This PDF file contains the front matter associated with SPIE Proceedings Volume 9939, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

A pseudo-symmetric two-photon absorbing dye (1) containing a central piperazine unit substituted with (benzothiazol-2- yl)-9,9-diethylfluoren-2-yl pendant groups has been synthesized and characterized. The molecule has a two-photonabsorption cross-section of σ₂ = 140 GM in tetrahydrofuran at ~ 740 nm and shows significant solvatochromism in the excited-state fluorescence spectra. The emission spectra broaden and the maxima bathochromically shift from 411 nm to 524 nm in n-hexane and acetonitrile, respectively. Moreover, the central piperazine moiety serves as a potential chelation site for ions. Addition of copper(I) hexafluorophosphate and zinc(II) triflate in acetonitrile indicate ground-state complexation with a shift in the emission maximum from 524 nm to 489 nm and 487 nm, respectively. Interestingly, the newly formed Cu and Zn complexes are more strongly emissive than the free dye. Finally, addition of p-toluenesulfonic acid in tetrahydrofuran also blue-shifts the emission maximum, but the intensity is quenched. Due to the photophysical changes induced by addition of metal ions and protons, the dye shows promise as a potential sensor.

In order to understand electronic and conformational effects on structure-spectroscopic property relationships in platinum acetylides, we synthesized a model series of chromophores trans-Pt(PBu₃)₂(CCPhenyl-X)₂, where X = NH₂, OCH₃, diphenylamino, t-Bu, methyl, H, F, benzothiazole, trifluoromethyl, CN and nitro. We collected linear spectra, including ground state absorption, phosphorescence and phosphorescence excitation spectra. We also performed DFT and TDDFT calculations on the ground and excited state properties of these compounds. The calculations and experimental data show the excited state properties are a function of the electronic properties of the substituents and the molecular conformation.

Organic electronics have been drawing a lot of attention over the past few decades with recent commercial applications such as organic photovoltaics, OLEDs, and flexible organic displays. One of the key components for designing organic molecules suitable for electronic devices is a fundamental understanding of excitonic behaviors. Here we report on the fabrication and photoluminescence studies of crystalline thin film organic alloy systems, metal free and metal based octabutoxyphthalocyanine (MOBPc_xH₂OBPc_1-x), and metal-free H₂OBPc and octabutoxynapthalocyanine (H₂OBNc) mixtures (H₂OBNc_xH₂OBPc_1-x). Crystalline thin films of these materials were deposited using an in-house developed pen writing technique that results in macroscopic long-range order even at the ratio of x = 0.5, which is unique and important for spectroscopic studies.

Our experiments reveal that the coherent excitonic states of MOBPc_xH₂OBPc_1-x and H₂OBNc_xH₂OBPc_1-x crystalline thin films can be tuned continuously as a function of alloy concentration (0 < x < 1). Moreover, the solution-processed technique used to fabricate these crystalline thin films provides us an unprecedented advantage in designing and controlling the bandgap tunability as well as achieving the desired exciton coherent length for variety of applications.

We have established that film morphology and laser induced heating from dye absorption are important parameters in the creation of new photonastic materials. Photonastic is defined as regular, repeatable movement in a pre-programmed direction following exposure to light. This work builds upon the development of photonastic polymers of ruthenium sulfoxide complexes, where the action of bending is ascribed to phototriggered isomerization of a sulfoxide ligand in a ruthenium coordination complex that is covalently attached to polynorbornene. The bending is analyzed in terms of a bilayer cantilever model.

We report femtosecond light-induced macromolecular self-assembly (FLIMSA), which is observed when a high peak intensity femtosecond laser beam propagates through aqueous solution of pseudoisocyanine iodide (PIC) J-aggregates and induces the formation of 0.1 – 1.0 mm-size tube-like structure surrounding the laser beam, while at the same time allowing the beam to continue propagating without obstruction or scattering. The FLIMSA material is morphologically heterogeneous and gel-like and is formed at the margins rather than at the center of the beam. As a potential explanation of this effect we assume that the FLIMSA is induced by the high photon flux gradient characteristic of the femtosecond laser beam periphery. This hypothesis is corroborated by control experiments, where J-aggregate samples were illuminated with nanosecond laser sources with a varying pulse duration, power- and beam shape characteristics, but where no FLIMSA formation was observed.

