This PDF file contains the front matter associated with SPIE Proceedings Volume 8113, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Photorefractive composites derived from conducting polymers offer the advantage of dynamically recording holograms without the need for processing of any kind. Thus, they are the material of choice for many cutting edge applications, such as updatable three-dimensional (3D) displays and 3D telepresence. Using photorefractive polymers, 3D images or holograms can be seen with the unassisted eye and are very similar to how humans see the actual environment surrounding them. Absence of a large-area and dynamically updatable holographic recording medium has prevented realization of the concept. The development of a novel nonlinear optical chromophore doped photoconductive polymer composite as the recording medium for a refreshable holographic display is discussed. Further improvements in the polymer composites could bring applications in telemedicine, advertising, updatable 3D maps and entertainment.

Silica optical microcavities experience linewidth broadening and resonant frequency instability as a result of their high Q factors. One of the causes is the thermo-optic effect or temperature induced changes in refractive index. For many telecommunications and biodetection applications, it is critical to have a stable, temperature independent, resonant frequency. In this research, silica microtoroid resonators are coated with two different polymers: polymethylmethacrylate (PMMA) and polystyrene (PS). The hybrid device has minimal thermal response with proper film thicknesses depending on the polymers because the positive dn/dT of silica is balanced by the negative dn/dT of the polymer. The results follow theoretical predictions based on finite element method simulations.

We review our recent advances in two-photon induced photochemistry to fabricate three-dimensional micro-objects made in polymers, proteins and noble metals using Q-switched Nd:YAG microchip lasers. We have synthesized a new photoinitiator that is about 4 times more sensitive for two-photon polymerisation with sub-nanosecond pulses at 532 nm. We describe the improvement of our fabrication process and strategies to obtain solid microstructures that correspond to their models. We report on our progress to make silver microstructures by the photoreduction of silver nitrate with microchip lasers at 1064nm.

We summarize here studies aimed at incorporating silver nanoparticles or semiconductor nanoparticles (quantum dots) into polymeric microstructures. Two different approaches are followed in the case of silver nanoparticles and quantum dots (QDs). In case of silver a combination of photoreduction and thermal annealing are adapted. This combination is used to reduce a silver salt precursor to generate silver nanoparticles inside a photopolymerizable resin. Quantum dots were functionalized with photocrosslinkable ligands to enable their easy integration into a photopatternable resin.

The role played by surface plasmon in metal NPs-dye interaction is discussed. Importance of the optical spacer is addressed based on time resolved photoluminescence experiments. The potential application of metal NPs surface plasmon to organic light emitting diodes is highlighted.

In this study, we developed a novel strain measurement technique for electrochemically aligned collagen (ELAC) fibres using second harmonic generation (SHG) microscopy. The ELAC fibres were prepared by a typical electrochemical method and were subjected to cross-linking. For comparison with natural collagen fibres, polarization dependency of the prepared ELAC fibres and that of a human Achilles' tendon were evaluated. The results showed that, because of crosslinking, the ELAC fibres exhibit polarization dependency similar to that of the tendon but only in a region close to the tendon. The relationship between SHG and the applied strain was determined by a combination of SHG microscopy and tensile tests. The SHG from the ELAC fibres changed in the high strain region because of the applied stress.

In the quest for organic second-order nonlinear materials, self-assembled structures based on octupolar molecules have shown to be promising candidates. The presented work focuses on an octupolar substituted 1,3,5-trisalkynylbenzene that forms crystals that show significant second-harmonic generation (SHG). Continuous polarization SHG measurements were performed to elucidate the tensorial nature of this response. Unfortunately the model at hand was unable to fit the polarization patterns due to depolarization of the second harmonic beam caused by multiple scattering in the sample. Although the chromophore is clearly achiral, these patterns revealed a different response for left and right circularly polarized light, also known as SHG circular difference. This implies that these molecules spontaneously assemble in chiral superstructures. These surprising results were confirmed by circular dichroism spectroscopy, revealing a monosignate CD band that must be attributed to a supramolecular chiral organization.

