We present a study of Distributed Feedback laser emission in various polymer materials. This permits efficient control of the stimulated emission in dye doped polymer materials. Confinement and waveguiding effects are evidenced. We also propose a dynamical study of the effect using 4 wave mixing in the saturable absorption regime with stimulated emission.

We report on a method developed for characterization the third order optical nonlinearity of singlemode polymer optical fiber. The Sagnac homodyning method yields values for both the real and imaginary components of (chi) ⁽³) from a single measurement. The method also allows for the separation of the effects due to nonlinear mechanisms having response times on the order of milliseconds or slower. The 10micrometers core of the characterized fiber was doped with 0.15 percent by weight of the squaraine HSQ. The real component of the nonlinearity was determined to be Re((chi) ⁽³) equals -9.8 +/- 2.5 X 10^-12 esu, and the imaginary component Im((chi) ⁽³) equals 5.5 +/- 0.3 X 10^-12 esu.

Single beam zscan experiments were carried out using a 130 fs tunable Ti:Sapphire-OPA laser system. The size and the sign of the third order susceptibility were measured at 400 nm, 590 nm, 648 nm, 800 nm, and 1000 nm. At 800 measurements were conducted for different pulse durations between 130 fs and 1 ps. Our results show that the measured values of the third order nonlinearity were relatively large, negative, and strongly dependent on pulse duration and wavelength. We found that, when wavelength and pulse duration are taken into account, the third order susceptibility of Gd₂ at C₈₀ is about one order of magnitude larger than that of empty-cage C₆₀ or C₇₀.

The narrowing of the super-broadened wings of both stimulated Rayleigh and Raman scattering (SRS) spectral profiles in carbon disulfide (CS₂) has been observed in a liquid-core hollow fiber system doped with 10 ppm of a dye. The observed red-shifted super-broadening effect of the SRS lines in transparent molecular liquids is caused by a nonlinear optical effect. It involves the light-induced reorientation of anisotropic molecules, a process in which the rotational work is done against the local viscosity. Pure and dye doped CS₂ SRS spectra were obtained for resonant and nonresonant pumping in order to verify the dependence on the spatial anisotropy of the absorbing molecules. The remarkable change in the spectral profile for the resonant case is explained in terms of the change in the guest-host interaction induced by optical excitation into the dye. This effect is attributed to the light-induced molecular pre-alignment of the anisotropic molecules of CS₂ caused by the reorienting mechanism of a majority of excited dye molecules along the optical pump field. Such phenomenon was reported recently in light-induced birefringence experiments by doping liquid crystals with an absorbing dye, leading to an enhancement factor by one to two orders in magnitude for the optical Kerr effect.

We report on the optical characterization of a series of multi-layered organic superlattices made by polyelectrolyte self-assembly. Using a high molecular weight, water-soluble, anionic form of poly-phenylene vinylene, self-assembled films can be formed which show high photoluminescence quantum efficiency (QE). A dramatic red shift of the luminescence and increase in QE is observed as additional PPV layers are added. We attribute the red shift and increasing QE to a changing conformation of the polymer chains as the superstructure is assembled, together with efficient Frster energy transfer in a preferred direction away from the substrate toward layers with longer effective conjugation length. Upon adding a C₆₀ top layer, the luminescence spectrum is strongly quenched. We attribute this to charge transfer of from the top-most polymer layer to the C₆₀ layer. We discuss the possibilities of exploiting this directional charge transfer in an ultrafast holographic device along with other optics for increasing the temporal diffraction efficiency of polymer-based mediums.