Previously, we presented the experimental evidence for a degenerate frequency two beam coupling (TBC) in two photon absorbing (2PA) organic solutions. It has been well established that the two critical requirements for TBC are a nonlinear refractive index with a finite lifetime and that the interacting fields must have non-degenerate frequencies. However, degenerate frequency coupling has been shown for fields containing a time-dependent phase, i.e. a frequency chirp. This chirp can either be intrinsic to the fields or induced by self- and cross- phase modulation (S/XPM). For nanosecond pulses, the relatively small intrinsic chirp of the fields is negligible compared to the strong cumulative effects of population redistribution which generates large S/XPM. A S/XPM-mediated theoretical treatment for degenerate frequency TBC is presented along with numerical simulations using known nonlinear optical parameters to model the experimental results.

We studied the effects of two types of ultrasonic waves, shear waves and longitudinal waves, using two nonlinear optical techniques, second-harmonic generation and hyper-Rayleigh scattering. Since shear waves hardly propagate in liquids, their influence on molecules at the interface between a surface and a liquid was studied using second-harmonic generation. Longitudinal waves propagate easily in solution, thus we used hyper-Rayleigh scattering to probe the ultrasonic effects on chromophores in solution. While we did not find shear waves to alter the second-harmonic generation from chromophores at the liquid/surface interface, the longitudinal waves caused effects comparable to our earlier observations. Longitudinal ultrasound caused a strong intensity modulation of the nonlinear optical signal according to a wave-pattern.

Present-day methods for determining the performance of third-order nonlinear optical materials include Z-scan, degenerate four-wave mixing and third-harmonic generation (THG). All these techniques possess severe drawbacks; for example, in THG, since all media (air and glass walls of the cell) present a third-order effect, eliminating these contributions requires careful, complex analysis or use of vacuum chambers. We have developed nonlinear scattering as a sensitive, straightforward technique for determining the second hyperpolarizability of samples in solution. Herein, we will for the first time show the applicability of the technique to measure organometallic Ru-complexes, optimized for high nonlinear responses. The investigated compounds showed a significant second hyperpolarizability |γ|, ranging from 1.1 for the least efficient to 2.8 ∙ 10^-33 esu for the most efficient molecule, and comparable to fullerene C₆₀ in thin films. It was deemed infeasible to extract hyperpolarizabilities using a high-frequency femtosecond laser source by a modified z-scan setup, which, in contrast to nonlinear scattering, could not account for the high degree of thermal lensing present in the investigated compounds.

We measured the diffraction efficiency response of two photorefractive polymer devices according to the duration of the single laser pulse used to record the hologram. The pulse duration was varied from 6 nanoseconds to 1 second, while the pulse energy density was maintained constant at 30 mJ/cm². This changed the peak power from 5 ×10⁹ mW to 30 mW. We observed a strong reciprocity failure of the efficiency according to the pulse duration, with a reduction as large as a factor 35 between 1 second and 30 μs pulse duration. At even lower pulse duration (< 30 μs), the efficiency leveled out and remained constant down to the nanosecond exposure time. The same behavior was observed for samples composed of the same material but with and without buffer layers deposited on the electrodes, and different voltages applied during the holographic recording. We explained these experimental results based on the charge transport mechanism involved in the photorefractive process. The plateau is attributed to the single excitation of the charge carriers by short pulses (τp < 30 μs). The increase of efficiency for longer pulse duration (τp > 30 μs) is explained by multiple excitations of the charge carriers that allows longer distance to be traveled from the excitation sites. This longer separation distance between the carriers increases the amplitude of the space-charge field, and improves the index modulation. The understanding of the response of the diffraction efficiency according to the pulse duration is particularly important for the optimization of photorefractive materials to be used at high refresh rate such as in videorate 3D display.

Tunable waveguide Bragg gratings were demonstrated in PYR-3 chromophore doped polymers. We report on the fabrication and the performance of the device. Polycarbonate thin films were doped with PYR-3 (2-{3- Cyano-4- [3-(1-decyl-1 H-pyridin-4-ylidene)-propenyl]-5,5-dimethyi-5 H-furan-2-ylidene}-malononitrile) chromophore, consisting of a dihydropyridinylidene donor and three carbon atoms in the conjugated linker between donor and acceptor. Ridge waveguides were laser micro-machined into the polycarbonate film with a JPSA micromachining system equipped with a KrF excimer laser at 248 nm. Bragg gratings were inscribed into the waveguide by permanently photobleaching the PYR-3 chromophores using a phase mask to achieve narrowband reflections at wavelengths around 1550 nm. Electro-optic properties were introduced by contact poling. Applying a static external electric field leads to the shift of the reflection peak.