The effect of extending the conjugation length, the deployment of various substituents and configurational locking of the polyene backbone on the second-order nonlinear optical (NLO) response of a series of indoline based compounds has been investigated. The compounds were examined using Hyper-Rayleigh scattering (HRS) and relative second-harmonic generation (SHG) techniques with a femtosecond operating system with a 1300 nm fundamental wavelength. All of the compounds were found to have high molecular hyperpolarizabilities with β values of up to 1230 × 10^-30 esu. At the macroscopic level-for poled polymer thin films-a strong second-order NLO signal has been detected and d₃₃ values of up to 217 pm/V are found-a response of some ten times greater than that found for the well known azo dye Disperse Red 1.

We present a setup to measure the nonreciprocal magneto-optical phase shift in air and polymer cladded silicon on insulator waveguides. A high sensitivity could be achieved for the setup sufficient to determine the effect produced by silicon and silica. A silicon waveguide covered with a Fe₃O₄ nanoparticle containing polymer shows an amplitude modulation resulting from Faraday ellipticity which is of the same order of magnitude as the Faraday effect in silicon. We further present the theoretical concept of an optical isolator based on resonance splitting in a silicon ring resonator covered with a magneto-optical polymer cladding. A polymer magneto-optical cladding causing a 0.01 amplitude of the offdiagonal element of the dielectric tensor is assumed. It is shown that the derived resonance splitting of the clockwise and counterclockwise modes increases for smaller ring radii. For the ring with a radius of approximately 1.5 μm, a 29 GHz splitting is demonstrated. An integrated optical isolator with a 10μm geometrical footprint is proposed based on a critically coupled ring resonator.

Nonlinear optical transmission in materials has several applications including laser mode-locking, pulse shaping, optical bistability, optical switching, and optical power limiting. Organic molecules suitable for functionalization have been extensively investigated for their third order nonlinearities. We have measured the optical nonlinearity of different novel organic and composite systems including nanocomposite polymer films of Au, Ag and Pt, Organic ionic crystals (pyridinium and quinolinium salts), Au-alkanethiol clusters, thiophene based polymers, and Schiff base complexes, using the z-scan and degenerate four wave mixing techniques, employing laser pulses of nanosecond and femtosecond durations respectively. Most of these materials are found to be efficient optical power limiters under our excitation conditions, and their nonlinear extinction coefficients have been calculated. Enhancement in the optical nonlinearity was sometimes obtained even by mixing of two organic media. From degenerate four wave mixing experiments, the third order nonlinear susceptibility χ⁽³⁾ and figure of merit χ⁽³⁾/α values also have been determined for some of these materials. The above experiments conducted in a large number of organic and composite materials unravel the potential of these media for diverse photonic applications.

The use of a two-level approximation to simply characterize the nonlinear optical properties of organic materials is well known. Usually only electronic ground states are significantly populated; higher levels are engaged only in the capacity of virtual states, and it is frequently assumed that just one such state dominates in determining the response. Calculating nonlinear optical susceptibilities on this basis, excluding all but the ground and one excited state in a sum-over-states formulation, is a technique widely deployed in the calculation and analysis of nonlinear optical properties. However, the necessity for such an approach is diminishing as, particularly within the last decade, the accuracy of ab initio calculations has reached unprecedented levels. This offers new opportunities for a vigorous test of existing models using real molecular structures. Here we report the results of our recent work on testing the general validity of two-level calculations in nonlinear optics. Firstly, through the extension of approximation to a three-level model we demonstrate that the neglect of additional excited states can lead to substantially erroneous results for the hyperpolarizability elements. Secondly, using high levels of theory and basis set we report the results of ab initio calculations for both ground and electronically excited states of the optimised structures, for selected merocyanine dyes. The results are used for the calculation of hyperpolarizabilities by a rigorous sum-over-states formulation. A systematic comparison with the two-level approach provides a means for identifying the limits of the model and the criteria for its validity.