Anisotropy of transient absorption change and electroabsorption response in metallophthalocyanine (MPc) aggregates were investigated in terms of the influence of intermolecular interaction to the 2D character of the molecule. In an MPc aggregate intermolecular interaction with less symmetry might result in appearance of 1D character, depending on the nature of interaction and arrangement of molecules. In experiment, polarization- dependent electroabsorption response in various MPcs doped in PMMA presented a 1D character at the red-shifted absorption band due to coplanar intermolecular interaction and a 2D one at the blue-shifted band due to cofacial interaction. Polarization-dependent subpicosecond transient absorption change in various aggregate vanadylphthalocyanine, evaporated and doped-polymer films in phase-I and phase-II aggregation, presented a variety of anisotropy: in phase-I aggregate doped in polystyrene, a wavelength-dependent anisotropy similar to that of electroabsorption response was obtained; in phase-I aggregates doped in PMMA or evaporated, a 2D character was observed in almost whole wavelength region; in phase-II aggregates both 1D and 2D characters were in the red-shifted absorption band. These result are partly elucidated by the exciton coupling model in 2D molecules. It is also suggested that pump wavelength dependence of anisotropy and existence of two or more aggregate species might play important rolls.

The polymer crystals of the soluble polydiacetylene 4BCMU are thermochromic. Four distinct phases have been identified: the low temperature, highly ordered, crystalline Blue Phase I; the high temperature, semi-disordered mixed phase consisting of the crystalline Red Phase II and liquid- crystalline Yellow Phase II; the low temperature, highly ordered, crystalline Red Phase III; and the highly disordered, amorphous Yellow Melt Phase. The structure of the crystals and the conformation of the backbone and sidegroups are reported. The structure of the phases in the solutions and solution-caste films are also identified.

In order to improve third-order nonlinear optical properties of polydiacetylenes (PDAs), we have been investigating modification of PDA structures. From the point of view of PDA molecular design, three series of monomers for ladder- type PDAs were prepared. Oligoyne monomers having more than five conjugated acetylenes gave polymers which showed broad bands at longer wavelength than their excitonic absorption bands. This implies production of (pi) -conjugated ladder polymer having two PDA backbones linked by acetylenic groups in each repeating unit. From monomers with two butadiynes connected by an alkylene group, ladder-type PDAs were obtained when the carbon number of the alkylene group is more than four. However, monomers with two butadiynes connected by an arylene group gave only single-chain PDAs. From the point of view of PDA morphological engineering, PDA microcrystal water dispersions were applied to evaluate nonlinear optical susceptibilities by z-scan method together with PDA thin films. High-density microcrystal deposited film prepared by layer-by-layer deposition technique showed more than three orders of magnitude enhanced (chi) ⁽³) than the dispersion state. Polycrystalline thin films compose of ladder-type PDAs were also found to have large (chi) ⁽³). The quite large nonlinear refractive index of -41 cm²/GW was attained just near excitonic absorption maximum for one of the polymers.

We have developed a femtosecond continuum spectrometer to measure nonlinear absorption spectra from 300 nm in the UV to 1.7 micrometers in the IR. This method is applied for measuring NLA spectra of semiconductor, organic and polymeric materials. The pump-probe nature of the experiment also allows the temporal response to be determined, thus helping in the determining of the underlying physical mechanisms for the nonlinearity. We describe studies of two-photon absorption in a series of alkyl fluorenes and excited state absorption dynamics in a series of polymethines using this spectrometer.

This work aims at understanding how the liquid crystal device geometry affects its transient nonlinear response to 6-9 ns laser radiation, 10-Hz repetition rate. Results reported here are from Z-scan measurements at 0.532-micrometers laser wavelength of two pure liquid crystals with 'rod-like' molecules of similar chemical composition, but distinguished by conformal differences, i.e., 5CB and chiral CB15.

We demonstrate theoretically and experimentally that initially Gaussian optical beam sent through the (pi) -step phase mask and launched into a thin film of polymer poly(methyl methacrylate) doped with laser dye 4- (Dicyanomethylene)-2-methyl-6-(p-dimethylaminostryl(4H-pyran known as DCM evolves into a spatial structure similar to the dark spatial soliton. This takes place due to the third order nonlinearity associated with the mechanism of unconverted photobleaching of the dye-doped polymer. The result of the structuring of the beam is the formation of a permanent pattern of the refractive index of the film that acts as a channel waveguide trapping a weak Gaussian probe beam coaxial with the main beam. We also demonstrate theoretically the possibility of trapping the probe beam, which propagates in opposite direction at an angle to the main beam. The proposed theoretical model is nonlocal in time and is based on the Shrodinger-type nonlinear propagation equation for the main beam and the propagation equation for the probe beam complemented by the rate equation for the light-induced decrease of the refractive index. The results of this study can find application in optical interconnects and data processing.