Faraday rotation is a magneto-optic phenomenon in which the polarization plane of light is rotated due to magnetically induced circular birefringence. It can be used in a variety of applications such as optical isolators, magnetic field sensors and current sensors. So far, most of the applications use inorganic, paramagnetic materials, which have Verdet constants up to millions of degrees per tesla per meter in the visible spectrum range. They are performant at telecommunication wavelengths, though with smaller Verdet constants, so thicker materials are used. Disadvantages of these materials are their magnetic saturation at low magnetic fields and their strong temperature dependency. Organic, diamagnetic materials on the contrary, saturate at much larger magnetic fields and are less temperature dependent. Furthermore, they also have the advantage of their flexibility and processability. Up to now, magneto-optical research on organic materials has mostly characterized materials with low magneto-optical activity in regions without absorption, but there are some exceptions. Some pi-conjugated polymers have been shown to have very large magneto-optic responses. Furthermore, a mesogenic, organic molecule has been reported with a very high Verdet constant. Conclusive explanations for these large Verdet constants are still lacking, but different possible hypotheses were proposed. In our ongoing search for organic materials with exceptional magneto-optical properties, we examined conjugated, rod-like molecules. Structural, these molecules show close resemblances with the earlier reported mesogenic, organic molecule. We measured giant Verdet constants for thin films of these molecules, reaching values almost as giant as the previous reported mesogenic molecule. These findings shed first preliminary light on a structure-activity relationship for giant Faraday rotation in diamagnetic organic materials.

This work presents different polymer diffusing films for optical components. In optical applications it is sometimes important to have a film with an adjusted refractive index, scattering properties and a low surface roughness. These diffusing films can be used to increase the efficiency of optical components like organic light emitting diodes (OLEDs). In this study three different epoxy acrylate mixtures containing Syntholux 291 EA, bisphenol a glycerolate dimethacrylate, Sartomer SR 348 L are characterized and optimized with different additives. The adjustable refractive index of the material is achieved with a chemical doping by 9-vinylcarbazole. Titanium nanoparticles in the mixtures generate light scattering and increase the refractive index additionally. To prevent sedimentation and agglomeration of these nanoparticles, a stabilization agent [2-(2-methoxyethoxy)ethoxy]acetic acid is added to the mixture. Other ingredients are a UV-starter and thermal starter for the radical polymerization. A high power stirrer (ultraturrax) is used to mix and disperse all chemical substances together to a homogenous mixture. The viscosity behavior of the mixtures is an important property for the selection of the production method and gets characterized.

After the mixing, the monomer mixture is applied on glass substrates by blade coating or screen printing.

To initiate the chain growing (polymerization) the produced films are irradiated for 10 minutes long with UV light (UV LED Spot Hönle, 405 nm). After this step a final post bake from the layers in the oven (150°C, 30 min.) is operated.

Light transmission measurements (UV-Vis) of the polymer matrix and roughness measurements complement the characterization.

Main optical, thermal and mechanical properties of new compositions based on alicyclic polyimide and active bright red 6C synthetic dye have been studied. It was shown that the transmission ratio of the new material in the region of 400-900 nm and 2.0 wt.% dye concentration was around 60-70%. Thermal, mechanical and electrical properties of new colored compositions were comparable with the properties of original polyimide.

Bulk, transparent organic nonlinear optical (NLO) single-crystals of imidazolium L-Ascorbate (ImLA) were grown using slow-evaporation. Crystal structure was determined by single crystal X-ray diffraction analysis. Preliminary linear optical measurements through UV-Visible and infrared spectroscopy revealed good optical transmittance and a low near-UV cutoff wavelength at 256 nm. Kurtz and Perry powder test revealed that ImLA is a phase-matchable NLO material with a second harmonic generation (SHG) efficiency of 1.2 times larger than that of standard KH₂PO₄ (KDP). Laser damage thresholds were determined for ImLA.