The intensity dependent index of refraction and themolecular two-photon absorptivity (TPA) of 3,3'-dielthylthia-cyanine iodide (DETCI) has been measued in a range of solvents by the femtosecond z-scan technique. In DMSO, where DETCI is quite soluble, both the two-photon absorptivity and the nonlinear index of refraction are linear functions of concentration. In contrast, the two photon absorptivity and non-olniear index change of DETCI in MeOH is an order of magnitude lower and shows signs of saturation at concentrations well below the saturation limit. In high index solvents such as MeOH, the TPA of DETCI is much smaller in lower index solvents such as DMSO. The intensity dependent index chagne, n₂ is large and relatively insensitive to the index of the solvent.

Sum rules have been shown to impose a fundamental limit on the off-resonant nonlinear-optical susceptibility. We review this work, which was applied to determining the off-resonant limits, and show that sum rules can also be used to impose limits on resonance. Two-photon absorption is used as an example.

Vibrational relaxation in excited states of all-trans-carotenoids has been investigated using femtosecond stimulated Raman spectrosocpy with resolutions of 250 fs and 25 cm^-1. The initially photoexcited 1B⁺_u state in carotenoids relaxes to the 2A^-_g excited state within 1 ps. The 1B^-_u excited state is an intermediate state of the relaxation. After the relaxation to the 1A^-_g state, the excess energy is held in a C=C stretching mode (ν1) and remains longer than several picoseconds in short (mini) carotenes. Vibrational feature of carotenoids is of importance in energy transfer of phtoosynthesis. Femtosecond time-resolved vibrational spectroscopy is necessary to investigate the initial ultrafast kinetics.

Mach-Zehnder interferometric technique for nonlinearity measurements is briefly described. The optical setup is combined to a charge-coupled device image processing and allows to resolve the spatial profile of the complex nonlinear variation index with only one laser shot in the nonlinear material. Our experimental results in chalcogenide glasses clearly demonstrate the existence of an intensity dependent change of the sign in the nonlinear dephasing. It is shown that the nonlinear index coefficient cannot be correctly described with the usual cubic model. A more convenient theory is developed assuming a medium with two-photon nonlinear absorption and both cubic (n₂) and quintic (n₄) nonlinear index variations. The resulting closed-form expression for the effective nonlinear index allows to extract the cubic and quintic index coefficients.

Salicylidene-aniline (SA) derivatives have been synthesized and characterized for optical and nonlinear optical properties. The substituents used as methyl (-CH₃), chloro (-Cl), and nitro (-NO₂) groups. These substituent groups show a variation in their electro-negativity characteristics and hence have the capacity to perturb the electrons system in the parent ring structure of the salicylidene-aniline compound. Material characterization has been done using various analytical tools namely: DSC, FTIR, UV-VIS and GC/MS. The nonlinear optical characterization has been done using the Kurtz powder efficiency method. The nonlinear refractive index and the third order susceptibility have been determined using the Z-Scan method in solution using ethanol as the solvent. The Kurtz powder efficiency measurements using urea as standard gives the values as 0.7 for 3-Cl SA, 0.8 3-NO₂ SA and 1.0 for the 3-CH₃ SA derivative. The results of single bulk crystals grown using the Bridgman-Stockbarger method are reported.

The first hyperpolarizability (HP) of ullerene on the silica substructure, modeled by β-quartz layers, is calculated in the framework of the semi-empirical version of the time-dependent Hartree-Fock theory. The induced by the substrate orthogonal to the surface component of β-vector invariant is of the same order as in the 'push-pull' organic molecules with the expressed nonlinear optical properties. Just this component is responsible for generation of the second harmonic according to Hoshi and coauthors.

