This PDF file contains the front matter associated with SPIE Proceedings Volume 8258, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Graded index polymer films enable novel optics using rigid or flexible substrates, such as waveguides or anti-reflection coatings. Previously, such films have been fabricated by nanoimprint lithography or the decomposition of a single component in polymer blends. Yet, it is desirable to have precise control over the polymer film composition in order to have the most flexibility in designing refractive index profiles. Resonant-infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a polymer thin film deposition technique that enables multi-layer structures on a wide variety of substrate materials, regardless of the solubilities of constituent polymers. In this work, the feasibility of tuning the refractive index of blended polymer films of polystyrene and poly(methyl methacrylate) deposited by RIR-MAPLE is demonstrated. Different polymer blend film compositions are deposited using RIR-MAPLE by varying the polymer target ratio. Transmission electron microscopy and atomic force microscopy are used to characterize the film morphology.

Nanocrystalline cellulose solid films derived from spruce pulp exhibit iridescence when cast from chiral nematic aqueous phase suspensions of the nanocrystals. Iridescence is a color travel phenomenon that might have potential for overt encryption as an anti-counterfeiting measure. The iridescent phase also offers an intrinsic level of covert encryption by virtue of the fact that films of NCC reflect left-circularly polarized light. Addition of TINOPAL, an optical brightening agent (OBA), adds a third level of (covert) encryption potential since the chromophore exhibits strong fluorescence when excited at ultra-violet wavelengths. The overall result is a selectively polarizing fluorescent iridescent film. We study the impact of additions of OBA on NCC iridescence, optical activity, and physical structure variation with polarized optical microscopy, circular dichroism spectropolarimetry and zeta potential analysis. Increasing OBA additions increase the chiral nematic pitch of NCC films, and this in turn alters chiral nematic domain structure in the solid film. Under low concentration conditions defined by our experiments, OBA yields intense UV fluorescence, without compromising the visible light iridescent properties of the film. The potential security offered by NCC and its optical responses can be authenticated using a UV light source such as is commonly used for banknote verification, a circular polarizer in conjunction with an iridescent feature which can be verified by the eye or by chiral spectrometry.

Deoxyribonucleic acid (DNA) biopolymer has been emerging as a promising material for photonic applications. As many optoelectronic devices rely on carrier transportation to achieve desired functionality, carrier mobility is important for the exploitation of these biopolymer-based materials for practical implementation. In this study, we present the mobility measurement by employing time-of-flight technique and characterize the current-voltage (I-V) properties based on DNA-surfactant complexes. An additional NPB layer was introduced in the fabricated structure to serve as a charge generation layer (CGL). The dependency of hole mobility with respect to the applied electric field was characterized and a linear correlation was exhibited. Hole transport was found to be dispersive, indicating a high degree energetic disorder in these DNA-surfactant complexes. The characterization results show promises for the employment of DNA complexes in the applications of organic light-emitting devices and organic field-effect transistors.

White light can be obtained from Organic Light Emitting Diodes by mixing three primary colors, (i.e. red, green and blue) or two complementary colors in the emissive layer. In order to improve the efficiency and stability of the devices, a host-guest system is generally used as an emitting layer. However, the color balance to obtain white light is difficult to control and optimize because the spectrum is very sensitive to doping concentration (especially when a small amount of material is used). We use here an ultra-thin mixed emitting layer (UML) deposited by thermal evaporation to fabricate white organic light emitting diodes (WOLEDs) without co-evaporation. The UML was inserted in the hole-transporting layer consisting of 4, 4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) instead of using a conventional doping process. The UML was formed from a single evaporation boat containing a mixture of two dipolar starbust triarylamine molecules (fvin and fcho) presenting very similar structures and thermal properties and emitting in complementary spectral regions (orange and blue respectively) and mixed according to their weight ratio. The composition of the UML specifically allows for fine tuning of the emission color despite its very thin thickness down to 1 nm. Competitive energy transfer processes from fcho and the host interface toward fvin are key parameters to control the relative intensity between red and blue emission. White light with very good CIE 1931 color coordinate (0.34, 0.34) was obtained by simply adjusting the UML film composition.