The dynamical evolution of bright screening-photovoltaic (SP) spatial optical solitons in biased photovoltaic- photorefractive materials is investigated under steady-state condition. Our numerical study indicates that these SP solitons are stable against small perturbations whereas optical beams that significantly differ from soliton solutions tend to experience larger cycles of compression and expansion.

The femtosecond optical heterodyne detected otpical Kerr effect is described. The real and the imaginary parts of complex third-order optical nonlinearity can be effectively speared and their values and signs can be determined. Using this method, we have thoroughly investigated the substitution effect by adding side-groups on the -(-C equals N- )-conjugated system, a new class of nonlinear optical material, and find that the polybenzonitrile is an order of magnitude superior to poly-amino-nitrile. But when we further add substituents on benzoid rings, the enhancement is limited. We can say that for the series of polybenzonitrile, the benzoid ring can improve the (chi) ⁽³) value more effectively than other substitutions. We also find the value of second-order hyperpolarizability depends on the polymerization degree, and have discussed the saturation effect when the polymerization increases.

By using the femtosecond optically heterodyned optical Kerr effect at 647.0 nm we have measured the magnitudes and signs of the real components of third-order nonlinearity of organometallic compounds films of C₆₀M₂ fabricated through a series of reactions of C₆₀ anions with some inorganic compound in solution phase and physical jet deposition technique. We find there is an enhancement of the real components of third-order optical nonlinearities of C₆₀M₂ films compared to that of pristine C₆₀ film, which can be attributed to the charge transfer from metal atoms to C₆₀ molecules. The signs of the real components of third-order optical nonlinearity of C₆₀ and C_{60$M(subscript 2} films are negative. We also find the disposition temperature will affect third-order optical nonlinearities of C₆₀M₂ films.

We have studied the two-photon absorption (TPA) and fluorescence properties of a series of phenylpolyenes with N-carbazolyl as donor end-groups in symmetric positions. The symmetric substitution of carbazole end-groups enhances the photostability of the molecules and maintains high TP coefficients. High fluorescence quantum efficiencies have been measured. The results suggest that TP chromophores with carbazole donors are promising materials for applications in two-photon imagin and sensitization. The study covers a broad excitation spectrum from 580nm to 820nm using a picosecond optical parametric source. We take advantage of the correlation between idler and signal waves emerging from the parametric generator and calibrate our results against Rhodamine B for which reliable data is available in the long wave range.

Anisotropy of third-order nonlinear optical properties in di-n-butyl fluorescein derivatives was investigated by electroabsorption spectroscopy. In a series of fluoresceins, the derivatives with Cl substitution at phenyl ring presented a new intense absorption band at the wavelength range from 550 to 620 nm, which is at longer wavelength side of the main absorption band in other derivatives. This new absorption band was attributed to intramolecular charge transfer transition due to Cl substitution at the phenyl ring, according to the spectral profile of electroabsorption which was proportional to the second derivative of linear absorption spectrum. Polarization dependence of normalized absorption coefficient was about 2:1 at the main absorption band in all derivatives. However, in the charge transfer transition band, the polarization dependence was about 1:1,2, suggesting that the charge transfer direction is nearly perpendicular to the otpical transition. This result is consistent with structural aspect that the charge transfer direction is located along to the bond between the Cl-substituted phenyl ring and condensed ring, while the optical transition is along to the longitudinal axis of the condensed ring.

