Organically modified silica: synthesis and applications due to its surface interaction with organic molecules.

An examination is made of the state of the art of nonlinear optical polymeric materials in view of their potential advantages. It is shown that these organic materials have many attractive features compared to LiNbO/sub 3/ and III-V semiconductors with regard to their use in integrated optic circuits, especially since the level of integration is ever increasing. Considering more specifically electro-optic devices, a description is given of some of the theoretical background and basic properties. These polymers have already demonstrated a very high and extremely fast electro-optic effect compared to LiNbO/sub 3/. It is also shown how low-loss waveguides can be fabricated by using easy techniques such as direct UV bleaching. The performance of phase modulators, Mach-Zehnder interferometers, and 2*2 space switches built with such polymers is already very promising. >

Integrated optic devices based on nonlinear optical polymers

Electrooptic properties of a ferroelectric polymer studied by attenuated total reflection

Preparation par reticulation photochimique dans l'etat polarise d'un poly(cinnamate de vinyle) dope par des cinnamates a proprietes optiques non lineaires. Le materiau obtenu presente une qualite optique excellente, des proprietes optiques non lineaires stables et des coefficients electrooptiques eleves

Novel photo‐crosslinked nonlinear optical polymers

Second‐order optical nonlinearity exists in a noncentrosymmetric crystal. We investigated a new molecular concept for noncentrosymmetric crystal structure. The Λ‐shaped molecules have been found to easily form noncentrosymmetric crystals by stacking along one direction. The configuration of Λ‐shaped molecules is close to an optimum condition for crystal phase‐matched nonlinearity. We demonstrate that methanediamine derivatives forming Λ‐shaped conformation are promising as efficient χ(2) materials.

New molecular design approach for noncentrosymmetric crystal structures: Lambda (Λ)-shaped molecules for frequency doubling

We describe the linear and nonlinear properties of a new polymer composite, which uses a ferroelectric PVDF copolymer host in which an optically nonlinear low-molecularweight guest is dissolved and subsequently aligned using a room-temperature poling process. We have measured the frequency-doubling coefficient d33 of these poled composites at 1-064/mi to be as high as 2-6 × 10?12m/V. In addition, we have shown that this material may be formed into waveguiding structures with an acceptable optical loss (?5dB/cm), as is needed in many signal processing systems.

Efficient frequency-doubling in a poled PVDF copolymer guest/host composite

Crystals of α‐[(4’‐methoxyphenyl)methylene]‐4‐nitro‐benzeneacetonitrile exhibit powder second‐harmonic generation (SHG) efficiencies under 1.06 μm irradiation several times that of 2‐methyl‐4‐nitroaniline. We have identified three distinct, solution‐grown polymorphs which show marked variation in SHG efficiency. Controlled transformation between these polymorphs can be made either solvent assisted or thermally. One polymorph shows a 25‐fold increase in SHG efficiency when the irradiation wavelength is changed to 1.32 μm while the others show a small or no increase.

Polymorphism and crystal‐crystal transformations of the highly optically nonlinear organic compound α‐[(4’‐methoxyphenyl)methylene]‐4‐nitro‐benzeneacetonitrile

A large and highly stable internal electric field has been measured in thin films of corona poled copoly(vinylidene fluoride - trifluoroethylene) by analysis of the alignment of coloured organic compounds (chromophores) dissolved as guests at low concentration in the host polymer These chromophores were designed to have both large electric dipole moments and high microscopic second order optical nonlinearities so that, when aligned in the internal field, they contributed to the small intrinsic nonlinearity of the poled host polymer The second harmonic coefficient of the mixture was found to be linear with the guest concentration and at 10% by weight to have a value of 26x10-12 m/V at 1064μm The coefficient of the films was found to be stable with time unless precipitation of the guest occured owing to an insufficient solubilty at the selected concentration This system is compared with thermopoled polymeric systems which have no stable internal electric field

Organic Polymer Films For Second Order Nonlinear Applications

The growth and characterisation of fibres containing a crystalline core of the nonlinear organic compound DAN in silica and higher refractive index capillaries is described. In addition to measuring the optical properties in transmission a method is described of measuring the sideways scatter from such fibres in order that a fuller understanding be made of factors which limit the achievement of very high SHG efficiencies.

Efficient Second Harmonic Generation From 2-(N,N-Dimethylamino)-5-Nitroacetanilide (DAN) Crystal Cored Fibres

The growth and characterisation of a number of organic single crystals, e.g. benzil, 2–methyl–4– nitroaniline and 2–N,N–dimethylamino–5–nitroacetanilide, in silica capillary has become fairly well established over recent years. [1–6 ] However the growth of these same compounds in glass capillary with a much higher refractive index than silica has received little interest. Crystal cored fibres, ccf's, in which there is a close match of the refractive index of the cladding to that of the core allows the possibility of fabricating single mode waveguides with useful dimensions for crystal growth. There is a better overlap integral between phase matched fundamental and second harmonic modes in a low moded structure than in a structure with more allowable modes and thus a rise in the conversion efficiency can be expected if the correct dimensions of waveguide are chosen. If a ccf of high conversion efficiency, 10% at 0.1 mW average power, could be made then the promise of fabricating an organic optical nonlinear device, e.g. parametric amplifier, might be realised. In this paper we will describe how the growth method adopted for silica clad organic crystals has been adapted for their growth in a range of Schott glasses which are better matched in refractive index, RI, than silica to the organic material. The linear and nonlinear optical properties of these crystal cored fibres will be given in terms of; the orientation of the crystal axes with respect to the fibre direction; the sideways scattering characteristics from defects; the throughput of the fundamental beam; the polarisation states of both the fundamental and the second harmonic outputs; and the overall efficiency of second harmonic generation.

The Growth of Organic Single Crystals in Glass Capillaries for Second Harmonic Generation

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