Traditionally, the nonlinear optical response at the molecular level has been modeled using the two-level approximation, under the assumption that the behavior of the exact sum-over-states (SOS) expressions for the molecular polarizabilities is well represented by the contribution of only two levels. We show how, a rigorous application of the Thomas-Kuhn sum-rules over the SOS expression for the diagonal component of the first-hyperpolarziability proves that the two-level approximation is unphysical. In addition, we indicate how the contributions of potentially infinite number of states to the SOS expressions for the first-hyperpolarizability are well represented by the contributions of a generic three-level system. This explains why the analysis of the three-level model in conjugation with the sum rules has lead to successful paradigms for the optimization of organic chromophores.

Quantum-confined systems, such as quantum wires, have attracted attention because their nonlinear optical (NLO) properties are enhanced due to confinement effects. In the present work, we have developed a method to study what other factors may affect the NLO properties of such systems. For this purpose, we develop a model system that eliminates confinement effect contributions to the NLO properties. We test the validity of our model by verifying that the sum rules, which are a direct consequence of quantum mechanics, are obeyed. This allows us to focus on how the NLO response of a quantum wire depends on parameters such as the geometry and topology of quantum loops, which are built from networks of quantum wires.

We review our work on nanopatterning in azo-polymer films by single, two- and multi-phopton driven molecular motion in solid bulk polymer. It is now known that light induced molecular movement occurs below the polymer glass transition temperature by chromophores photoisomerization via either linear or nonlinear absorption, and in this paper we will show that nanoscale polymer movement is induced by a tightly focused laser beam in an azo-polymer film just at the diffraction limit of light. The deformation pattern which is produced by photoisomerization of the azo dye is strongly dependent on the incident laser polarization and the longitudinal focus position of the laser beam along the optical axis. The anisotropic nanofluidity of the polymer film and the optical gradient force played important roles in the light induced polymer movement. We explored the limits of the size of the photo-induced deformation, and we found that the deformation depends on the laser intensity and the exposure time. The smallest deformation size achieved was 200 nm in full width of half maximum; a value which is nearly equal to the size of the diffraction limited laser spot. Furthermore, a nano protrusion was optically induced on the surface of the films, beyond the limit of light diffraction, by metal tip enhanced near-filed illumination. A silver coated tip was located inside the diffraction limited spot of a focused laser beam (460 nm), and an enhanced near-field, with 30 nm light spot, was generated in the vicinity of the tip due to localized surface plasmons. The incident light intensity was carefully regulated to induce surface nanodeformation by such a near-field spot. A nano protrusion with 47 nm full width of half maximum and 7 nm height was induced. The protrusion occurs because the film is attracted towards the tip end during irradiation. At the top of the protrusion, an anisotropic nanomovement of the polymer occurs in a direction nearly parallel to the polarization of the incident light, and suggests the existence at the tip end of not only a longitudinal, i.e., along the tip long axis, but also a lateral component of the electric field of light. The azo-polymer film helps map the electric field in the close vicinity of the tip. We also report on two-photon patterning of the films. Exposure of azo polymer films, which absorb in the visible range (λ_max = 480 nm), to intense 920 nm irradiation leads to polarization dependent patterning which are associated with polymer nanomovement caused by photoselective two-photon cis ↔ trans isomerization, while irradiation at 780 nm induces multi-photon bleaching of the azo chromophore. These wavelengths hit bleaching and isomerization pathways in the chromophore, respectively.