Bis-(diphenylamino)diphenylpolyenes have been shown to form exceptionally stable, highly absorbing bipolaronic dications in solution and thin film. Replacement of one diphenylamino substituent with a N-(hydroxyethyl), N-ethylaminophenyl moiety yields a polyene series that also form stable bipolarons, and are intensely fluorescent. These new chromophores are also easily attached to either a PMMA backbone or to 3,5-dihydroxybenzyl alcohol to yield functionalized dendrons capable of attachment to various core molecules to yield functionalized dendrimers. Diphenylamino-substituted PPV oligomers can also be obtained with similar functionality. These new materials all possess large two-photon cross-sections and display optical limiting for nanosecond pulses with peak activity extending into the visible portion of the spectrum. In this presentation we will discuss the synthesis of these new materials and preliminary characterization as two-photon absorbers, photoluminescent materials suitable for organic light- emitting diodes, and as dendrimers capable of 3D charge delocalization and exceptionally large third order hyperpolarizabilities.

Our preliminary results on the synthesis and characterization of a new family of coordination polymers incorporating 8-hydroxyquinoline is described. The new polymers have the following structural features: a metal center, a chromophore, and a flexible spacer group with variable length. These structural features allow us to have an appreciable degree of control over various physical properties of these materials. We report on three different types of polymers: polyethers, polyesters, and polyamides. The chromophores in these polymers were incorporated in the backbone and in one case as a side chain of polyesters.

We have synthesized two chromophore monomers, starting from chloromethyl styrene and methyl methacrylate, and the corresponding homopolymer and copolymer. The obtained structures have been characterized by UV-Vis, IR and H-RNM. The molar fraction of the chromophore monomers in copolymers have been determined by H-RNM and elementary analysis. We have measured the NLO third order coefficients by the degenerated four wave mixing method and high values have been obtained.

The design of new organic chromophores with enhanced nonlinear optical (NLO) response over the past several years has focused on several structure-property relationship paradigms. The extension of the conjugation sequence leads to increases in both the second order and third order hyperpolarizabilities. Electron-donating or withdrawing substituents also affect the electron distribution along the conjugation sequence, and such substitution has been utilized in concert with the conjugation length dependence to tailor the molecular absorptivities and polarizabilities. In addition, previous studies of the NLO properties of organic chromophores have shown enhancement of the NLO response when second row elements replace first row elements in the structure. Various substituted amino groups have been used extensively in the design of both second and third order chromophores as strong donor groups. However, to date there have been no systematic studies of the effect of replacing P for N in various chromophore functionalities. In this presentation we will discuss the syntheses of several new chromophores with diphenylphosphino substituents, and compare their structure-property relationships to the equivalent, and more familiar, diphenylamino-substituted chromophores. In particular we will focus on their respective absorption properties in the visible portion of the spectrum, and the possible consequences for NLO applications.

Machine dyes are frequently used as nonlinear optical (NLO) chromophores. In the case of our dyes, both, the substitution of the methine proton by a cyano group and the substitution of the methine carbon by nitrogen, lead to a strong bathochromic shift. In this work the influence of these modifications to the first hyperpolarizability is systematically investigated.

A series of novel metal-organic in-plane complexes trans- (formula available in paper) have been investigated using the hyper-Rayleigh scattering technique. Like other in-plane complexes reported recently they exhibit very large and tunable static first hyperpolarizabilities which are associated with intense visible metal-to-ligand charge-transfer excitations. Moreover, a good correlation was found between the hyperpolarizabilities and the electrochemical properties of the complexes. Furthermore, the effect of the oxidation state of the metal upon the molecular optical nonlinearity has been investigated. Chemical oxidation of the metal is proven to be an excellent tool to reversibly switch the molecular first hyperpolarizabilities of the trans- substituted ruthenium complexes.

New colorless salts of 4-carbamoylpyridinium benzenesulfonate derivatives having hydroxy, methoxy or bromo substituent with second-order optical nonlinearity were synthesized. Their x-ray structural analyses have been performed. Intermolecular hydrogen bond formation between sulfonate group and carbamoyl group as well as between carbamoyl groups of adjacent cations were observed in the crystals. Using a simple oriented-gas description, non- diagonal second-harmonic coefficients of the crystal were estimated to be not too far form that of colored N-(4- nitrophenyl)-(L)-prolinol. The easy single crystal growth and good transparency in visible region suggest that they may be applicable as crystals for frequency conversion of conventional laser diodes.

