This PDF file contains the front matter associated with SPIE Proceedings Volume 6891, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing

The design and synthesis of symmetrical and unsymmetrical heptamethine cyanines is reported. These chromophores present significant two-photon cross section in the 1400-1600 nm spectral range. In addition, they display optical power limiting (OPL) properties. OPL curves were interpreted on the basis of two-photon absorption (2PA) followed by excited state absorption (ESA). Finally, these molecules present several relevant properties (nonlinear absorption properties, two-step gram scale synthesis, high solubility, good thermal stability), which could lead to numerous practical applications in material science (solid state optical limiting, signal processing) or in biology (imaging).

While early investigations in two-photon absorption (TPA) mainly focused on developing structure/property relationships for organic molecules with a conjugated path extending in one dimension, more recent research efforts have also included molecules containing multiple TPA-active units or with multi-dimensional conjugated backbones. However, a complete understanding of how the number and structure of branches in chromophores affect TPA properties has not yet emerged. Here, we describe chromophores consisting of four donor-substituted branches linked to an aromatic core (benzene or pyrazine) and compare them with linear analogues with only two branches (donor-Π-donor distryrylbenzenes). It is shown that this design does not lead to large enhancement of the TPA cross sections, with only a modest increase being observed going from compounds with two to compounds with four branches. It is also shown that a molecular exciton model can describe semi-quantitatively both the one-photon and the two-photon spectra of this type of multi-branched compounds. In contrast to the one-photon case, the model shows that pure additivity of the TPA cross section should not, in general, be expected when two monomer units are coupled, and that the TPA cross section of the composite molecule depends on the relative orientation of the constituent units and on the strength and sign of the coupling interaction.

We present a modified fluorescence excitation technique for the measurement of absolute two-photon absorption cross section and spectra. We take into account the variations of pulse duration and beam intensity profile as functions of excitation wavelength, which allows determining the 2PA cross section values with the absolute fidelity ±10% in a broad range of wavelengths. On the example of Rhodamine 610 in methanol we discuss various factors that can influence the accuracy of 2PA spectra. Ways how to further increase the accuracy of 2PA measurement are discussed.

The photostabilities of a series of nonlinear optical (NLO) polyimides containing two different chromophores were measured at 655 nm where the spectral response is dominated by separated chromophores rather than J-aggregation. We investigated the effect of ring-locking of the chromophore conjugated backbone, variations in the chromophore number density and the incorporation of an anti-oxidant. We found that none of these modifications altered the initial photodegradation at 655 nm.

The origin of a strongly nonlinear dependence of second order nonlinear optical properties of poled thin films of a guest-host system consisting of charge transfer chromophores in a polymer matrix, on concentration of chromophores, remains unknown. Recently Rau et al.^{1, 2} have provided evidence based on optical microscopy in favor of a new mechanism of relaxation due to an accelerated chromophore aggregation during the heating which facilitates chromophore diffusion. Aggregation is an important factor which decreases the susceptibility. Kinetic Monte Carlo technique is used for a study of a poled guest-host system (polymer matrix with dipoles) to analyze the local free volume distribution which determines the ability of a dipole to reorient. The simulations show a large degree of inhomogeneity in this parameter, which results in a jamming effect for both orientational and translational diffusion of the dipoles. The applicability of point dipoles approach at high loads is critically discussed. The emerging physical picture of the poling allows an interpretation in terms of an aggregation observed by Rau et al.

Polymers are attractive materials for optical waveguide applications due to their low cost, easy processibility and good flexibility. One of the highest priorities in the improvement of polymer optical waveguides is to develop new polymer materials possessing low optical loss, thermal stability, and refractive index controllability. Here, we present promising optical waveguide materials, i.e. calixarene polymers, which possess good optical and thermal properties. Calixarene polymer optical waveguides showed low optical loss (less than 1 dB/cm at 1.3 μm) and good thermal stability (5 wt% loss temperature : higher than 300°C). The control of refractive index of calixarene polymers was also achieved by copolymerization of calixrene with other comonomer. Calixarene molecules are originally known as an inclusion compound in host-gesut chemistry, which can bind various metal ions and organic molecules. Thus, we also investigated the binding property of calixarene polymer against trivalent europium(Eu³⁺) complex which possesses excellent luminescent characteristics. An interaction , i.e. coordination structure, is established between calixarene polymer and Eu complex, which results in an effective suppression of concentration quenching of Eu complex.