Third-order nonlinear optical properties of three isomeric tetrapyrrole triads, i.e. mixed (porphyrinato)(phthalocyaninato) yttrium double-decker complexes appended with one metal free porphyrin chromophore at the para, meta, and orthoposition, respectively, of one meso-phenyl group of the porphyrin ligand in the double-decker unit through ester linkage, 3-5, were comparatively investigated along with the model compounds metal free meso-tetrakis(4-tert-butylphenyl) porphyrin H₂TBPP (1) and mixed [meso-tetrakis(4-tert-butylphenyl)porphyrinato] [1,4,8,11,15,18,22,25-octakis(butyloxyl)phthalocyaninato] yttrium double-decker complex Y^IIIH(TBPP) [Pc(α-OC₄H₉)₈] (2) by using Z-scan technique with the fundamental (800 nm) laser emission from a Ti:sapphire femtosecond laser system. Strong reverse saturable absorption (RSA) properties of complexes 2-5 were observed. Interestingly, under highly intense irradiation, an RSA-SA-RSA-SA-RSA switch behavior was evolved in the tight focal intensity regime on the Z-scan profiles of complexes 3-5. Under the laser irradiation with focal intensity of 7.48-8.39 GW.cm_-2, the triads 3 and 4 with the metal free porphyrin chromophore appended at the para or meta positions of the meso-phenyl group of the porphyrin ligand in the double-decker unit retained a characteristic response of RSA. In contrast, the triad 5 with the metal free porphyrin chromophore appended at the ortho position has already shown a trend of SA peaks at the same intensity range, revealing the effect of the position of porphyrin-substituent on the nonlinear optical properties of the triads.

We present a simple Monte Carlo modeling of the light-driven expansion in a host-guest system polymer - azodye, which is the main mechanism responsible for the photomechanical effect in a dye-doped polymer fiber illuminated with linearly polarized laser light. Bond-fluctuating model of polymer matrix is used, the concept of void - free volume in the matrix - is quantified. The role of the dyes which are in trans state oriented along the beam propagation direction in the elongation of the system is studied via a non-thermal kinetic Monte Carlo process. Preliminary results show that upon illumination the system expands while in the dark period it shrinks.

Photochromic polymer materials with large modulation of properties enable the production of functional optical devices. The light-triggered change in color has been exploited to develop multi-object focal plane masks for astronomical instrumentation and holographic optical elements for interferometric optical testing. Modulation of properties other than color (i.e. refractive index, light emission or Raman scattering) opens the way to many other applications into technology, such as rewritable optical memories, switchable organic lasers, etc. In this background, examples from molecular design to devices are highlighted.

The continued interest in molecules that possess large quadratic nonlinear optical (NLO) properties has motivated considerable interplay between molecular synthesis and theory. The screening of viable candidates for NLO applications has been a tedious work, much helped by the advent of the hyper-Rayleigh scattering (HRS) technique. The downside of this technique is the low efficiency, which usually means that measurements have to be performed at wavelengths that are close to the molecular resonances, in the visible area. This means generally that one has to extrapolate the results from HRS characterization to the longer wavelengths that are useful for applications. Such extrapolation is far from trivial and the classic 2-level model can only be used for the most straightforward single charge-transfer chromophores. An alternative is the TKSSOS technique, which uses a few input-hyperpolarizabilities and UV-Vis absorption data to calculate the entire hyperpolarizability spectrum. We have applied this TKS-SOS technique on a set of porphyrines to calculate the hyperpolarizability dispersion. We have also built a tunable HRS set up, capable of determining hyperpolarizabilities in the near infrared (up to 1600 nm). This has allowed us to directly confirm the results predicted in the application region. Due to the very sharp transitions in the hyperpolarizability dispersion, the calculation is subjected to a very precise calibration with respect to the input-hyperpolarizabilities, resulting in very accurate predictions for long wavelength hyperpolarizabilities. Our results not only underscribe the aforementioned technique, but also confirm the use of porphyrines as powerful moieties in NLO applications.