A computer program has been developed to calculate crystal susceptibility tensor components. In addition to previous considerations where molecular polarization tensors have been treated as 1D or 2D, the present program allows the use of the 3D case that appears necessary for non-planar molecules. Calculation of crystal susceptibility is based on the approximation of relatively weak intermolecular forces in relation to intramolecular ones. Local field corrections have been estimated using simple Lorentz form. To provide molecular second-order polarizability, a semiempirical quantum chemical calculation has been carried out using the finite field method incorporated in the MOPAC program.

The nonlinear optical behavior of self-assembled monolayer films of a new NLO-active molecule, PBSP, is characterized by second harmonic generation (SHG). PBSP contains a heterocyclic sulfonate head group and a highly polarizable chromophore. The films are synthesized by a nucleophilic substitution reaction on both sides of a quartz substrate that has been treated with a coupling layer. The addition of the chromophoric layer is monitored by AFM, FTIR and UV- visible spectroscopy, and SHG. The FTIR spectrum of the first layer shows weak methylene resonances, while the spectrum with the addition of the second layer shows much stronger methylene resonances and an amine resonance. The characterization of the film by SHG was done by rotating the film and generating Maker fringes. The polarization dependence of the SHG signal was also determined. The SHG signal after the nucleophilic reaction was an order of magnitude greater than before the reaction. The magnitude of the dominant element of the nonlinear susceptibility and the average molecular orientation angle of the chromophore were determined by modeling the Maker fringes and the polarization dependence of the SHG signal.

We have designed and synthesized donor/acceptor substituted hexatriences 10,11, in which the configuration is locked by a hexahydroanthracene frame. Donors and acceptors of varying strength were introduced. In order to assess the potential of our merocyanines 10,11 for NLO and photorefractive (PR) applications, we have measured their linear and nonlinear optical properties and determined the NLO and PR figures-of- merit (FOMs), respectively. The merocyanine 10d exhibits a very large Kerr FOM. The thermal stability of the new merocyanines 10,11 is sufficiently high for photonic applications. In order to investigate and to correlate the bond length alternation of our oligonenes 10,11 with linear and nonlinear optical properties we have carried out x-ray structure determinations.

Catenanes are a new class of potentially interesting materials for application in photonics. Good optical quality thin films of a benzylic amide catenanes were obtained by vacuum evaporation. They exhibit a large transparency range with cut off at around 300 nm and a large refractive index. The propagation losses depend on the wavelength and ar of 2.8 dB/cm, 4.5 dB/cm and 30 dB/cm at 1314 nm, 1550 and 633 nm, respectively. At 633 nm the propagation losses are clearly due to the Raleigh scattering. The cubic susceptibility measured by the optical third harmonic generation is of (3.4 +/- 0.4) X 10^-13 esu. The as deposited thin films are anisotropic and exhibit second harmonic generation as well as the linear electro-optic effect. However the linear electro-optic coefficient is about two orders of magnitude larger than that expected from SHG measurements, indicating clearly the ring mobility under the applied external electric field.

Two different types of dipolar cationic sesquifulvalene complexes were prepared and investigated by electrochemistry, UV-vis spectroscopy and hyper-Rayleigh scattering: i) monocationic, mononuclear species with different spacers Z, and ii) dinuclear derivatives with different electron acceptors, and the five- and seven- membered rings in close contact.

The second order nonlinearity of conjugated organic molecules involving, 1,3 indandione derivatives as an acceptor moiety has been studied. Varying the donor from dialkylamino to the chemically similar substituent, N- carbazolyl resulted in a drastic reduction of electric field induced second harmonic (beta) values. For some molecules, even a small negative value of (beta) was received. Quantum chemical calculations indicate that the decrease occurs as a result of two overlapping transitions, which contribute to (beta) with opposite signs. The charge transfer band gives a positive (beta) _{zzz along the molecular long axis, while a transition essentially within the carbazole moiety provides a negative (beta zzz contribution to (beta} ^EFISH. Thus, these molecules must be described with a 2D model as opposed to the 'classical' model of 1D nonlinear optical chromophores. The prediction of the 2D model was verified experimentally by using a combination of two methods, EFISH and Hyper-Rayleigh Scattering, which probe different combination of the (beta) tensor elements.