In this paper, we report the low loss (<0.06dB single-mode, <0.2dB multi-mode) 90°-bent with 1mm-bending radius optical fiber by using 12-fiber ribbon for optical interconnection systems in both the single-mode and multi-mode case. There are a lot of 90° light deflection techniques based on several types of 45° mirrors.[1]-[6] Our 90° light deflection technique is based on bending optical fiber itself.[7] This technology is easy to be adopted for optical surface mount assemblies that need light beam deflection between the vertical surface-emitting lasers or surface-receiving photodiodes and optical paths parallel to an electric circuit board. We describe the target of our developing system, concepts, difficulty of glass fiber bending by failure probability, a single-mode fiber design for small bending with low bending losses, multi-mode 90°-bent structure using polymer materials and the 80μm-cladding 125μm spacing 12-fiber ribbon for dense packaging and easy handling in narrow spaces. We also describe the 90°-bent connector which has guide-pins splice able with conventional 12MT-connector, a 5Gbit/s×12ch parallel-optical module and these characteristics. Our developing optical interconnection system include the 90°-bent with R=1mm connector and parallel module have good performances for the practical use.

A novel technique for optical switching using an optical gate for light path switching has been developed. The developed "optical switch" is capable of separating the incident signal light from the optical fibers directly, without conversion to the corresponding electrical signals, under optical gating and of outputting these optical signals to other multiple optical fibers. The separation of a signal light under optical gating is achievable by utilizing a high-speed thermal-lens effect generated in a thin-film element by applying the gating light to an organic thin-layer optical element (thermal-lens forming element). This system is capable of separating the incident signal light with performances of high throughput and low crosstalk. The application of the versatile switch described here to telecommunication involves the combination of both an originally developed optical network and a traditional Ethernet network. The optical network between a data server and a client PC is connected by a perfect optical circuit without any electronics circuit: no optics-electronics conversion within the circuit of data transfer. In this circuit, by rooting using several optically gated optical switches, the data in a server can be distributed to each client PC. A protocol of rooting is "circuit switching". The switching of optically gated optical switches in this optical circuit is controlled by an Ethernet network. In these networks, i.e., several client PCs are connected by a bus network with each optical switch. The advantages of the proposed system are suitable for a small and limited network for limited users with the uses of large-scale data transfer, especially within a domain (building and/or yard).

In this paper we present results of possible applications of a modified DNA-dye system for dynamic processing of optical information like phase conjugation or optical correlation. The system consisted of bio-polymeric matrix made of deoxyribonucleic acid (DNA) substituted with cationic surfactant molecule cetyltrimethyl-ammonium chloride (CTMA) and doped with a photochromic Disperse Red 1 dye. Fast dynamics (a single millisecond rise and fall times) of diffraction grating formation were obtained in a typical degenerate two or four wave mixing experiments. For sample excitation we used a linearly polarized light of λ = 514.5 nm delivered by an argon ion (Ar⁺) laser. Complete reversibility of the signal generation with no residual light diffraction even after longer time exposures (up to few hours) was observed.

To control thermo-optic (T-O) coefficient of polymer materials, hybrid polymer system with inorganic nanoparticles was examined. Polymer materials have high T-O coefficient but low refractive index. On the other hand, inorganic materials have low T-O coefficient but high refractive index. Then surface treated inorganic nanoparticles were dispersed into epoxy polymers. By increasing inorganic nanoparticle contents, refractive index of hybrid polymer changed and its T-O coefficient decreased.

