Employing guidance from quantum and statistical mechanics, the electro-optic activity of organic materials has been increased to values greater than 100 pm/V at telecommunication wavelengths (e.g., 130 pm/V at 1.3 microns). Electro-optic materials now afford significant advantages in terms of bandwidth and electro-optic activity over competitive inorganic materials such as lithium niobate. Organic materials have also been found to be quite processable permitting the fabrication by reactive ion etching and photolithographic techniques of 3-D active waveguide structures and integration with both VLSI semiconductor electronics and silica fiber optics. Both stripline and microresonator structures have been fabricated, as have low-optical-loss coupling structures. A number of prototype devices demonstrating superior performance have been demonstrated; however, the long-term, in-field performance of such devices still remains to be evaluated. This article focuses on statistical mechanical theoretical methods that have aided the design of improved materials.

Quantum wave packet engineering is demonstrated using a phase-programmable femtosecond optical source. This paper describes development of a programmable phase modulator and coherent control of quantum wave packets. Wave packet motion in a cyanine dye molecule is observed to be dependent on the chirp direction and rate of excitation pulses. Strong reduction in excited state population is efficient for negatively chirped pulses in the cyanine dye molecule, which is explained in terms of a pump-dump process. We discuss a possibility of mutual conversion between the optical and electronic phase information by means of nonlinear light-matter interaction.

Recent development of dendron-containing NLO chromophores and polymers is summarized. By modifying the chromophore shape or applying the site isolation principle to these materials, we have systematically build up our understanding of how to molecular engineer the NLO materials. In this process, we have introduced the dentritic structures to these materials, varied from 3-D shaped dendritic chromophore, to fully-functionalized dendrimers with the center cores of NLO chromophores and crosslinkable periphery, and to side-chain dendronized NLO polymers. Compared to the conventional designed organic NLO materials, these nanoscale tailored NLO chromophores and macromolecules provide great opportunities for the simultaneous optimization of macroscopic electro-optic activity, thermal stability, and optical loss.

The octupolar framework provides a promising route towards molecular compounds combining enhanced NLO responses and improved nonlinearity-transparency trade-off. In this perspective, we have designed original three-branched boomerang-shaped nanoscale molecules. Their molecular design is based on the grafting of three conjugated blades bearing either an electron-withdrawing or an electron-releasing end group on a triphenylbenzene core which can act as a (weak) donor or acceptor counterpart. We selected oligomeric phenylene-vinylene conjugated rods to allow for efficient charge transfer between the center and the periphery of the molecule while preserving transparency. Based on this strategy, we have prepared homologous nanoscale molecules with size varying between 2 and 5 nm. These molecules exhibit a definite solvatochromic behavior, in consistence with a multidimensional intramolecular charge transfer (MDICT) taking place between the core and the peripheral groups. Large first-order hyperpolarizabilities could be achieved by taking advantage and boosting of the MDICT phenomenon while maintaining wide transparency in the visible region (up to ||β|| = 800 10^-30 e.s.u., with λ_max = 377 nm). The superlinear dependence of β on size and their concave shape make elongated analogues attractive candidates for future developments.

Dendrimers are capable to encapsulate small molecules inside them. Because three-dimensional structures of dendrimers are highly controllable, energy transfers among dye molecules encapsulated inside them can be controlled precisely. Electronic energy transfers from optical excited molecules are categorized into two classes, Forster and Dexter types. Inter-molecular interactions between encapsulated dyes can be expressed as the Forster (singlet-singlet) energy transfer, because the size of dendrimers extends to a few nanometers. We have evaluated time resolved optical responses in rhodamine-cored dendrimer films. Fast decay in fluorescent lifetime is observed and it depends on the dendrimer size. A low generation dendrimer shows lifetime as short as 10 psec without severe quenching of fluorescence. A quadratic dependence of the emission intensity on density of molecules indicates that the origin of the short lifetime is not only energy transfer, but also super-radiance. Since the Dexter (triplet-triplet) energy transfer occurs in short range of 1.0 nm, we attached both donor and acceptor molecules to a dendrimer for investigation. We demonstrated photocrosslinking via triplet-triplet energy transfer from donor molecules encapsulated to acceptors attached at the surface. This procedure of triplet-triplet energy transfer in dendritic molecules opens up way to design novel optical and electrical molecular devices.