We show that the optical modes of thin polymer slabs doped with J-aggregating dye molecules are strongly coupled exciton - waveguide photon modes. The hybridization appears as splitting in the dispersion relation of the fundamental transverse electric (TE) and transverse magnetic (TM) modes of the system. It is shown that these modes can be controlled by changing the thickness of the optical waveguide and by changing the concentration of the dye molecules. Leaky conical emission from the strongly coupled modes with radial and azimuthl polarizations is captured.

Developing on-chip, dynamically reconfigurable visible lasers that can be integrated with additional optical and electronic components will enable adaptive optical components. In the present work, we demonstrate a reconfigurable quantum dot laser based on an integrated silica ultra high-Q microcavity. By attaching the quantum dot using a reversible, non-destructive bioconjugation process, the ability to remove and replace it with an alternative quantum dot without damaging the underlying microcavity device has been demonstrated. As a result of the absorption/emission characteristics of quantum dots, the same laser source can be used to excite quantum dots with distinct emission wavelengths.

In this work we study optically pumped polymer-based lasers doped by various organic dyes in two different configurations, namely plane cavities of various shapes and vertical external cavities ("VECSOL"). The intrinsic fluorescence anisotropy of specific dye molecule together with the polarization state of the pump beam defines the basic emission properties of such dye-doped polymer system. The nonlinear enhancement of amplified spontaneous emission (ASE) and lasing results in the forcing of the emission properties and particularly of their polarization features. However, we demonstrate experimentally that it is possible to release this constraint and to obtain laser emission with a polarization state different from that of the pump.

We present results of studies of the systems containing photochromic molecules, for all-optical switching and amplified spontaneous emission applications. The systems consisted of: a) deoxyribonucleic acid doped with different photochromic molecules like Disperse Orange 3 or spiropyranes, and b) photochromic molecules of 4-heptyl-4'- methoxyazobenzene showing nematic liquid crystalline properties close to the room temperature (above T = 34° C). Experiments of dynamic birefringence switching were done in Optical Kerr Effect set-up, where for the sample excitation chopped cw or picosecond pulsed lasers were used. An excellent switching times and reversibility of the studied processes have been observed. The amplified spontaneous emission in luminescent dye doped biopolymeric system was achieved under the sample excitation by UV light pulses (355 nm) coming from pulsed Nd:YAG laser.

The color of the electrofluorescence switching device was tuned to white by adding extra electroactive fluorophores with different emission colors. The reversible electrochemistry of fluorophores between neutral and anion radical was accompanied by fluorescence on and off, respectively, allowing fluorescence switching. Since the fluorophores have different emission color and also different redox potential, emission color could be further modified by quenching of the particular emission with precise voltage control. A reversible multicolor switching device was prepared by packing electroactive fluorophores blend of polymer electrolyte between ITO electrodes, and its emission color was examined with various fluorophore contents and potentials.

Environmentally stable, non-toxic squarylium dyes with strong absorption maxima in the red and near infrared spectral region are known for almost fifty years. Despite the fact that their optoelectronic properties distinguish them as promising materials for organics based photovoltaic cells, they have regained attention only very recently. For their application in heterojunction solar cells knowledge of their nanoscopic morphology as well as nanoscopic electrical properties is paramount. In this paper thin films from two different squarylium dyes, from squarylium (SQ) and from hydroxy-squarylium (SQOH) are investigated. The thin films are either solution casted or vacuum sublimed onto substrates such as muscovite mica, which are known to promote self-assembly into oriented, crystalline nanostructures such as nanofibers. Local characterization is performed via (polarized) optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM).

We demonstrate the printing of a complex smart integrated system using only five functional inks: the fluoropolymer P(VDF:TrFE) (Poly(vinylidene fluoride trifluoroethylene) sensor ink, the conductive polymer PEDOT:PSS (poly(3,4 ethylenedioxythiophene):poly(styrene sulfonic acid) ink, a conductive carbon paste, a polymeric electrolyte and SU8 for separation. The result is a touchless human-machine interface, including piezo- and pyroelectric sensor pixels (sensitive to pressure changes and impinging infrared light), transistors for impedance matching and signal conditioning, and an electrochromic display. Applications may not only emerge in human-machine interfaces, but also in transient temperature or pressure sensing used in safety technology, in artificial skins and in disposable sensor labels.