There are a number of organic, inorganic, and hybrid inorganic waveguide materials that are currently being used for a wide variety of optical interconnect applications. Depending upon the approach, waveguide formation is performed using a combination of lithographic and/or reactive ion etch (RIE) techniques. Often the processes involved with waveguide formation require unique processing conditions, hazardous process chemicals, and specialized pieces of capital equipment. In addition, many of the materials have been optimized for silicon substrates but are not compatible with printed wire board (PWB) substrates and processes. We have developed compositions and processes suitable for the creation of optical, planar waveguides on both silicon and PWB substrates. Based on silicate technology, these compositions use lithographic techniques to define waveguides, including aqueous, alkaline development. The resulting planar waveguides take advantage of the glass-like nature of silicate chemistry wedded with the simplicity of standard lithographic processes. Attenuation at typical wavelengths has been found to compete well with the non-silicate-based technologies available today. Single-mode (SM) and multi-mode (MM) waveguides with losses ranging from 0.6 dB/cm @ 1550nm, 0.2 dB/cm @1320nm, and <0.1 @ 850nm are feasible. Composition, process, and physical properties such as optical, thermal and mechanical properties will be discussed.

Results are presented on ultra low refractive index materials that can be used as low optical loss cladding materials for high ΔN waveguides. The porous materials are made by templating and removing nano size organic particles from a matrix. Calculations are presented for the scattering from such materials both in the bulk phase and also at the core cladding interface. The optical losses in tight turning high ΔN single mode waveguides are also calculated.

These last twenty years, advanced studies in integrated optics have demonstrated the capacity to elaborate optical circuits in planar substrates. Most of the optical integrated devices are realized on glass substrate and the guide areas are usually obtained by photolithography techniques. We present here a new approach based on the use of compounds photopolymerizable in the visible range. The conditions of self written channel creation by solitonic propagation inside the bulk of the photopolymerizable formulation are analyzed. Waveguides can be self-written in photopolymerizable materials1,2 due to the dependence of their refractive index on intensity and duration of the active light. This process results from the competition between the diffraction of the incident Gaussian beam and the photopolymerization which tends to increase the refractive index where light intensity is the highest. By controlling the difference between the refractive index values of the polymerized and non polymerized zones, the beam can be self-trapped along the propagation axis giving rise to a waveguide over distances as large as 10 cm without any broadening. Such permanent waveguides can be structured by inscription of gratings and doped with a dye in a plastic cell leading to the elaboration of a completely plastic laser.

Silicones are known for their excellent performance in applications with harsh environmental conditions. They are very well known for their high temperature stability, resistance to moisture and other adverse conditions. This paper will overview key properties of siloxanes that make them attractive materials for numerous photonics device applications with emphasis on polymer waveguides. Both thermal-mechanical and optical properties will be reviewed. Testing of key optical properties of several siloxane materials, both before and after exposure to heat, humidity, and high optical flux will be discussed. Fabrication and processing for production of polymer waveguides, and the resulting polymer device performance will be shown. Finally, the high reliability of siloxane based waveguides is demonstrated by the Telcordia testing of a fully functional, packaged, Variable Optical Attenuator (VOA).

The three-dimensional structure of thin anisotropic polymer films is of great importance for many applications, such as display technology and optical data storage. We developed different methods for the accurate determination of the in-plane and the out-of-plane anisotropy of thin polymer films. The anisotropic properties are generated or modified by irradiation with polarized light at room temperature and subsequent thermal development of the liquid crystalline polymers. For the characterisation of thin films different ellipsometric methods and absorbance measurements were developed and for thick films the prism coupling method was used. The three-dimensional structure of the films and the resulting optical properties are strongly dependent on thickness and preparation of the films. The photoinduced order is generated by the photoorientation of azobenzene containing side chain polymers. This order is changed by annealing of the films in the liquid crystalline phase of the polymers. For thinner spin coated films the order after annealing is almost a prolate in-plane order. This should be caused by the initial in-plane order induced by the spin coating process. In the case of thicker films the order after annealing is homeotropic due to the interfacial order. Under certain conditions even an oblate order was found after annealing.

Fluoropolymers are viable material options for short haul fiber and planar waveguide photonic applications. This work provides the refractive index, extinction coefficient, Sellmeier coefficients, and infrared absorption for two perfluorocyclobutyl-based (PFCB) polymers. These PFCB fluoropolymers have marked themselves as alternatives to the more well known fluoropolymers based on their solution processability and broad tailorability of optical, thermal, and mechanical properties.

New insights into the relationship between film processing conditions and properties for polyimide-based systems of interest in the fabrication of optical waveguides are presented. The critical role of the rate of solvent evaporation to ensuring high-quality films is explored, as are the effects of varying the casting solution concentration, spin casting, and baking conditions. In addition to film quality, the effect of the previously mentioned processing conditions on optical properties is also described.