Intensive research on optical interconnection over flexible optical circuit boards has been undertaken for such applications as high-end routers, servers and cellular phones. And these flexible optical circuit boards are expected to be used for polymer optical waveguides. This paper reports recent progress on polymer optical waveguides. It also describes a flexible stamping method, which employs a flexible film stamp made of polymeric materials. Unlike conventional hard stamps, the flexible film stamp does not require either the stamp or its substrate to be perfectly flat, which means large area stamping is easy to achieve at reduced cost. We confirmed this by replicating 50 μm multi-mode optical polymer waveguides. The propagation loss of the waveguide is fairly low at 0.06 dB/cm at a wavelength of 850 nm. This loss is sufficiently small to meet the basic requirement for optical circuit boards, and the waveguide was used to fabricate a flexible optical circuit board with MT connectors.

Novel polyimide (PI)/epoxy hybrid material for single-step photo-patterning of optical waveguides was prepared by blending of a semi-aromatic fluorinated poly(amic acid silylester) (PASE), a cycloaliphatic epoxy compound, and a photo-acid generator. A large refractive index change (δn, > 0.01), which is sufficient for multi-mode optical waveguides, was obtained between the polymer films prepared with and without UV irradiation. The refractive index change was generated by cationic reaction between the silylated carbonyl ester groups of PASE and epoxy rings, which was initiated by UV irradiation and promoted by successive thermal curing. The difference in molecular structures, which results in the refractive index changes, were characterized by FT-IR measurements, and it was clarified that the films with and without UV irradiation showed PASE and PI structures, respectively. These films exhibited high thermal stability higher than 230°C, which are desirable for waveguide fabrication for optical inter-connects and lightwave circuits. Using this hybrid material, channel-type optical waveguides were successfully fabricated by the single-step photo-patterning procedure without development by aqueous or organic solvents, which is more facile and economical for waveguide mass-fabrication.

We have been developing the optical waveguide for the multimode using the photo-bleaching property of polysilane. The refractive index of polysilane can be easily changed by exposing to UV light as photobleaching. Using this property, we can make waveguide with simple processes as spin coating, exposing and annealing. We found that this waveguide has thermal adhesive property with glass substrate. And we applied this feature to fabricate multilayered optical waveguides that have three-dimensional structure and can change the optical light at right angle.

Conductive polymers have become an extremely useful class of materials for many optical applications. We have developed an electrochemical growth method for depositing highly conductive (~100 S/cm) polypyrrole. Additionally, we have adapted advanced fabrication methods for use with the polypyrrole resulting in gratings with submicron features. This conductive polymer micro-wire grid provides an optical polarizer with unique properties. When the polymer is exposed to ionizing radiation, its conductivity is affected and the polarization properties of the device, specifically the extinction ratio, change in a corresponding manner. This change in polarization properties can be determined by optically interrogating the device, possibly from a remote location. The result is a passive radiation-sensitive sensor with very low optical visibility. The ability to interrogate the device from a safe standoff distance provides a device useful in potentially dangerous environments. Also, the passive nature of the device make it applicable in applications where external power is not available. We will review the polymer deposition, fabrication methods and device design and modeling. The characterization of the polymer's sensitivity to ionizing radiation and optical testing of infrared polarizers before and after irradiation will also be presented. These experimental results will highlight the usefulness of the conductive infrared polarizer to many security and monitoring applications.

We have fabricated and characterized polymeric slab asymmetric waveguides doped with a near-infrared-emitting dye, 2-(6-(p-dimethylaminophenyl)-2,4-neopentylene-1,3,5-hexatrienyl)-3-ethylbenzothiazolium perchlorate. Upon nanosecond photopumping, the waveguides have shown a small-signal gain coefficient of 37.2 ± 2.1 cm^-1 at 820 nm for a pump fluence of 1.57 mJ/cm² (314 kW/cm²). The loss coefficient and transparency fluence have been found to be 7.3 ± 1.0 cm^-1 at 820 nm and 0.14 mJ/cm² (28 kW/cm²), respectively. It is shown that a small-signal gain of 19.7 ± 2.3 dB is achievable in a 1.2-mm-long waveguide. Furthermore, near-infrared laser emission from self-assembled luminescent polymer microcavities has been demonstrated. The microrings are formed around silica optical fibers of varying diameters (80, 125, and 200 μm) and the larger microresonators have an overall quality factor of ~2 × 10³, which is limited by surface roughness and scattering. We illustrate how the laser threshold varies inversely with both the quality factor and the inner diameter of the microrings. The free spectral range and the intensity variation of the laser output are also presented.