An electro-optic (EO) switch based on a Fabry-Perot resonator design was fabricated and tested. The switch is comprised of two high index glass substrates with indium tin oxide (ITO) coated Bragg mirrors, surrounding an electro-optic polymer layer. The ITO top layers were patterned, the electro-optic polymer, SEO100 (Soluxra Inc.), was spun coat onto each of the two Bragg substrates, and the two samples were wafer bonded. The sandwich device was then electric field poled using a field between 80 and 90 V/μm in order to induce a second-order nonlinear optical activity in the electrooptic polymer. The experimental results done at 1.31 micron laser wavelength with a drive voltage of ±200 volts yielded a modulation depth of around 86% and 80% for frequencies of 1kHz and 10kHz, respectively.

Organic electro-optic materials, or "EO polymers," offer much higher nonlinearities than traditional crystalline materials, making these materials ideal for next generation electro-optic modulators. These materials require an additional processing step known as poling, which reorients the chromophores through the application of a high electric field. This effort will focus on corona poling, where a gas is ionized and the electric field across the sample is applied through the relocation of charged ions. The proposed technique avoids the need to raise the temperature of the material by applying the electric field while the material is deposited in solution phase. This process can overcome the thermal stability tradeoff in many organic electro-optic materials, and preliminary results indicate this process results in an enhancement in the electro-optic activity of the material.

Both nonlinear absorption and nonlinear refraction are effects that are potentially useful for a plethora of applications in photonics, nanophotonics and biophotonics. Despite substantial attention given to these phenomena by researchers studying the merits of disparate systems such as organic materials, hybrid materials, metal-containing molecules and nanostructures, it is virtually impossible to compare the results obtained on different materials when varying parameters of the light beams and different techniques are employed. We have attempted to address the problem by studying the properties of various systems in a systematic way, within a wide range of wavelengths, and including the regions of onephoton, two-photon and three-photon absorption. The objects of our studies have been typical nonlinear chromophores, such as π-conjugated molecules, oligomers and polymers, organometallics and coordination complexes containing transition metals, organometallic dendrimers, small metal-containing clusters, and nanoparticles of various kinds, including semiconductor quantum dots, plasmonic particles and rare-earth doped nanocrystals. We discuss herein procedures to quantify the nonlinear response of all of these systems, by defining and comparing the merit factors relevant for various applications.

Here, we will propose poly (cyano phenylene sulfide) as novel host materials of nonlinear optical (NLO) polymers. Our experimental results proved that NLO chromophore-doped PCPS thin films deposited on the metal layers exhibited second order NLO susceptibilities just by annealing at the temperatures higher than a glass transition point even without conventional poling procedures. We determined the optimized annealing temperatures and the film thickness for the nonelectrical poling procedure. The nonelectrical poling procedure was applicable for the films as thick as a few μm. The second order nonlinear coefficient of was 0.5 pm/V for the PCPS doped with 10w% of 4-[Ethyl(2- hydroxyethyl)amino]-4'-nitroazobenzene. Taking advantage of the unique polarization self-organization procedure, we may prepare one- or two-dimensionally periodically poled structures in these materials for the second-order NLO active photonic crystals pretty easily.

In this paper, we present the design and experimental demonstration of a high dynamic range electric field sensor based on electro-optic (EO) polymer directional coupler waveguides that offers the strong and ultra-fast EO response of EO polymer. As compared to conventional photonic electric field sensors, our directional coupler waveguide design offers several advantages such as bias-free operation, highly linear measurement response up to 70dB, and a wide electric field detection range from 16.7V/m to 750kV/m at a frequency of 1GHz.