In this work, we investigated the transverse birefringence in PMMA-based polymer optical fiber introduced in the drawing process. We proposed a sime theoretical model that attributes the induced transverse birefringence to three major factors: quenching effect, molecular alignment, and thermal expansion mismatch. Various experiments have been designed and performed to ascertain and identify the individual contribution of the three factors. In our experiments, polymer optical fibers are drawn under varying conditions and end their transverse birefringence is measured using the interferometric microscope method. These experiments have determined the respective contributions of the three factors and produced important findings agreeable to our theoretical model: the birefringence increases with the drawing speed ratio; the quenching-induced birefringence has profile of parabolic shape which can be removed by annealing; the profile of birefringence due to thermal expansion mismatch has an abrupt change at the core-cladding interface; and the birefringence induced by molecular alignment is constant across the fiber, and the magnitude is small.

The syntheses and electrooptic properties of a family of nonlinear optical chromophores are described. Typically, these species feature an ethyne-elaborated, highly polarizable porphyrinic component, and metal polypyridyl complexes that serve as integral donor and acceptor elements. The frequency dependence of the dynamic hyperpolarizability of a wide-range of these chromophores, that vary widely with respect to their electronic structure, was determined from hyper-Rayleigh light scattering (HRS) measurements carried out at fundamental incident irradiation wavelengths (λinc) of 830, 1064, and 1300 nm. These data show that: (i) Coupled oscillator photophysics and metal-mediated cross-coupling can be exploited to elaborate high β_λ supermolecules that exhibit significant excited-state electronic communication between their respective pigment building blocks; (ii) High-stability metal polypyridyl compounds constitute an attractive alternative to electron releasing dialkyl- and diarylamino groups, the most commonly used donor moieties in a wide-range of established NLO dyes, and long-recognized to be the moiety that often limits the thermal stability of such compounds; (iii) This design strategy clearly enables ready elaboration of extraordinarily large β_λ chromophores at telecommunication-relevant wavelengths; and (iv) Multiple charge-transfer (CT) transitions within a single chromophore can be designed to have transition dipole moments of the same or opposite sign; because the sign of the resonance enhancement factor is frequency dependent, appropriate engineering of the relative contributions of these CT states at a given wavelength provides a new means to regulate the magnitude of dynamic hyperpolarizabilities.

A number of novel salts of dipolar cations containing dimethylamino electron donor and pyridinium electron acceptor groups have been prepared and studied by using various physical techniques including hyper-Rayleigh scattering and Stark spectroscopy. In addition to showing very large molecular static first hyperpolarizabilities, several of these salts exhibit pronounced bulk quadratic nonlinear optical effects. Related compounds in which the electron donor is a ruthenium(II) ammine centre have also been investigated, allowing interesting comparisons to be made between transition metal-containing and purely organic nonlinear optical chromophores.

We evaluate the theoretical potential of a series of donor-acceptor-substituted helicenes. Different synthetic approaches towards the parent tetrathia-(7)-helicene TH(7) and the formyl derivative are described. Femtosecond hyper-Rayleigh scattering (HRS) experiments as a function of amplitude modulation (AM) frequency on the parent helicene molecule have been performed. The apparent first hyperpolarizability βapp(ω) is a decreasing function of increasing AM frequency ω, due to the two-photon fluorescence (2PF) contribution. We observe, however, for the first time, also an AM frequency-dependent HRS depolarization ratio ρ(ω). For dipolar respectively octopolar chromophores, ρ for HRS and 2PF is identical (5 respectively 1.5) and, therefore, constant as the fluorescence contribution decreases. For this helicene molecule here, we now see an increase in depolarization ratio for increasing AM frequency. An accurate value for ρ is important, since it offers an indication for the symmetry of the chromophore. The limiting value for ρ(ω) at high frequencies, i.e. ρ∞ without 2PF contribution, is in agreement with the theoretical value obtained from a purely helicoidal symmetry, i.e. a helicene without electron donor or acceptor groups.