Resonant molecular optical second harmonic generation (SHG) was obtained from(2, 3, 7, 8, 12, 13, 17, 18-Octaethyl- porphinato)M, with M equals none, vanadyl and Ni(II), adsorbed onto fused silica substrates. The polarization dependence of the SHG signals at 1064 nm allowed the determination of average molecular orientations. For the vanadium porphyrin the average angle between the long axis molecules and the surface normal was 38 degrees, while, for the Nickel porphyrin, and the non-metal porphyrin the angle was close to 0 degrees. These results can be understood in terms of the different symmetries of the molecules.

For a large class of practical applications, based on second order nonlinear optical effects, one needs not only noncentrosymmetric molecules, like charge transfer molecules, but also their assemblage to macroscopically noncentrosymmetric materials.

Electrooptic films based on a new class of porphyrin chromophores with exceptionally large molecular first hyperpolarizabilities are begin developed. These chromophores feature donor and acceptor groups linked to the porphyrin macrocycle at the 5- and 15-meso positions through intervening ethynyl moieties. We report herein preliminary result that describe the ambient temperature assembly of ordered, electrooptic films using the Langmuir-Blodgett-Kuhn method. The facile formation of such films was mae possible by the preparation of amphiphilic chromophores containing hydrophobic aliphatic substituents to enhance the polar alignment at the air-water interface. Second harmonic generation and UV-Vis absorption were used to characterize the films as a function of the number of layers deposited. Polar films containing up to 10 layers were made by simple Y-type homolayer deposition, and up to six layers by the Y- type heterolayer method in which the porphyrin layers were interleaved with poly(t-butyl methacrylate). The polar order in these films relaxed exponentially. Ionic structures are recommended for improved stability.

The second-order nonlinear properties of step-index polymer electrooptic (EO) fiber are discussed. The fiber is fabricated in the Nonlinear Optics Laboratory at WSU. Use of a Mach-Zehnder interferometer to determine the linear electrooptic coefficient of the EO fiber and quadratic electrooptic coefficient for a thin film is discussed. The data thus obtained is shown to be reproducible and of correct magnitude.

Highly efficient refractive index gratings, 35 percent or more, were fabricated by photobleaching into an azo polymer film with a large second-order optical nonlinearity. From IR spectroscopy, it was confirmed that 532 nm laser light cause photobleaching of azo polymer film effectively. As the modulation depth of relief structure observed by AFM was less than 30 nm, the effect of relief structure observed by AFM was less than 30 nm, the effect of relief structure on the diffraction efficiency is negligible. From these results, we confirmed that the grating obtained in this experiment was mainly caused by photobleaching. We observed that coupling efficiency of the grating is dependent on polarization direction of guiding beam. This is considered to related to the anisotropic refractive index change due to the photobleaching in vertical plane of film.

We report here on the synthesis of new polymers carrying chromophores active for second- and third-order nonlinear optical (NLO) applications. Some of these systems show exceptionally large NLO molecular properties such as high first hyperpolarizabilities and high two-photon-pumped frequency-upconversion lasing efficiencies. Different types of polymeric and copolymeric backbones have been investigated in order to tune the properties of the bulk material and optimize its efficiency. Factors such as the linking reaction approach, chromophore number density, cross-linking ratio, and thermal properties can be controlled and tuned depending on the application. In particular, we have found that NLO molecular components carrying a primary amino group attached to the chromophore by means of a short aliphatic chain can act as comonomers in poly(amino-amine) synthesis, a family of synthetic polymers in which amido and tertiary amino groups are regularly arranged along the main backbone. Linear and soluble, or, alternatively highly crosslinked poly(amido-amine) networks can be easily obtained with high loading of the chromophore. In addition, hydroxylated chromophores can be covalently linked to properly functionalized acrylic polymers, such as poly(2-methacryloxyethyl)imidazolylformate.