Optical phase conjugation (PC) by non-resonant degenerate four-wave mixing (DFWM) in thick media of poly(methyl methacrylate) (PMMA) with doped disperse red 1 (DR1) is reported. With vertically polarized counterpropagating pump waves, PC reflectivities of 43% and 37% were achieved respectively for a horizontally and vertically polarized probe wave, which is more than 50 times higher than the value reported on resonance. Reflectivities over 30% were achieved over a wide range of intensity for both polarization configurations. Photoinduced modulation of ordering of the DR1 chromophore is the main mechanism of the PC wave generation. Other mechanisms involved in the configuration of all vertical polarization waves are also examined. Influence of the squeezing process in making volume samples on the PC wave efficiency is significant.

Polymers doped with nonlinear optical (NLO) chromophores are attractive candidates for manufacturing optical integrated devices, especially for applications based on second order non-linearities. Such optical devices require to select accurately the areas where the NLO push-pull molecules embedded in the matrix are oriented. This is usually achieved using patterned electrodes deposited onto the samples or microlithography techniques. We suggest a novel approach to control the spatial distribution of the oriented chromophores, based on the use of photopolymerizable mixtures. The formulation developed, which consists of a triacrylate monomer and a photoinitiator, is polymerized upon a visible light irradiation. It is doped with chromophores specially synthesized for this purpose, transparent at the actinic wavelength and highly soluble in the acrylate monomer. The doped photopolymerizable films are poled with a static electric field before irradiation and the orientation of the chromophores is then frozen in the desired areas by irradiating the samples with an appropriate pattern of light. We observed the ability of the polymerized medium to slow down the chromophore relaxation compared to the unexposed solutions. The influence of the formulation composition and irradiation parameters on the temporal stability of the chromophore orientation was studied through second harmonic generation measurements. Infrared spectroscopy measurements enabled to draw a correlation with the monomer conversion degree of the polymer host.

Optically pumped lasing action and recoverable photodegradation in the common organic dye 1-amino-2-methylanthraquinone (Disperse Orange 11) is presented. The dye was incorporated into polymethyl methacrylate (PMMA) rods and amplified spontaneous emission (ASE) was studied under second harmonic Nd:YAG laser excitation in a transverse pumping configuration. Gain and conversion efficiency is found to be comparable to other laser dyes with the stimulated emission centered at the attractive wavelength of 650nm. Photodegradation of the dye-doped-polymer is found to be superior and uniquely fully reversible.

Methods that successfully predict the refractive index at near-infrared wavelengths of negatively birefringent polymer films for optical waveguide applications are presented. The starting point for these methods is a correlation based on connectivity indexes originally developed by Bicerano for the refractive index of isotropic polymers at visible wavelengths. This correlation is applied to a set of polyimides at near infrared wavelengths with modifications in order to improve its predictive power. The polyimides were synthesized by condensation of monomers to form the precursor poly(amic acid)s followed by imidization in solution. Solutions of the polyimides were then spin coated onto glass substrates and baked to produce films of 2-3 microns in thickness with a variable negative birefringence. The refractive index profiles of these films near 1320 nm were then measured in both the TE- and TM- modes using a prism-coupling technique. The average refractive index of these films was then compared to the prediction generated by the model. The agreement between the predicted and observed values has been sufficient to enable the rapid development of materials for optical waveguides without the need for many rounds of trial-and-error investigation. These techniques facilitate the development of specialized polymers for optical waveguide applications.

In photorefractive guest-host polymers, fast orientational dynamics of push-pull chromophores are needed to obtain the so-called orientational enhancement as well as high performances. For this purpose, a better understanding of the relationships between viscoelastic properties of polymers and orientational processes of chromophores is now essential for the optimization and the development of new efficient photorefractive polymers. In the present investigation, the orientational dynamics of the chromophores are probed in details by dielectric spectroscopy, second-harmonic generation and ellipsometric techniques, in various doped polymers. The materials are based on a polyvinylcarbazole plasticized with N-ethyl carbazole, a polysiloxane functionnalized with a carbazole pendant, as well as polystyrenes with different average macromolecular weights. The temperature-dependencies of their dielectric and electro-optic responses provide information on the rotational mobility of the chromophores at a microscopic scale. These data are directly compared to the temperature-dependence of the viscoelastic properties, characterized at a macroscopic level by shear compliance measurements. The analysis reveals the strong coupling between the orientational processes of the chromophores and the polymer chain dynamics. The effects of other physical parameters (applied voltage magnitude, amount of plasticizer, average molecular weight of the polymer host) on the orientational dynamics of chromophores are also investigated in order to describe the mechanical interactions between the chromophores and the polymer host. Finally, a new way of optimization for photorefractive polymeric material properties is suggested.