Photopolymer based three-dimensional (3D) waveguide devices are very attractive in low-cost optical system integration. Especially, Light-Induced Self-Written (LISW) technology is suitable for this application, and the technology enables low-loss 3D optical circuitry formation from an optical fiber tip which soaked in photopolymer solution by employing its photo-polymerization due to own irradiation from the fiber tip. This technology is expected drastic mounting cost reduction in fields of micro-optic and hybrid integration devices assembly. The principle of the LISW optical waveguides is self-trapping effect of the irradiation flux into the self-organized waveguide, where, used wavelength can be chosen to fit photopolymer's reactivity from visible to infrared. Furthermore, this effect also makes possible grating formation and "optical solder" interconnection. Actually fabricated self-written grating shows well defined deep periodic index contrast and excellent optical property for the wavelength selectivity. And the "optical solder" interconnection realizes a passive optical interconnection between two faceted fibers or devices by the LISW waveguide even if there is a certain amount of gap and a small degree of misalignment exist. The LISW waveguides grow towards each other from both sides to a central point where the opposing beams overlap and are then combined into one waveguide. This distinctive effect is confirmed in all kind optical fibers, such as from a singlemode to 1-mm-corediameter multimode optical fiber. For example of complicated WDM optical transceiver module, mounted a branchedwaveguide and filter elements, effectiveness of LISW technology is outstanding. In assembling and packaging process, neither dicing nor polishing is needed. In this paper, we introduce LISW technology principles and potential application to integrated WDM optical transceiver devices for both of singlemode and multimode system developed in our research group.

The aim of this work is to analyze the propagation of the emitted light in fluorescent POFs by using the side-illumination technique. In particular, we have studied the angular distribution of the emitted light as a function of the launching angle and of the height of the incident beam. A theoretical model has been developed in order to explain the experimental measurements. A good agreement between the theoretical and the experimental results has been obtained both qualitatively and quantitatively. It is shown that both the theoretical and the experimental critical angles are appreciably higher than the meridional one corresponding to the maximum acceptance angle for a single source placed at the fiber axis. This increase changes the value of several important parameters in the performance of active fibers. The analysis has been performed in polymer optical fibers doped with a conjugated polymer.

Lab-on-chip integrated infrared spectroscopy and sensing with hybrid polymer and silicon photonic crystal slot waveguides is demonstrated for the specific and selective identification of volatile organic compounds, xylene and toluene, in water. A 300 micron long photonic crystal slot waveguide was demonstrated that enabled the detection of 100ppb xylene in water by near-infrared absorption signatures, with five times higher sensitivity on an order of magnitude smaller length scale. The on-chip absorption spectroscopy, determined by Beer-Lambert absorption law, is enabled by the combined effects of slow light and high electric field intensity enhancement in photonic crystal slot waveguides.

We present here quickly updatable hologram images using high performance photorefractive (PR) polymer composite based on poly(N-vinyl carbazole) (PVCz). PVCz is one of the pioneer materials for photoconductive polymer. PVCz/7- DCST/CzEPA/TNF (44/35/20/1 by wt) gives high diffraction efficiency of 68 % at E = 45 V/μm with fast response speed. Response speed of optical diffraction is the key parameter for real-time 3D holographic display. Key parameter for obtaining quickly updatable hologram images is to control the glass transition temperature lower enough to enhance chromophore orientation. Object image of the reflected coin surface recorded with reference beam at 532 nm (green beam) in the PR polymer composite is simultaneously reconstructed using a red probe beam at 642 nm. Instead of using coin object, object image produced by a computer was displayed on a spatial light modulator (SLM) is used as an object for hologram. Reflected object beam from a SLM interfered with reference beam on PR polymer composite to record a hologram and simultaneously reconstructed by a red probe beam. Movie produced in a computer was recorded as a realtime hologram in the PR polymer composite and simultaneously clearly reconstructed with a video rate.

Polymer has been considered to be an ideal material option for integrated photonics devices. To measure these devices, normally the route of horizontal coupling is chosen to couple the light into or out of the polymer waveguide. Due to the relatively low refractive index, implementing the surface grating coupler in this material system remains to be a challenge. In this paper, we present a polymer based surface grating coupler. Rather than expensive CMOS fabrication, the device is fabricated through a simple and fast UV based soft imprint technique utilizing self-developed low loss polymer material. The coupling efficiency is enhanced by embedding a thin Si₃N₄ layer between the waveguide core and under cladding layer. Around -19.8dB insertion loss from single-mode fiber (SMF) to single-mode fiber is obtained for a straight waveguide with grating coupler at each end. If collected with multi-mode fiber (MMF), it can be reduced to around -17.3dB. The 3dB bandwidth is 32nm centered at 1550nm. The proposed surface grating coupler and its easy fabrication method would be attractive for practical applications.