Collagen possesses a strong second order nonlinear susceptibility; when it is irradiated with intense laser light, some of the reflected and transmitted light will have twice the frequency of the incident beam, a phenomenon known as second harmonic generation (SHG). Polarization modulation of an ultra-short pulse laser beam can be used to simultaneously measure collagen fiber orientation, SHG intensity, and a parameter related to the second order non-linear susceptibility. This technique has made it possible to discriminate among patterns of fibrillar orientation in many tissues. In the present study the role that organizational complexity plays in the relationship between nonlinear optical properties and collagen structure is investigated. As a component of tissues and organs, collagen’s structure and function is inextricably intertwined with that of the many other matrix components; to what extent do these noncollagenous components affect its nonlinear properties? To answer this, we investigated SHG in two different collagenous tissues, liver and cartilage; in addition we looked at the effect of progressive pathological changes in these tissues on SHG. At the other end of the spectrum, we studied collagen organized at the minimal level of complexity necessary for SHG detection: fibrils generated from solutions containing only a single type of collagen. Data obtained from these studies suggest that collagen’s strong nonlinear susceptibility, a property no other biologically significant macromolecule shares to the same degree, may serve as more than the basis of a novel imaging device for soft tissue. Collagen’s nonlinear optical properties in conjunction with its vast capacity for self-initiated conformational change--through self-assembly, site recognition, post-translational modification, and the like -make it an attractive candidate molecule for any of several demanding engineering applications, such as nanopatterning.

We demonstrate the possibility of optically inducing the resolution of a racemic mixture of molecules. We thus measured an optical induction of optical rotation. For this, we used an all optical method based on a pump (Ar-488 nm) - probe (He-Ne-632 nm) experiment exciting a thin layer of a new chiral photoisomerizable chromophore in a PMMA matrix.

In this study, two kinds of polyimides were prepared to investigate the effects of molecular structures on the properties of corresponding waveguides. Three kinds of the diamines were used for investigating the polarizability of the bridge group on the C-H band length and their overtone bands, including 4,4’-oxydianiline (ODA), 4,4’-thiodianiline (TDA), and 4,4’-diaminodiphenylmethane (DPM). It was found that the stronger the electron-withdrawing group of the diamines moiety of the polyimides, the shorter the C-H bond length on the aromatic ring. Thus, the C-H overtone band shifted to a lower wavelength and reduced the corresponding optical loss. Therefore, the order of the normalized optical loss was PMDA/ODA > PMDA/TDA > PMDA/DPM. Photopatternable polyimides with the 3-aminopropyltriethoxysilane (APrTEOS) and methacrylic acid-2-dimethylaminoethyl ether (MDAE) as the end capping and photosensitive moieties were successfully prepared. The retardation of the film shrinkage by incorporating the silica moiety was successfully achieved. The present studies were usefully for design and processing of polymer based channel waveguides.

The motivation to investigate moderate refractive optical polymers in finite 2D photonic crystal waveguides is manyfold. Compared to high index materials like Si, GaAs and InP the optical wavelength inside the waveguide core of a moderate refractive index material is longer and the optical field confinement in most cases is weaker.

Advancement over the past decade of materials based on two-photon absorption has been phenomenal; yet, a need for greater understanding of multi-photon processes remains. Questions of design to maximize two-photon absorbance cross-sections and quantum yields have been addressed quantitatively. However, effects of the chemical environment on the absorption and emission processes in these chromophores are largely unexplored. This study presents the effects of 26 different solvents on the absorption and emission characteristics of a set of six new alkylamino-substituted styryl pyrazines. The solvatochromic comparison method is employed to derive structure-optical property relationships within this family of fluorophores, and the effects of solvent polarity, hydrogen bonding and inductive and dispersive forces are discussed. Electrostatic and transition moments are measured and their contributions to two-photon absorbance cross-sections (δTPA) are discussed. Symmetric D-π-A-π-D molecular architecture is thought to play a very important role in increasing δTPA by disrupting the degeneracy of excited states and increasing one- and two-photon transition probabilities. The coupling of strong electron donors to strong electron acceptors with symmetric D-π-A-π-D molecular architecture is shown to produce fluorophores with exceptional two-photon activities.