Silicones are among the most suitable materials for optical telecommunication devices due to their tolerance to high optical flux and their thermo-mechanical and environmental stability; they also have excellent processability. This work focuses on utilizing silicon-based branched resins and linear polymers for optical waveguides and switches where both refractive index and thermo-optic coefficient need to be controlled to the requirements of specific applications. Materials were synthesized with high optical transmission bands between 1.3 and 1.6 μm by varying the amount of aliphatic and aromatic C-H in the material. At the same time, the ratio of methyl to phenyl groups also controls the refractive index in the range of n_D = 1.4 ... 1.6 precisely enough that both core and cladding components (Δn < 0.5%) can be obtained. Films of 5 to 20 μm thickness prepared on silicon substrates by spin-coating from solution were evaluated by measuring refractive index, thermo-optic coefficient, optical loss, and film uniformity both before and after exposure to high temperature and humidity. These films can be patterned through a number of techniques to form the required features. The resinous materials show very low birefringence and excellent resistance to heat and moisture.

Linear and nonlinear optical properties of a new soluble polymer bearing distyrylbenzene chromophore, the alkoxy-sulphono-substituted p-phenylenevinylene oligomer (MTPV-ORSO) attached as a side-chain to the methyl methacrylate backbone are reported. This chromophore was developed for introduction into single-mode nonlinear optical polymer fibres. The molecular second-order and third-order nonlinearities were estimated with quantum chemical calculations (MOPAC). The side-chain polymer shows an optical absorption maximum at 326 nm. The polymer was incorporated into the core of the fibre preform with a procedure which led to a step index profile, as measured with a preform profiler, suitable for a single-mode optical fibre. Second harmonic of the fundamental 1200 nm wave was measured in the corona poled polymer films giving the second-order susceptibility d₃₃ = 0.8 pm/V for the polymer containing about 1.3 wt% of the side-chain chromophore and 0.1 pm/V in a guest-host system containing 0.24 wt% of the chromophore in the fibre preform. The coherence length of the side-chain polymer, equal to 28 μm at 1200 nm, was evaluated from the dispersion of the linear refractive indices. Degenerate four-wave mixing (DFWM) with amplified femtosecond pulses was also applied to measure the nonlinear refractive index of the co-polymer at 800 nm.

Two examples of efficient and reversible switching of the first hyperpolarizability of charge-transfer metalorganic species are presented. The charge transfer is between a metalorganic donor unit and an organic acceptor. In one case, the donor is a ruthenium(I) pentammine complex, the acceptor is an N-methyl-4,4'-bipyridinium ligand. Oxidizing the ruthenium(II) to ruthenium(III) changes the donor to an acceptor and destroys the charge transfer, as evidence by the disappearance of the charge transfer band in linear absorption spectroscopy. In hyper-Rayleigh scattering, a reduction in first hyperpolarizability of at least an order of magnitude is observed. In a second case, the donor is an octamethylferrocene unit, while the donor is a nitro group on a thiophene. Again, oxidizing the octamethylferrocene to octamethylferrocenium reduces the hyperpolarizability with more than an order of magnitude. Both redox processes are fully reversible.

Langmuir-Blodgett films have been prepared from amphiphilc molecules containing an indandione-based nonlinear chromophore. Study of the pressure-area (π-A) isotherm enabled us to find optimal conditions for monolayer transfer to a glass substrate. The multilayer films thus formed exhibited strong optical second harmonic generation with a bulk nonlinear co-efficient equal to the ideal value predicted by the product of the chromophore density and its known molecular hyperpolarizability.

We report on a procedure to fabricate a specific micro-structured fiber with metal wires array running down its length. The goal is to develop an unique photonic bandgap lattices with enhanced optical nonlinearity. Mechanism of enhanced nonlinearity is briefly discussed. FDTD simulation on single-wire fiber is presented.

Azo-dye-doped polymers have a large intensity dependent refractive index with at least two mechanisms that are characterized by their response times and by the sign of amplitudes. τ₁ is in a range of 700ms to 900ms and τ₂ in a range of 50s to 60s. To charcterize the dynamics of the real and imaginary part of this response, we use a T-scan technique(using open and closed apertures), where the intesity dependent focusing/defocusing processes of the material is studied as a function of time.

Temperature effect on photoinduced third harmonic generation (THG) variation of an azo copolymer and an azo guest-host polymer is studied at two different temperatures. At higher temperature, both angular hole burning (AHB) and molecule angular redistribution (AR) motions are smaller due to the decrease of cis-trans thermal relaxation time and cis population. Smaller photoinduced THG change is observed in both samples at higher temperature. THG recovery experiment results show copolymer thin films pumped at high temperature have the best photoinduced THG variation stability after turning off the pump beam.