Photochromic dye is expected for all-optical waveguide switches because it could change its refractive index by UV or visible light irradiation. One of photochromic amorphous molecular materials, 4-[bis(9,9-dimethylfluorene-2-yl)amino] azobenzene (BFlAB) readily formed stable amorphous glasses above room temperature without polymer dilution and it showed large refractive index change and good processability. We fabricated an all-optical 1 × 2 Y-branch waveguide switch by simple process and evaluated its optical properties and switching function.

We have prepared nanoparticles of five organic dye molecules by laser ablation of their microcrystals in poor solvents using the third harmonics of nanosecond Nd³⁺:YAG laser as an excitation light source. Their colloidal solutions were stable for longer than 1 week without any surfactants. The mean size was almost common to all the dyes (about 50 nm) and its distribution was narrow, which was confirmed by SEM observation. By applying electrophoretic deposition, the homogeneous thin film of quinacridone nanoparticles was fabricated on an indium-tin-oxide electrode. It was demonstrated that the films with different grain size and crystalline phase can be fabricated arbitrarily by using different nanoparticles. Laser ablation is also useful for crystallization of organic molecules, which was demonstrated for a representative organic nonlinear optical material.

We have prepared an dispersion of 4'-dimethylamino-N-methylstilbazolium p-toluenesulfonate (DAST) nanocrystals using the reprecipitation method and have spectroscopically measured their orientation in an electric or magnetic field. As a result, we could observe reversible and efficient contrast change that depends on the on-off of applied field. In addition, with controlling the orientation of DAST nanocrystals by the external field, the immobilization was performed using light-cured polymer and the light irradiation. These materials may be applied to the display device or polarized light filter.

The complementary tools of atomic force microscopy (AFM) and Raman spectroscopy are used to extract information on the microstructural properties of nanocomposite n-doped Si (n-Si) and Ag/n-Si films deposited on Si(111) substrates at 400 °C and 550 °C. AFM measurements indicated that Ag/n-Si films had grain sizes and roughness values one order of magnitude higher than n-doped Si films. The onset of metal-mediated crystallization of a-Si in Ag/n-Si films at ~ 400 °C is confirmed by Raman spectroscopy. Spectral Raman red-shifts of the transverse optical phonon region compared to monocrystalline silicon originate from the interplay of phonon confinement and higher defect density caused by n-type doping. Two protocols using the etchants ammonium fluoride - HF (2%::4% ) and ammonium citrate- acetic acid-hydrogen peroxide (2.5%::2.5%::2%) solutions were investigated. A comparison between non-etched and etched films showed little variability in roughness indicating retention of the microstructure.

A polymer optical amplifier with a large core was prepared by a vacuum process. The laser dye as an active compound was dispersed into the large core by a vacuum process, which can disperse organic dyes in polymers at high density preventing dye aggregation. Amplification of signal beam at 650 nm was observed by lateral pumping with a pulsed laser at 488 nm. Gain of the amplifier increased with pump energy and reached 3.74 dB/cm by pumping of 80 μJ.

In this study, we dissolved hole transport layer (HTL) material NPB in THF (tetrahydrofuran) solvant, and spin-coated the N,N'-Bis(naphthalene-l-yl)-N,N'-bis(phenyl)-benzidine (NPB) solution on the surface of Indium Tin Oxide (ITO) anode to enhance the luminance efficiency and lifetime of flexible phosphorescent organic light emitting diodes (POLEDs), where the 2,2',2''-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) was employed as hole blocking layer (HBL) and its thickness was optimized. Such an improvement in the device performance was attributed to the improved hole-electron balance. Finally, we employed 2,9-Dime-thyl-4,7-dphenyl-1,10-phenanhroline (BCP) or TPBi as hole blocking layer. The maximum luminance efficiency reaching 24.4 cd/A can be obtained.