Low halfwave voltage electrooptic modulators are desired in many applications. In this paper, two halfwave voltage reduction approaches are presented based on novel modulator architectures and the flexible processing properties of electrooptic polymers. Both approaches can significantly improve the modulation efficiency without compromising device performance. The fist is an optical push-pull approach in which the two arms of a Mach-Zehnder modulator are poled in opposite directions and a single microstrip line traveling wave electrode is used to maintain a wideband frequency response. A 50 percent reduction in halfwave voltage was obtained using the optical push-pull architecture. The modulation efficiency for optical push- pull is 3 dB higher than electrical push-pull because it uses only one modulation input source while electrical push- pull requires a 3 dB microwave splitter and phase inverter to drive two electrodes. The second approach is to fabricate an electrooptic polymer modulator using active polymers for both waveguiding and cladding layers. When a modulation electric field is applied, the index modulation in both guiding and cladding layers will result in a larger effective index modulation than that in structures with only an active guiding layer. Theoretical analysis, poling and driving electrode layout, fabrication techniques, and experimental results are discussed.

We present a method for analyzing the homogeneity of the (chi) ⁽²) distribution in poled nonlinear optical polymer films. The second order nonlinear coefficient in these polymers is commonly induced by electric field poling methods which can lead to a (chi) ⁽²) distribution with poor spatial homogeneity. In this paper, we analyze the (chi) ⁽²) distribution using scanning Kelvin microscopy. This allows us to detect the height and the direction of the induced polarization through the probing of the counter charges that are present on the polymer surface. We compare the response to that obtained from the scanning second harmonic microscopy (SSHM) method, in which the direction of the orientation, and thus the phase of (chi) ⁽²), can not be seen. We also propose a method to measure the (chi) $_(2)) distribution in 3D by analyzing the SSHM images obtained at various wavelengths.

A series of novel bifunctional cyclosiloxanes with pendant photoconducting and nonlinear-optical moieties was synthesized in a two step procedure. The variation of the spacer length between the siloxane ring and the functional carbazole and azo moieties leads to glass transition temperatures between 33 degrees C and 61 degrees C. These well defined low-molar mass compounds are characterized with regard to their chemical, thermal and electrooptical properties. Compared to commonly used guest-host systems crystallization of the chromophore dopants is diminished due to the covalent bonding of the azo-dye to the cyclosiloxane backbone.

The resistless process of the photochemical formation of nonlinear optical pattern in the polymer layer was elaborated. The illumination of the polymer donor-acceptor layers consisting of poly(hydroxyaminoester) as a donor and tetrabromomethane as an acceptor provides second harmonic generation (SHG) due to the photochemical formation of the Michler's hydrol blue like fragment (MHB⁺). The square root of the SH intensity, I^0.5, linearly increases with the increase of exposure dose in region H <EQ 120 mJ cm^-2. SHG is absent on unexposed areas of the same layer. SHG arises due to transformation of the geometry of MHB⁺ cation from centrosymmetric to noncentrosymmetric because of bond-length alternation under influence of Br counteranion.

The nonlinear optical properties are reported for a novel organic dendrimer using femtosecond pulses. The organic dendrimer showed strong nonlinear refraction when measured at 790 nm, a wavelength far from the linear resonance. The nonlinear refractive index was measured by the z-scan technique and the magnitude was measured to be 1.1*10^-4 cm²/GW. The presence of two photon absorption was observed and a related nonlinear absorption coefficient was found to be 1.2*10^-2 cm/GW. A strong two-photon luminescence was detected resulting from this nonlinear absorption, and the power dependence and spectral characteristics were measured. The presence of a higher order, (chi) ⁽⁵), nonlinear optical effect was also detected. The ultra-fast dynamics of the organic dendrimer using fluorescence upconversion spectroscopy are reported. At higher emission energies we observe femto-second decay, and at lower energies a rise time of the luminescence intensity was observed.