Monte Carlo simulations suggest that the functionalization of bulky side groups on highly efficient nonlinear optical chromophores will improve the poling efficiency of the electro-optic polymers by reducing the intermolecular electrostatic interactions from these large dipole moments (μ) chromophores. However, very little information has been provided from theoretical simulation to describe the optimal functionality of the bulky side group needed on individual chromophore in order to be compatible with its environment, e.g. neighboring chromophores and polymer matrix. To further understand the influence of side-chain modification of chromophore on both chromophore-chromophore and chromophore-polymer matrix interactions, we have synthesized a series of highly polarizable nonlinear optical chromophores with various side-chain modifications in terms of shape, rigidity and functionality. Linear E-O coefficients (r₃₃) of these functionalized chromophores in amorphous poly(carbonate) were evaluated using the contact poling technique. Several important chromophore and polymer parameters, such as, steric hindrance and free volume were used to explain the overall results from chromophore-chromophore and chromophore-polymer matrix interactions on E-O property.

The possibility to integrate an optical emitter at any point in a silicon integrated circuit would represent a major breakthrough in the field of optical interconnects. The outstanding properties of luminescent organic semiconductors, such as their ability to be deposited on various substrates and their efficiency, make them good candidates for this kind of applications, but organic light-emitting diodes (OLEDs) are characterized by broad spectra and angular emission patterns which prevent their integration in an optical interconnection system. So, we study resonant-cavity organic light-emitting diodes (RC-OLEDs) such as Al/ITO/CuPc/TPD/Alq3/Al which are made on silicon substrates. Aluminum is chosen to make the mirrors because of its compatibility with CMOS technology. The devices are characterized by electroluminescence, and their current-voltage characteristics are measured. We study the influence of the electrodes on the electrical characteristics of the devices. We describe these planar multilayer microcavities using a transfer-matrix multiplication method. The experimental results that we obtain with two samples allow us to calculate the dependence of the refractive index of the ITO layer on the wavelength. We compare our experimental and theoretical results and find a good agreement between them.

In this paper we describe methods of fabricating and characterizing organic electro-optic modulators based on intrinsically polar self-assembled superlattices. These structures are intrinsically acentric, and exhibit large second harmonic generation and electro-optic responses without the requirement of poling by an external electric field. A novel wet chemical protection-deprotection approach for the growth of self-assembled superlattices have been developed, and the refractive indices of self-assembled organic electro-optic superlattices may be tuned during the self-assembly process. Prototype electro-optic modulators based on chromophoric self-assembled superlattices have been designed and fabricated. The effective electro-optic coefficient of the self-assembled superlattice film in a phase modulator is estimated as about 20 pm/V at a wavelength of 1064 nm.

A multichromophoric nanoassembly was designed by gathering seven push-pull chromophores on a β-cyclodextrin assembling unit via covalent linkers. Such supermolecule provides a valuable model for the investigation of confinement effects on the linear and nonlinear optical properties of push-pull chromophores in the condensed phase. Push-pull chromophores display a significant ground-state dipole, thus promoting dipolar interactions that are expected to influence both the conformation and the optical properties of the multichromophoric assembly. In this perspective, the photophysical and nonlinear optical properties of the mutichromophoric bundle were investigated and compared to those of the monomeric chromophore. The absorption, circular dichroism and fluorescence investigations provide evidence that the push-pull chromophores do not behave as isolated independent chromophores within the multichromophoric assembly. The nanoscale supermolecule is hypsochromically and significantly hypochromically shifted with respect to its monomeric analogue. In addition, the close proximity promotes excitonic coupling, as well as excimer formation phenomena. The nanoscopic assembly also shows a very large dipolar moment (μ = 38 D), and a significant molecular first-order hyperpolarisability, which reveal a spontaneous sheaf-type self-arrangement of the dipolar chromophores within the supermolecule. Such chiral hyperpolar nanoassemblies are promising candidates as model systems for nanophotonics.