We added a control electrode to a phase-shifted Bragg grating filter in an electro-optic polymer waveguide to obtained voltage tunability. The waveguide grating transmission spectrum near 1.3 microns featured a 5 GHz passband with a peak transmission of 32% within a 2 nm wide, 12 dB deep blocking band. With the waveguide grating sandwiched between gold layers separated by ~10 microns, we were able to shift the transmission spectrum at a rate of 0.1 GHz/volt. Such filter tunability may be used in ultradense WDM channel selection or to compensate for detuning by environmental factors.

Degenerate four-wave mixing phase conjugation is observed in azo-dye-doped polymer optical fibers under low-power, continuous-wave laser irradiation. A maximum phase conjugate efficiency of 1% has been obtained under a power less than 3 mW for each beam inside the fiber. Phase conjugation is observed for both parallel- and orthogonally-polarized probe and pump beams. The polarization and intensity profile are verified to be preserved in the conjugate signal. The predominant phase conjugation signal is attributed to photoinduced isomerization and reorientation of azo-dye molecules.

Two second-order nonlinear optical chromophoric materials were investigated for their response to gamma-ray irradiations for doses ranging from approximately 10-104 krad(Si). Thin film polymer modulators composed of a mixture of amorphous polycarbonate and phenyltetraene [APC/CLD-1(CPW-1)] active regions with UV upper and lower UV claddings were investigated for their pre- and post-irradiation behavior. Modulator V_π insertion loss, and extinction ratio responses were examined, while a blend of salmon deoxyribonucleic acid (DNA)- hexadeCetylTriMethylAmmonium Chloride (CTMA) film samples were studied for their spectral response following irradiations over the spectral range λ=240-2600 nm. Following irradiation ranging from 9.6-104 krad(Si), the DNA/CTMA films exhibited losses in transmissivity over the spectral range λ=882-2600 nm and increased transmissivity over portions of the 240 nm < λ < 882 nm band. Data from the study also suggested that strongly poled APC/CPW-1 modulators operating at λ=1550 nm and exhibiting low V_π values were less likely to have their half-wave voltages affected by ionizing radiation. The optical insertion losses for the majority of the APC/CPW-1 irradiated mdolators were found to decrease following irradiation. Discussion of the experimental results and mechanisms believed responsible for the post-irradiation behavior and results are presented.

We present a study of Distributed Feedback (DFB) Laser emission in polymer thin films. This laser scheme permits efficient control of the stimulated emission in dye doped polymer materials. Optical feedback is provided by distributed Bragg gratings formed in the film by interference patterns from the pump beam. We report on particular features of the thin film DFB lasers. Devices are optically pumped using a Lloyd-mirror interferometer. For a given DFB grating period, the number of lasing modes depends on film thickness. Spectral content of the devices can be analyzed using planar waveguide theory. An excellent agreement between the theoretical transverse electric mode structure and the laser emission spectrum is found. We report for the first time on another scheme in which two DFB gratings are optically excited. There results a multicolor laser emission. This new scheme can interpreted in terms of a degenerate four wave mixing (DFWM) process in which the coherent interaction between pump waves in the luminescent material is monitored by laser emission.

We present the results for a 50GHz drive amplifier for use with a Mach-Zehnder modulator. The MMIC device is packaged using a flexible substrate technology to obtain compact size and broadband performance. The packaged device exhibits well-matched transmission lines on the input and output, and large gain and bandwidth. The MMIC performance is directly related to performance of the drain bias circuit.

Macromolecular systems comprised of many light-sensitive centres (the photosynthetic unit, dendrimers, and other highly symmetric multichromophore arrays) are important structures offering challenges to theoreticians and synthetic chemists alike. Here we outline novel photophysical interactions predicted and observed in such arrays. Using the tools of molecular quantum electrodynamics (QED) we present quantum amplitudes for a variety of higher-order resonance energy transfer (RET) schemes associated with well-known nonlinear optical effects such as two- and three-photon absorption. The initial analysis is extended to account for situations where the participant donor species are identical and exist in a highly symmetric environment, leading to the possible formation of excitons. It emerges from the QED theory that such excitons are closely associated with the higher-order RET processes. General results are interpreted by analyzing particular molecular architectures which offer interesting features such as rate enhancement or limitation and exciton pathway quenching. Applications in the areas of photosynthesis, molecular logic gates and low-intensity fluorescence energy transfer are predicted.

