transfer from polyfluorene hosts to red phosphorescent guests and (ii) that pyridine and carbazole monomers could raise triplet energies of hosts. It is concluded that these approaches offer promise in the design of solution processible electrophosphorescent materials for red and green light emitting devices.

Glancing-angle deposition (GLAD) is a fabrication method capable of producing thin films with variable porosity. The GLAD process exploits substrate shadowing and limited adatom diffusion to create isolated columns of material that collectively comprise a highly porous thin film. GLAD can be used to create chiral or helical structures with a wide range of porosity through variation of the substrate tilt angle and controlled substrate rotation. We present the effect of the deposition angle on the selective transmittance of circularly polarized light in helical thin films fabricated with the GLAD process. Transmission measurements of titanium dioxide helical films reveal two regimes of enhanced selective transmittance: one corresponding to a substrate tilt angle that produces a maximum circular birefringence and another corresponding to strong anisotropic scattering.

Previous research has demonstrated enhanced Faraday rotation in one-dimensional magnetic photonic crystals, where nonreciprocity in magneto-optical cavities is resonantly enhanced to provide optical isolation in optical paths on the scale of a few microns. In this paper, we study the nonreciprocity of two-dimensional magnetic photonic crystal resonators to allow further miniaturization and monolithic in-plane integration with current integrated optical devices. The nonreciprocal magnetic resonators are constructed by alternating the magnetization directions of the ferromagnetic domains in cavities side-coupled to photonic crystal waveguides. We show analytically that the gyrotropic splitting and the strength of the magnetic hybridization of the cavity modes are determined by the overlap integral between the domain magnetization vector and the modal cross product. With a large overlap obtained from optimizing the domain structures, we circularly hybridize two nearly degenerate modes to form a pair of counter-rotating whispering-gallery like modes, oscillating at different frequencies. As a physical realization, we synthesize two singly-degenerate circularly-hybridized modes in a two-dimensional crystal formed of a triangular air hole lattice in bismuth iron garnet with a TE bandgap. We tune the magnetic splitting and the decay constants of the rotating modes to demonstrate numerically a three-port optical circulator with a 30dB extinction bandwidth of 35GHz at 1550nm. An alternative implementation of a four-port circulator is achieved by side-coupling a point defect to two parallel waveguides. Our numerical experiments are performed with finite-difference time-domain simulations and agree well with the analytical coupled-mode theory predictions.

We study coherent oscillations of radial breathing modes in metal nanoparticles with a dielectric core. Vibrational modes are impulsively excited by a rapid heating of the particle lattice that occurs after laser excitation, while the energy transfer to a surrounding dielectric leads to a damping of the oscillations. In nanoshells, the presence of two metal surfaces leads to a substantially different energy spectrum of acoustic vibrations. The lowest and first excited modes correspond to in-phase (n=0) and anti-phase (n=1) contractions of shell-core and shell-matrix interfaces respectively. We calculated the energy spectrum as well as the damping of nanoshell vibrational modes in the presence of surrounding medium, and found that the size-dependences of in-phase and anti-phase modes are different. At the same time, the oscillator strength of the symmetric mode is larger than that in solid nanoparticles leading to stronger oscillations in thin nanoshells.

Optical switching devices, which control the current direction by light stimuli, were constructed using redox polymer nanosheet assemblies. Two kind of nanosheet-photodiode, which can operate by different light irradiation wavelength were assembled in a series so that each current direction becomes opposite. In the nanosheet photodiodes, one photodiode contains ruthenium complex as a sensitizer and the other contains anthracene. When 460 nm light was irradiated to the nanosheet assemblies, only the photodiode containing the ruthenium complex becomes active and an anodic photocurrent was observed. On the other hand, when 390 nm light was irradiated to the photodiode assemblies, only the photodiode containing the anthracene chromophore becomes active and a cathodic photocurrent was observed. This means that we can control the photocurrent direction by 460 nm and 390 nm irradiation as input signals.

Strong enhancement of the two photon absorption (TPA) cross section at 812 nm is observed for tetrakis(4-sulphonatophenyl)porphyrin diacid (H4TPPS2-) when a J-type aggregate is formed in water, in comparison to the one observed for the H4TPPS2- monomer in mixture of water, DMSO and urea. Open aperture Z-scan experiments, performed with ultra-short laser pulses, are employed to measure the TPA absorption cross section. The observed enhancement is discussed in terms of possible electronic cooperative effects in the aggregate.

The static second hyperpolarizabilities (γ) of open-shell organic nonlinear optical (NLO) systems composed of singlet diradical molecules are investigated using ab initio molecular orbital (MO) and density functional theory (DFT) methods. It is found that neutral singlet diradical systems with intermediate diradical characters tend to enhance γ as compared to those with small and large diradical characters. This suggests that the diradical character is a novel control parameter of γ for singlet diradical systems.

The time and power dependence of the optical poling process of an azo chromophore in the PMMA matrix at room temperature is investigated. A model previously proposed is used to account for the writing process of the optical poling of the chromophore/PMMA system. Theoretical predictions of the growth rate and the plateau SHG intensity are found to be in good agreement with the experimental result.