Time-resolved fluorescence polarization spectroscopy of various molecular volume fluorescein dye-labeled polymers influenced by the molecular rotation motion was investigated by picosecond dynamics measurements. The time-resolved picosecond polarization spectroscopy was modeled using a system of first-order linear differential equations containing two main parameters: the decay rate of emission and the rate of one orthogonal emission component transferring to another. Both experimental observation and theoretical calculation indicate that the fluorescent molecular rotation is the cause of the depolarization. The dipole's rotational time was extracted and shows increasing with the molecular volume obeying the Einstein-Stokes relation.

There is a continuing interest in improving electrical characteristics of an organic thin-film transistor (OTFT). One can accomplish this by controlling molecular orientations of semiconductor materials in the vicinities of an insulating layer as well as an electrode material. First, it is widely known that a self-assembled monolayer (SAM) is effective for this purpose. Second, a thin structured layer underneath an organic semiconductor material is effective for aligning the organic molecules in a specific direction. Irradiating azobenzene compounds with ultraviolet light converts trans isomers into cis-forms. When exposed to linearly-polarized ultraviolet light, the difference in the absorbance between the two isomers leads to a state where the azobenzene molecules are aligned perpendicular to the polarization direction of the ultraviolet light. Such a photo-alignment layer results in anisotropic charge transport in an OTFT and the current flow along the channel direction is enhanced. In principle, we expect that combination of these two technologies (SAM and photo-alignment) would further improve the current flow in OTFTs. In experiment, we synthesized a compound 4-(3- (trichlorosilyl)propoxy)azobenzene (Azo-SAM) and used this material to align an organic semiconductor poly(3- hexylthiophene) (P3HT). We formed the Azo-SAM on a glass substrate, spin-coated a P3HT/1, 2, 4-trichlorobenzene solution, annealed in nitrogen atmosphere and exposed it to linearly-polarized ultraviolet light. Absorbance spectroscopy in the visible range revealed anisotropy in the two samples exposed to the two polarization directions orthogonal to each other. Fabrication of organic transistors with this photo-alignment SAM is under way.

Charge transport in an organic thin-film transistor (OTFT) is controlled by many factors such as molecular packing in the semiconductor material and the contact property at the source/drain electrode. One approach utilizes an alignment layer to influence the molecular packing. Charge transport becomes anisotropic. However, additional processes are required to form such a structured layer. Solution processes offer more pathways in influencing the molecular packing. These include the use of solvent mixtures for adjusting the evaporation-induced flows, the temperature gradient in molten materials, drop-casting on tilted substrates, and other flow-induced processes. Common to these approaches is the fact that some forms of forces introduce directionality in semiconductor materials. Here, we propose to agitate organic molecules in a solution by applying ultrasound vibrations during the solvent evaporation. The vibration would translate and rotate the molecules and this might introduce ordering in the organic layer when the solvent evaporation is completed. In experiment, we fabricated bottom-contact polymer transistors by dispensing a poly(3- hexylthiophene)/1,2,4-trichlorobenzene solution on a substrate and subsequently drying it in a container immersed in an ultrasound bath. The average field effect mobility of the transistors prepared from a 0.1wt% solution with 30-min ultrasound vibration was 2.5 times higher than that of the control devices prepared without the vibration. We attribute this result to enhanced ordering of the P3HT molecules in the vibrated solution. Atomic-force microscope observation revealed longer polymer chains for the samples prepared with the vibration. We attribute this mobility enhancement to changes in molecular packing during the solvent evaporation.

Recently we synthesized 3,8,13,18-tetrachloro-2,7,12,17-tetramethoxyporphyrin and its metallo-derivatives [1]. The free-base molecule is unique owing to the presence of an electron donating methoxy group and electron withdrawing chloro group on the adjacent β- positions of each pyrrole moiety. We could synthesize these molecules through two different routes; the first route provided pure isomer, albeit in low yield, whereas the second route provided mixture of isomers with higher yield [1]. Herein we report the third-order nonlinear optical properties of these porphyrins obtained from Z-scan measurements using ~40 fs, 800 nm pulses. Open aperture data confirmed the presence of saturable absorption whereas the closed aperture data indicated a positive nonlinearity. We have compared the data of the pure isomer with that of the mixture of isomers.