Colloidal crystals with three-dimensional periodicities in the refractive index have a photonic band gap (PBG) in which electromagnetic waves are forbidden. We present a method to fabricate stacked colloidal crystals containing a two-dimensional defect as a middle layer by combining vertical deposition method with Langmuir-Blodgett (LB) technique. The defect layer introduces an impurity mode within the optical stop band, which is observed as a defect peak (pass band) in the optical density spectrum. The dependence of the position of the impurity mode on the size of the defect layer is investigated. It is found that the defect behaved as a donor impurity, as it originates from the bottom of the conduction band. We also study the effect of the sphere size of the surrounding colloidal crystal on the position of defect model through changing the sphere size of the surrounding colloidal crystal with a fixed sphere size of the defect layer.

A novel interferometer, a Sagnac interferometer (SI), is presented for the measurement of the difference phase and amplitude spectra induced by photoexcitation with a femtosecond time resolution. The SI has a remarkable advantage of high stability owing to the common-path configuration. In order to separate the phase and amplitude changes, the optical path difference is scanned between the probe and reference pulses making the best use of polarization. This improved polarization-division Sagnac interferometer (PSI) provides a nearly sinusoidal fringe. To demonstrate PSI we examined the nonlinear phase and amplitude changes in CS₂ and a GaAs/AlGaAs quantum well (QW) structure. The sepctral feature of the nonlinear dispersion relation in QW can be explained by the blue-shift of the excitonic resonance. The time dependence of these changes is observed to be determined by the exciton lifetime. These experimental results are consistently explained from neutralization of the built-in potential inside the QW sample.

We studied linear and nonlinear optical properties of four different phthalocyanines: vanadyl and copper phthalocyanines substituted with chiral branched side chains, (S)(OMeBu)₈VOPc, (S)(OMeBu)₈CuPc; a racemic analogue (R,S)(OMeBu)₈VOPc; vanadyl phthalocyanine substituted with linear side chains, (OBu)₈VOPc. We investigate the molecule packing and their third-order nonlinear optical response in terms of chirality, planarity, and side chain structures. Molecular arrangement of (S)(OMeBu)₈VOPc in the thin films was determined to be a columnar phase with rectangular 2D crystals by X-ray diffraction studies. The thin films of (S)(OMeBu)₈VOPc diplayed CD activity. While, a chloroform solution of this compound did not show any CD. Therefore, we conclude that the CD in the films must result from the chiral aggregation of the molecules. The Χ⁽³⁾ value of the flims of (S)(OMeBu)₈VOPc was determined for 6.7×10^-11 esu by third harmonic generation at 1.907 μm and this value was larger than those of (R,S)(OMeBu)₈VOPc, (R,S)(OMeBu)₈CuPc, and (OBu)₈VOPc.

A number of dithioacetate and dithiolate mono- and dianions have been synthesized and characterized through Z-scan measurements, with some showing significant third order nonlinear optical (NLO) behavior. Tetralkylphosphonium cations were utilized in tandem with the nonlinear anions so as to minimize electrostatic interactions within the salt, consequently resulting in the materials being room temperature ionic liquids (RTILs), which have numerous advantages over typical organic-based materials. Anions composed of metal-ligand systems were also tested for NLO behavior as components of novel ionic liquid materials. These RTILs introduce a new class of materials with potential applications in optical limiting and other all-optical devices.

We report on the observations of circulations induced by a 10-mW red He-Ne laser (633-nm wavelength) in nonlinear absorbing solutions of 2,9,16,23-Tetrakis(phenylthio)-29H,31H-phthalocyanine. Two solutions were prepared with the same concentrations (approximately 1mM/L) of phthalocyanine in chlorobenzene. Polymer poly(methyl methacrylate) was added to the second solution to increase its viscosity. When the laser beam passed through a solution, the diffraction ring pattern was observed on a screen. As the power density of the laser radiation within a solution increased, more rings could be seen (up to 15 were observed). In the less viscous solution, the rings appeared squeezed from the top half, indicating the presence of convection. In the more viscous solution, however, the rings were perfectly circular. These results were confirmed visually when the fluid circulation (at about .2 rev/s) was seen with the aid of micron size alumina particles in the less viscous solution. No circulation was seen in the more viscous solution when the beam was relatively far below the meniscus. When the beam was positioned at less than .12mm below the meniscus, circulation did occur. Then, the 100mm thick layer of the less viscous solution was positioned horizontally so that the beam was focused from the bottom. An ordered set of Benard-Rayleigh convection cells was observed (for the first time, to our knowledge, without conventional heating). This opto-mechanical effect can be implemented in light driven micro-pumps and similar fluidic devices.