Low cost fabrication is key to the successful introduction of organic electronics and roll to roll manufacturing processes. We propose here that extending flexography into the micron size resolution regime may provide an economical commercialization path for plastic devices. Flexography is a high-speed technique commonly used for printing onto very large area flexible substrates.[1] Although low resolution and poor registration are characteristics of today's flexographic process, it has many similarities with soft lithographic techniques. This work shows that large, (12”×12”) high-resolution printing plates appropriate for use on small tag and label flexographic presses can be prepared using simple and inexpensive flexographic compatible processes. We illustrate the use of these plates for three representative soft lithographic processes: microcontact printing, replica molding, and phase shift lithography.

A series of platinum(II) di-yne complexes with the general formula [PhPt(PR3)2-C≡C-X-C≡C-Pt(PR3)2Ph] where R = Et, nBu and X = a range of extended hetero-aromatic spacer groups, have been prepared by the coupling reaction between two molar equivalents of [PhPt(PR3)2Cl] and one molar equivalent of the terminal dialkyne, HC≡C-X-C≡CH, in the presence of CuI catalyst. The complexes have been characterised by IR, NMR and optical spectroscopy. These materials, which are precursors to related platinum(II) poly-yne polymers, have been specifically designed to be incorporated into metal-molecule-metal junctions in nanoelectronic devices.

Emission light due to surface plasmon (SP) excitations has been investigated in Kretschmann configuration of prism/metal thin film/organic dye thin films by means of direct irradiation of a laser beam from air to the films. Emission light through the prism coincided with the resonant conditions of SP excitations in the configuration. It was thought that SPs on the metal surface were excited by luminescence of dye molecules close to the metal surface, and the SPs propagating along the metal surface were converted to the emission light according to the resonant conditions of SPs in the configuration. Intensities and spectra of the SP emission light through the prism strongly depended upon emission angles, nanostructures of dye films, the film thickness and mixture of two kinds of dyes.

Numerous experimental studies, mostly based on the time-of flight (TOF) technique, showed that the conductivity in organic crystals can be analysed in terms of (trap-controlled) band transport. However, recent comparative studies of TOF signals and space charge limited currents (SCLCs) in tetracene crystals revealed a striking difference in carrier mobilities estimated from TOF current transients and from SCLC curves. The analysis of the SCLC curves yielded the mobilities wildly varying within 6 orders of magnitude. Therefore, it is not always clear whether the measured current-voltage (IV) device characteristics are controlled by charge injection or by transport in the bulk. In this work, we formulate a model of dopant-assisted carrier injection across a metal/organics interface and use this model for the analysis of IV curves measured on a tetracene and perylene crystal. The model suggests the occurrence of an energetically disordered layer at the surface of an organic crystal. This might be either an amorphous phase of the same material or a crystalline layer with a high density of defects and/or impurities. Since, at variance with bulk properties, the surface of an organic crystal is poorly controlled and can be strongly modified upon the contact deposition, the model of injection-controlled IV characteristics can explain the striking difference between the TOF mobility and the apparent ‘SCLC mobility’ measured in tetracene crystals. In order to give more credence to the role of surface defects states in the dark charge transport, we compare IV characteristics measured on sandwich and coplanar structures. In the latter structure, surface states show a major contribution to the conductivity.

In this paper, we present the results of our first-principles quantum mechanical studies of the electronic structure, geometry, and linear and nonlinear optical (NLO) properties of tetrahedral Gam Nm (m=1, 4, 7, 17) atomic clusters. Our calculated results suggest that the linear and NLO properties both exhibit a strong dependence upon cluster size and shape (geometry). However, the size- and the geometry-dependences are more pronounced for the NLO properties than for the linear optical properties. For clusters containing equal numbers of Ga and N atoms, an open-structure with no network-forming ring has a much larger second-order NLO coefficient than a cluster with a closed ring structure.

We demonstrate the fabrication of a three-dimensional woodpile photonic crystal in the near-infrared regime using a layer-by-layer approach involving electron-beam lithography and spin-on-glass planarization. Using this approach we have shown that we can make structures with lattice spacings as small as 550 nm with silicon as well as gold thus allowing for fabrication of photonic crystals with omnidirectional gap in the visible and near-IR. As a proof of concept we performed optical reflectivity and transmission measurements on a silicon structure which reveal peaks and valleys expected for a photonic band gap structure. The approach described here can be scaled down to smaller lattice constants (down to ∼400 nm) and can also be used with a variety of materials (dielectric and metallic) thus enabling rapid prototyping full three-dimensional photonic bandgap based photonic devices in the visible.

Previous research in organic electro-optics has shown dramatic increases in the hyperpolarizablity of NLO chromophores. However, this large microscopic activity has not been translated to the macroscopic domain. The polymeric electro-optic (E-O) materials continue to lack the high noncentrosymmetric order of the poled chromophores within the matrix necessary for high E-O response (r33). This deficiency of order represents one major obstacle that must be overcome before E-O device commercialization can be achieved. This lack of order is partially due to the large dipole moments of high μβ chromophores, which cause the chromophores to align in a centrosymmetric fashion through intermolecular electrostatic interactions. However, quantum calculations show that when the aspect ratio between the width and length of the chromophore system is adjusted to be greater than 1.4:1 by adding bulky side groups around the center of the chromophore, it would prevent side on pairing of the chromophores. This would cause a decrease in the large areas of centrosymmetric aggregation and thus allow for easier poling of the system. Here we report the synthesis of a nanoscale NLO architecture in which dendritic moieties have been incorporated around the center of the chromophore to give a three dimensional structure in order to achieve the 1.4:1 aspect ratio and maximize the macroscopic order of the system.