The synthesis and first hyperpolarizabilities (β) of various donor-acceptor substituted thiophene containing compounds with extended conjugation are reported. Results indicate that replacing phenyl rings with less aromatic thiophene moieties enhances the second-order hyperpolarizability. Incorporating the acceptor group, N,N' diethylthiobarbituric acid, that can gain aromaticity upon charge-separation has also led to an increase in the nonlinearity. Some of the molecules have been incorporated into poIy (Methyl Methacrylate) and the electro-optic coefficients of these host-guest polymers were Measured.

Photonic polymers and devices with improved performances are reported. Optical losses in electro-opic polymers below 0.5 dB/cm at 1.3 and 1.6 μm have been realized. IMprovements in thermal stability have led to poled polymers exhibiting a relaxation time of 1 12 days at 125°C. The thermo-optic switches reported here are close to the requirements in telecommunications, and electro-optic devices with low switching voltages and high extinction coefficients are described as well.

The relaxation of the nonlinear optical coefficient of poled electro-optic polymers remains an important issue in the potential application of these Materials. This relaxation is due to the homogenization of the orientational distribution function of nonlinear chromophores in the polymer glass over time. We have measured the relaxation using optical second harmonic generation as a function of temperature for doped polymer materials over a range of temperatures deep in the glassy state. We relate the data to widely used physical models of the glassy state which indicate that the relaxation process occurs over a considerable range of time scales. It has been found that the decay of the nonlinear polarization exhibits two mechanisms depending on the time and temperature scales over which measurements are performed. We have carried out measurements over a range of times and show that a broad distribution of relaxation times characterizes the data. This broad distribution is an appealing model in that it not only fits the data well, but is well connected to accepted physical models of the relaxation behavior of glasses. The characteristic energy of the relaxation can be estimated from the temperature dependence and is found to be equal to or less than the energy characterizing the polymer Motion, and agrees with dielectric studies. This indicates that the chromophores are more or less coupled to the dynamics of the polymer chain. A figure of merit for the coupling of the chromophore to the polymer chain is proposed.

Buried channel wave guides have been fabricated from thermally stable non linear optical polyimides. The Material system consists of a polyimide cladding and a polyimide based active Material. The buried channel wave guides are fabricated by a trench and fill process. This process was used for the fabrication of active wave guides at process temperatures above 300 °C. Single Mode wave guides, and Mach-Zenhder interferometers, were fabricated with attenuation < 2 dB/cm. Active Mach-Zehnder interferometers with a Vπ phase shift of 50 volts and the low attenuation were fabricated. Thermal aging of the poled active device demonstrated no change in activity after 30 Minutes at 230°C.

A new synthetic method is developed to incorporate efficient nonlinear optical chromophores containing thiophene conjugating units and tricyanovinyl acceptors into side-chain polymers. This approach emphasizes the incorporation of the tricyanovinyl groups into the pendant side chains after the desired polymer is formed.

A new class of high thermal stability fused-ring guest chromophores intended for incorporation into highly stable host polyimides has been successfully developed. Thermal stabilities far in excess of 300°C have been achieved for both the pure guest and the guest-host polyimide systems. The Microscopic second order nonlinear optical properties of the guest chromophores have been characterized both theoretically and experimentally. The achievement of the new high temperature EO chromorphores and polyimide formulations have directly resulted in the discovery of new EO device designs and architectures.

Second-order nonlinear optical polymers can be divided into four groups regarding arrangements of chromophore dipoles in polymer backbones, namely, side-chain polymers, random, head-to-tail, and head-to-head Main-chain polymers. A variety of polymers with the aforementioned configurations have been designed and synthesized from functionalized amino-nitro azobenzene chromophores. Poling processes of these polymeric materials have been investigated by in-situ poling and second-harmonic generation detection.

We have synthesized a new second-order NLO compound containing both the highly active tricyanovinyl electron acceptor group and appropriate funtionality for covalent bonding to an inorganic silica matrix by sol-gel processing. Sub-Micron films of this material can be prepared by spin-coating, and thicker films can be prepared by casting or by spinning multiple layers. After curing at 150 °C, these films exhibit good chemical durability. The chromophores can be aligned by either corona or parallel-plate poling during the curing process. In this paper we will discuss the synthesis of the NLO compounds; sol-gel processing and thin-film preparation; optical, thermal, and chemical properties of the films; and the results of both corona and parallel-plate poling experiments.

A new class of IPN system has been prepared and investigated. This IPN system combines the polybismaleinimide network and the NLO-active phenoxysilicon network. The second-order NLO coefficients, d33, values of the samples range from 2.5 to 6.7 pm/V depending on the composition and the processing conditions. The temporal stability of the second-order nonlinearities for these samples at 110 °C varies from 47 to 88 % retention after 274 h.

A new class of high temperature polymeric materials capable of second order nonlinear optical effects has been developed and characterized. These polymers, Bisphenol A-poly (arylene ether) phosphine oxides (Bis A-PEPO), F6 Bis A-PEPO, phenolphthalein•PEPO (PP-PEPO), and phenolphthaIein-anilide•PEPO (PP-PEPO), doped with nonlinear optical chromophores are being examined using second harmonic generation. Corona poling is used to orient the chromophores into the noncentrosymmetric structure required to obtain the second harmonic signal. These high glass transition temperature (>200°C) polymers have strong hydrogen bonding sites that can interact with the chromophores. This work describes the basic polymer physics including local Mobility, chromophore/polymer interactions, and polymer steric effects that control the thermal and temporal stability of chromophore orientation in these guest-host polymeric systems.