The strong coupling between exciton and photon modes in a conjugated polymer-based semiconductor microcavity was observed. The σ-conjugated poly(bis(p-butylphenyl)silane) (PBPS) thin films were inserted between metal and dielectric stack mirrors to form the microcavity structure. Change of the PBPS film-thickness (from 80 to 140 nm) allowed the cavity photon resonance to be tuned in the free-exciton transition. The expected anti-crossing behavior was observed at room temperature in the reflection spectra and the vacuum Rabi-splitting energy was found to be about 430 meV. This giant value is almost the same as the expectations of transfer matrix reflectivity calculations performed with optical constants (refractive index: n, extinction coefficient: k) derived from a Kramers-Kronig analysis of the PBPS absorption spectrum. Angle-dependent photoluminescence measurements were performed in each PBPS-based microcavity. In the microcavity with a 120nm-PBPS layer, the polariton emission that displays almost no blueshifts with angle was observed, a desirable feature for potential display applications.

Two types of photo-induced gratings, birefringence and surface relief gratings, were formed on an azo polymer film when two orthogonal circularly polarized writing beams irradiated the film. All the diffracted beams from the gratings were measured during irradiation and the surface relief height inscribed on the film was measured by using atomic force microscope (AFM) after the irradiation. The transmitted beam intensities were calculated using a Jones matrix for two gratings. The phase differences for the two gratings were separately determined by fitting the experimental results to the theory. Next, the changes of the phase differences of two gratings were measured in-situ using an exact equations. The results from this method agreed with previous one. The phase difference between two gratings was measured. The phase difference between two gratings converged on about 45 degrees in our case. Diffraction efficiency measurement and analysis revealed that the two gratings were independent of each other and that the mechanisms for the two gratings were different.

Transition metal carbonyl clusters incorporating group 6 (molybdenum, tungsten) and iridium atoms in a tetrahedral or butterfly-shaped four-atom cluster core, together with carbonyl, cyclopentadienyl and alkyne ligands, have been synthesized and incorporated into oligourethanes, and their optical limiting properties assessed by open-aperture Z-scan (ns pulses, 523 nm) and time-resolved pump-probe studies (ps pulses, 527 nm). The Z-scan studies reveal that the tetrahedral [M₂Ir₂] cluster cores (M = Mo, W) displayed a greater effective nonlinear absorption coefficent β₂ than the [MoIr₃] cores; the tungsten example, W₂Ir₂(CO)₁₀(η-C₅H₅)₂, exhibited the highest response. Substitution at the cyclopentadienyl group (including incorporation into a polymer backbone) had little effect on the response measured. A time-resolved investigation of the alkyne-adduct Mo₂Ir₂(μ₄-η²-MeC₂Ph)(CO)₈(η-C₅H₄Me)₂ using picosecond pulses at 527 nm reveals optical-power-limiting behaviour that results from electronic processes [specifically, a fast nonlinear absorption process followed by reverse saturable absorption involving long-lived (>1000 ps) metastable excited states].

Future generations of photonic devices which incorporate poled organic nonlinear optical materials may be aided by, or require the use of non-traditional electrodes. This report details the integration of highly doped silicon as one of the poling/modulating electrodes in the simple reflection type experiment for determination of nonlinear optical activity in a guest-host polymer system. The measurements illustrate that the behavior of doped-silicon and the traditional indium tin oxide (ITO) electrodes are analogous. A number of organic chromophore guests were investigated as well as multiple polymer hosts. Results demonstrate both successful poling and subsequent modulation of NLO materials, including the calculation of r33 values comparable to those achieved using a standard ITO electrode.