We present our results of nonlinear optical properties of Tritolyl Corrole (TTC) and Triphenyl Corrole (TPC) studied in the form of solution using Z-scan technique with 660 nm, ~2 picosecond (ps) pulses and 800 nm, ~40 femtosecond (fs) pulses excitation. Picosecond open-aperture Z-scan data revealed these molecules exhibited strong saturable absorption. These molecules possessed negative nonlinear refractive index (n2). The estimated value of n2 was 6×10^-15 cm²/W and 8×10^-15 cm²/W for TPC and TTC, respectively. We have recently reported NLO properties of Corroles with 800 nm excitation where they exhibited strong two-photon absorption (2PA) at higher intensities and effective two-photon absorption at lower intensities in the ps regime. Femtosecond open aperture Z-scan studies indicated the presence of strong saturable absorption with effective nonlinear absorption coefficients (β) of ~0.8×10^-13 cm/W and ~2.7×10^-13 cm/W for TPC and TTC, respectively. We have also estimated the sign and magnitude of real part of third order nonlinearity through the closed aperture scans. We discuss the nonlinear optical performance of these organic molecules.

We performed a systematic study of the effect of processing conditions on the performance of P3HT:PCBM solar cells. We have investigated the influence of the source material, solution preparation (stirring vs. sonication), additives (such as 1,8-octanedithiol), pre-formation of P3HT nanowires, and annealing on the device performance and/or morphology and phase separation in the active layer. Furthermore, the influence of spin-coating PCBM on top of P3HT and PCBM on top of the P3HT:PCBM layer has been investigated. We found that all of these factors affect the performance of the solar cells, although there are several alternative methods which can result in similar improvements of the performance. We found that the improvement trends for various procedures (additives, PCBM top layer, P3HT nanowires, etc.) are similar and also strongly dependent on the different source materials. The main factor determining in the obtainable efficiency is the solution preparation and the source materials. Obtained results and the implications on further improvement of solar cell performance are discussed in detail.

Higher-order anisotropic self-diffraction up to third orders have been observed in Cerium doped barium titanate by using red beam at 633 nm from He-Ne laser. In our experiment, the third orders and second orders have been observed simultaneously for the first time from our knowledge. From our observation, the phase conjugate beam has not been generated before and after the appearance of higher orders as observing when the green beam from the Argon-ion laser at 514.5 nm has been used. The diffraction efficiency and the decay rate of the grating have been measured as well in the red light case.

We demonstrate cis-to-trans transition based red light holographic recording in an azobenzene-liquid crystal (LC) polymer material following efficient crucial transition of trans-to-cis, which is prepared by selected wavelength light pre-illumination. The presence and orientation of soft liquid crystal impregnating the polymer backbone allows the cis intermediate states to hold for the stable red hologram recording and non-destructive readout. Using a 50 nm bandwidth light source at the center wavelength of 575 nm, we have efficient pre-illumination on the material. The diffraction efficiency of up to 2% can be achieved by a HeNe laser at 632.8 nm wavelength, and two-dimensional holograms of USAF resolution target are successfully recorded.

We have characterised a strain and temperature sensing system being developed by Southern Photonics that uses a new Optical Interrogator and fibre Bragg gratings. We have determined the key strain and temperature coefficients, and shown that strain and temperature can be measured simultaneously. The experimental uncertainty is 5.2 pm when using the 1540 nm fibre Bragg grating, which corresponds to an experimental uncertainty in measuring the temperature of 0.54 ºC and in measuring the strain of 3.4 με. Simulations predict that a Bragg reflection of more than 90% can be achieved for Bragg Gratings in polymer thin films containing chromophores for grating lengths as small as 200 μm. A small Bragg grating length means that it should be possible to create waveguides and four Bragg gratings for strain tensor and temperature measurements within an area as small as 5×5 mm².