Nonlinear optical properties of a series of protonated mixed (porphyrinato)(phthalocyaninato) rare-earth double-decker complexes [M^IIIH(TClPP){Pc(α-OC4H9)8}] (1-6; M = Sm, Eu, Tb, Y, Ho, Lu; TClPP = meso-tetrakis (4-chlorophenyl)porphyrinate; Pc(α-OC4H9)8 = 1,4,8,11,15,18,22,25-octakis(1-butyloxy)phthalocyaninate) in dichloromethane were studied by using Z-scan technique with the fundamental laser emission at 800 nm from a Ti:sapphire femtosecond laser system under different incident laser intensities. All these complexes showed strong reverse saturable absorption related to the excited singlet population in a simple three-energy-level model which was established for the interpretation of the experimental results. Both the linear and effective nonlinear absorption coefficients of these complexes decreased approximately following the ionic radius contraction sequence of the rareearth( III) cations within these complexes under the same situations. The effective excited-state absorption cross sections were determined as well.

We report the results of measurements performed on a particular platinum(II) 4,4'-bis[3-ethyl-1-(2-ethylhexyl)heptyl]-2,2'-bipyridyl complex bearing 2-(benzothiazol-2'-yl)-7-ethynyl-9,9-dihexadecyl-fluorenyl units. A similar complex, identical except for the presence of ethyl groups at the 9-position of the fluorenes and tert-butyl groups at the 4- and 4'- positions of the bipyridine, was recently reported to possess a very high ratio of triplet excited-state absorption to ground-state absorption, a quantity that has long been used as a figure of merit for reverse saturable absorbers; in addition, femtosecond transient difference absorption experiments and picosecond open-aperture Z-scans have shown it to display broad nonlinear absorption throughout the visible spectrum. In this work, we measured the triplet excitedstate absorption cross section at several representative wavelengths between 450 nanometers and 660 nanometers in an open-aperture top-hat Z-scan experiment employing a nanosecond-pulsed tunable optical parametric oscillator (OPO). The open-aperture Z-scan is a highly sensitive single-beam experiment used to measure nonlinear absorption. Since the spatial profile of the OPO beam resembled a cross-pattern, we closed an adjustable iris on the beam to create a top-hat profile. A dynamic five-level model was used to fit the Z-scan data.

In given study a new structural design of molecular NLO materials is presented where amorphous phase formation is achieved by introduction of bulky trityl and triphenylsilyl substituents. Obtained materials formed stable organic glasses with good optical quality and glass transition temperatures notably exceeding ambient. NLO activity was successfully measured in samples that underwent corona discharge poling. The comparison of both enhancer groups revealed, that trityl group increases thermal sustainability of material, while triphenylsilyl group better promotes formation and stability of amorphous phase.

Recently a melt-processed blend of 1,4-bis(α-cyano-4-octadecyloxystyryl)-2,5-dimethoxybenzene (C18-RG) dye and polyethylene terephthalate glycol (PETG) has been demonstrated as a promising 3-dimentional optical data storage (ODS) medium 1. ODS in this novel system relies on the laser-induced switching of the aggregation state of the excimerforming fluorescent dye in the inert host polymer. Here we investigate the mechanism and the time scales involved in the writing process. The optical writing was realized by the laser-induced localized excimer to monomer conversion and was characterized by the emergence of the monomer fluorescence. We obtained the dependence of the excimer to monomer conversion on the writing time. Our result indicates that the effective optical writing time is controlled by heating and cooling time of the host polymer and the excimer-to-monomer conversion time. The effective laser writing time, under the specific writing conditions employed in our experiments, is on the order of 10 ms.

In the second order nonlinear (NLO) optics, interchromophore electrostatic interactions have been suggested as a major challenge of the poor efficiency in the poling induced polar order. In this article, we formed a β-cyclodextrinchromophore inclusion compound by embedding a dumb-bell shape chromophore in a β-cyclodextrin. Compared to hyperbranched chromophores, this inclusion compound could create a 360° steric hindrance and pull the distance between molecules. Then this inclusion compound could prevent chromophore aggregation and minimize the interactions which hamper higher nonlinear optical activity. The method of the refractive index for electro-optic materials which can determine the degree of chromophore aggregation in polymers was first proposed and confirmed in this work. These properties have provided a great promise in the fabrication of EO materials and devices.