Electro-optic polymers are of great interest for inserting photonic elements into electronic systems. Recently Much progress has been made in both materials and processing. These polymers must have low optical loss, high mechanical integrity, low processing cost, and high temperature stability. In the first part of our talk, we present our work to produce etched single mode buried channel waveguides in an all polymide system. We have chosen polyimide because of its high temperature stability. Optical losses and waveguide characteristics are described as a function of waveguide width and index ofrefraction difference between core and cladding.

Mach Zehnder Modulators fabricated using a DCM-polymide core are also described The waveguide cores are etched and fully embedded in a polyimide cladding. The active arms of the modulator are poled using parallel plate poling. The electro-optic properties of the Mach Zehnder are described operating at 830nm. Photobleached DCM waveguides are also describe. A new high temperature chromophore is presented.

In this paper some of the more important Hyper Rayleigh Scattering (HRS) Measurements performed in our laboratory are reviewed. The results of experiments conducted on polymers, the protein Bacteriorhodopsin, retinal derivatives and octopoles are presented. Basic HRS theory, along with a brief description of the HRS set-up, is also included.

We demonstrate that the experimental simplicity of HRS allows for an accurate determination of the first hyperpolarizability of molecules that could not have been measured by the more traditional Electric Field Induced Second Harmonic Generation (EFISHG) technique.

The photorefractive properties of photoconducting polymers doped with nonlinear azo dyes are investigated by means of polarization and field-dependent four-wave Mixing experiments. The nonlocal response of the photorefractive effect is shown by two-beam coupling experiments. High diffraction efficiencies (> 5%) and net coupling gain (6 cm-l) are demonstrated at low power with a semiconductor laser diode in 105 μm films. Under some conditions, gratings due to photoisomerization of the azo dye molecules are also present and their properties are discussed.

A new class of organic sol-gel second-order nonlinear optical (NLO) Materials based on hexa (Methoxymethyl) Melamine has been investigated. NLO active chromophores, 4- (4′-nitrophenylazo) aniline and 4-amino-4′-nitrobiphenyl, were incorporated into the Melamine Matrices. Samples exhibit second-order optical nonlinearity after poling and curing at 220 °C for 30 Min. The synthesis, preparation, and characterization of these materials are reported.

Poly (arylene ether)s can be designed to be amorphous, optically clear materials with excellent hydrolytic and thermal stability as well as good electrical, Mechanical and fire resistant properties. As a result, the use of these macromolecules in second order nonlinear optical (NLO) applications are being investigated. Typically, polymeric systems with doped chromophores result in a signigicant decrease in Tg. Methods were investigated to functionalize the polymer backbone with NLO chromophores, resulting in increased Tg.

Much effort has been put into improving the temporal stability of electric field-induced chromophore alignment in molecularly doped or functionalized polymers for second order nonlinear optical device applications. Characterization of the alignment decay in electric field-poled films is complicated by charge injection during poling. In order to optimize poling schemes and to accurately determine the orientational mobility of the chromophores it is necessary to develop methods to measure the spatial extent and time-dependence of any residual fields in the polymer films. Such Measurements will also be important for the development of polymer-based electro-optic devices, and in fact for any guided wave application in these materials since the residual field may induce a spatial dependence in the refractive index.

A new second-order nonlinear optical organic Material, 8-(4′-acetylphenyl)-l,4-dioxa-8-azaspiro[4.5]decane (APDA) was synthesized as a frequency doubler emitting blue light. Its crystal growth, linear and non-linear optical properties were evaluated. The APDA crystal has a short cutoff wavelength of 384 nm and high nonlinear optical coefficients d33=50 pm/V and d32=7 pm/V. The crystal is phase matchable below wavelengths of 800nm, and its maximum effective nonlinear coefficient is 14.9 pm/V. Type I phase-Matched second harmonic generations can be carried out with YAG and Ti-sapphire laser pumping.

We have investigated intercalation into optically transparent MPS3 (M = Mn, Cd) phases as a way towards spontaneous poling of cationic chromophores. Two nano-composite Materials of formula M0.86PS3 (dimethylamino-N-Methyl stilbazolium)0.28 were synthezised, and an efficiency up to 750 times that of urea was recorded in the cadmium intercalate. An additional interest arises from the possibility to associate NLO properties with the magnetization of the host lattice in the case of MnPS3 below 40 K.

We investigate the pretransitional behavior in laser-induced alignment of rigid rod-like polytetraflouroethylene (PTFE) suspensions. Using a laser-induced birefringence experiment, we measure both the orientational order parameter and the orientational relaxation time. We find that both increase as the volume fraction of colloidal particles approaches the critical value for the isotropic-nematic phase transition. Experimental results are compared with theory which takes into account the possibility of a first-order phase transition induced by a laser electric field.

A review is presented describing our recent work to correlate the first hyperpolarizability, β, of organic materials with the molecular parameter bond length alternation (BLA). Donor-acceptor polyenes displaying a wide BLA range were synthesized. For a particular chromophore, BLA was fine-tuned by varying solvent polarity. The degree of BLA was analyzed by X-ray diffraction, 1H-NMR and electronic absorption spectroscopy. Non-resonant, solvent-dependent, electric field induced second harmonic generation (EFISH) Measurements were performed to probe the variation in the second-order nonlinearity as a function of ground-state polarization. The resulting trend, which is fully consistent with theoretical predictions, identified chromophores possessing optimized positive and negative hyperpolarizabilities. An optimized chromophore was incorporated in a polymer matrix and poled. The resulting electro-optic coefficient was found to be significantly enhanced relative to the longer chromophore Disperse Red 1.