A series of complex salts in which trans-bis[1,2-phenylenebis(dimethylarsine)]chlororuthenium(II) electron donor groups are connected to pyridyl or pyridinium electron acceptors has been prepared. These chromophores exhibit intense, visible metal-to-ligand charge-transfer (MLCT) absorptions and reversible Ru(III/II) (and also in some cases ligand-based) redox processes. Stark (electroabsorption) spectroscopic studies have been used to determine dipole moment changes for the MLCT excitations. Static first hyperpolarizabilities have been calculated according to the two-state model, allowing the derivation of structure-activity correlations for the molecular quadratic nonlinear optical responses.

A series of 2,2':4,4'':4',4'''-quaterpyridinium ligands bearing different N-substituents (methyl, Me; phenyl, Ph; 4-acetylphenyl, AcPh; 2-pyrimidyl, Pym; 3,5-bis-methoxycarbonyl-phenyl, MCP) have been prepared. These compounds feature powerful electron acceptor moieties and hence have been combined with different electron-rich metal centres to give complexes suitable for quadratic nonlinear optical properties. A series of dipolar ruthenium(II) ammine complex salts of the form [Ru^II(NH₃)₄L_A][PF₆]₄ and octupolar complex salts of the form [M^II(L_A)₃][PF₆]₈ (M = Ru(II)/Fe(II), L_A = a 2,2':4,4'':4',4'''-quaterpyridinium ligand) have been prepared. These compounds exhibit multiple intense, low energy metal-to-ligand charge-transfer (MLCT) absorptions in the visible region and reversible M(III/II) redox processes. First hyperpolarizabilities have been determined directly by using hyper-Rayleigh scattering and indirectly via calculation from Stark (electroabsorption) spectroscopic data.

Thin films of the organic complex PVK:TNF were studied for various rates of TNF (0 to 50%) by means of photoinduced current transient spectroscopy (PICYS) and photoconductivity measurements. PICTS reveals the presence of a continuous trap distribution. Both the two models of the transport phenomenon by hopping (microscopic behavior) or by multiple trapping (more efficient for a quantitative explanation) explain the shape of the decay of photoconductivity and the observed results. Contrarily to amorphous semiconductors, the trap distribution is not here exponential. In a first approximation, the distribution is fairly uniform until 0.6-0.65 eV, followed by a sharp decrease until about 0.85 eV where the density of states practically vanishes. The microscopic model of hopping allow an interpretation of the distribution and gives a plausible explanation of the observed results.

Electronic structural modifications of previously reported highly conjugated (polypyridyl)metal-(porphinato)zinc(II) NLO chromophores have been carried out. A primary focus of these modifications probed the role played by the porphyrin macrocycle in effecting large molecular hyperpolarizabilities; specifically, its meso-aryl substituents were replaced with electron withdrawing perfluoroalkyl groups. In doing so, we are effectively lowering HOMO and LUMO of the porphyrin fragment by 0.35eV while retaining the extensive mixing of B, Q, and CT states, and enforcing head-to-tail transition dipole alignment of the component metal-polypyridyl and porphyrin based chromophoric building blocks; this enables supermolecular structures with singly degenerate excited states polarized along the long donor-to-acceptor (D-to-A) charge transfer axis. This work will be placed in the context of ongoing electrooptic experiments and efforts aimed at fabricating new materials from these supermolecular chromophoric species.

We present a wavelength-resolved study of the third-order nonlinearity of two derivatives of the 2-amino-1,2,3 triazole-quinone molecule. The substitution groups are a dialkylaminophenyl in one case, and ferrocene in the other, and both samples were prepared as chloroform solutions. The z-scan technique with a tunable 10 ps laser source was used to resolve the absorptive and refractive contributions to the nonlinearity at several wavelengths near resonance. In the case of the ferrocene derivative, the nonlinear response is attributed to the metal-ligand charge transfer that gives rise to the absorption spectrum features. The absorptive contribution changes from saturable to two-photon absorption going away from resonance, vanishing at λ=540 nm, while the nonlinear refractive index n₂ remains finite. This is important for possible applications based on nonlinear refractive effects. For the dialkylaminophenyl derivative, a complex combination of saturable and induced absorption is observed at several wavelengths, becoming induced absorption closer to resonance and weak saturable absorption away from resonance. For both samples the nonlinear refractive index remains positive throughout the spectral range investigated.