Photonic crystals (PC) are a class of artificial structures with a periodic dielectric function. PCs can be a laboratory for testing fundamental processes involving interactions of radiation with matter in novel conditions. We have studied the optical properties of opal PCs that are infiltrated with highly polarizable media such as j-aggregates of cyanine dyes. Opals are self-assembled structures of silica spheres. We report our studies on clarifying the relationship between a polaritonic gap and a photonic stop band (Bragg gap) when they resonantly coexist in the same structure. Infiltration of opal with polarizable molecules combines the polaritonic and Bragg diffractive effects. Both effects exist independently when the Bragg (at ω = ω_B) and polaritonic (ω = ω_T) resonances are well separated in frequency. A completely different situation occurs when ω_T ≈ω_B. Such a condition was achieved in opals that were infiltrated with J-aggregates of cyanine dyes that have large Rabi frequency. Our measurements show some dramatic changes in the shape of the reflectivity plateaus, which are due to the interplay between the photonic band gap and the polaritonic gap. The experimental results on reflectivity and its dependence on the light propagation angle and concentration of the cyanie dyes are in agreement with the theoretical calculations.

Optical limiting properties in CH₂Cl₂ solution of a series of axially substituted InTPP (indium tetraphenyl-porphyrin) and axially substituted InTTP (indium tetra-p-tolyl-porphyrin) are investigated using a 532nm laser with a pulse duration of 5 ns. The axial substitutions include -Cl, -SCN, -SPh and -SPh(p-Me). The optical limiting measurements reveal that the optical limiting properties of the indium porphyrins are greatly influenced by the axially attached functional groups. A limiting threshold of 0.18 J/cm² is achieved for TTPInSCN, which is the best optical limiting material in this report. Z-scan experiments are also conducted and confirm that the good optical limiting performance of these indium porphyrins is due to the large value of σ_ex/σ_g.

A series of functional and photo-crosslinkable maleate or fumarate type polyesters containing azo-type NLO chromophores were studied. The result demonstrated this is a versatile and convenient method of fabricating crosslinked supramolecular ultra-structure polymer thin films for potential nonlinear optical (NLO) and other photonic applications. The unsaturated PDRMA/PDRFC polyester thin films are capable of crosslinking in air via photo polymerization to form a hardened lattice. A ratio of 1:1 of crosslinker double bonds to polyester double bonds was preferred for optimal crosslinking. Thermal stability of Second Harmonic Generation (SHG) signals for a photo crosslinked polymer thin film reached to about 150°C. Films from photo crosslinking of fumarate or maleate vs. vinyl crosslinkers have the advantages of avoiding NH/OH groups and their vibrational overtones that absorb at telecommunication wavelength of 1550 nm.

Several potentially conducting polymers, optically nonlinear polymers, and biomaterials contain heterocyclic structures. Reduction of the energy band gap of a conjugated polymer is a topic of considerable interest due to the possible elimination of doping in the preparation of highly conductive polymers. Control of the energy gap value of a polymer by molecular design could modify its optical, electronic and optoelectronic properties. Thiadiazoles and their derivatives are the structural basis of some of these polymeric materials. The results of the calculation of the HOMO-LUMO gap, the dipole moment and polarizability of thiadiazole oligomers in vacuo and in the presence of solvents are reported. The calculations are based on density functional theory using a specially tailored model chemistry. The potential utility of these materials for the development of chemical sensors is discussed.

Six zinc phthalocyanines with peripheral propanethio or p-methylbenzenethio groups, namely 1,8,15,22-tetrapropanethiophthalocyaninatozinc(II) (1), 1,8,15,22-tetra(p-methylbenzenethio)phthalocyaninatozinc(II) (2), 2,9,16,23-tetrapropanethiophthalocyaninatozinc(II) (3), 2,9,16,23-tetra(p-methylbenzenethio)phthalocyaninatozinc(II) (4), 2,3,9,10,16,17,23,24-octapropanethio phthalocyaninatozinc(II) (5), 2,3,9,10,16,17,23,24-octa(p-methylbenzenethio) phthalocyaninatozinc(II) (6) were synthesized for optical limiting study at 532 nm (pulse duration: 5 ns, repetition rate: 20 Hz). All of the compounds exhibited good optical limiting property when measured in dichloromethane solution in a quartz cell (pathlength: 1 mm, linear transmission: 75 %). The limiting thresholds (Fth, T/T₀ = 0.5) of these metal phthalocyanines were found to be 0.91, 1.1, 0.38, 0.5, 0.18, 0.15 J cm^-2 from complexes 1 to 6, respectively. The difference in their optical limiting performance can be attributed to their different ratio between excited state and ground state absorption cross section (σ_ex/σ_g), as demonstrated by Z scan measurements. C₆₀ and (t-Bu)₄PcInCl, benchmark optical limiting materials at 532 nm, were measured under the same conditions for comparison.

We present experimental and theoretical results on the development of a tunable bandstop and bandpass optical filter. The filter is based on Bragg grating technology in an organic electro-optical polymer. Wavelength tuning is achieved electrically by the electro-optic effect.