Tube hydroforming is a relatively new technology compared to conventional stamping. Thus, there is no large “knowledge base” that can be utilized for process and die design. To remedy this situation, considerable research is now being conducted by various institutions on significant aspects of tube hydroforming technology, including material selection, friction, pre-form design, hydroforming process and tool design, die materials and coatings. ERC/NSM is also conducting R&D in tube hydroforming in association with its industrial partners. This paper summarizes some of the early results in hydroforming of low carbon steel and aluminum alloy 6061-T9 tubes.

Organic materials hold a large promise for second- and third-order nonlinear optical and fast electro-optic applications due to the large nonlinearities of the basic molecular units and the almost purely electronic origin of the nonlinearity. We here discuss the new development in this field with respect to molecules, polymers, and molecular crystals.

We give an overview of the current status of research in the field of molecular crystals with respect to frequency-conversion, electro-optic modulation, and photorefractive effects. Applications of organic materials for nonlinear optics will depend on the development of waveguide devices and bulk crystals. Up to now the most advanced integrated optical organic devices use polymers. Thin crystalline films would also be very attractive if suitable techniques for high quality film deposition would become available. Organic molecular beam epitaxy offers new possibilities for fabricating low loss waveguides based on crystalline materials.

Polarization microscopy is a tool to investigate Langmuir monolayers in situ on a water surface as a function of environmental parameters such as lateral pressure, temperature, pH and concentration of contaminants, compression speed, and solvent. An anisotropically reflecting monolayer domain alters the polarization state of the reflected light and will have an orientation-dependent observable intensity. The contrast between domains of different orientation in such a film can be enhanced significantly when either the polarizer or analyzer is slightly rotated from the crossed position. The contrast between differently oriented domains is very large for molecules that have strong absorption. Domains in such films can be observed with the unaided eye. Staining of the sample is not required. Lateral resolution near Abbe's limit is obtained. A theory is developed to describe the effects. The theory is verified by analyzing the reflection from both a birefringent crystal and Langmuir monolayers of a molecule with anisotropic polarizabilities. Applications of the method to investigate monolayers are discussed. The described technique reveals information on the orientation of the polarizability axes of the domains or structures in a film and on the range and defects of orientational order within monolayers.

Undoped single crystals of the organic electro-optic material 4'-nitrobenzylidene-3-acetamino-4-methoxyaniline were found to show photorefractive effects owing to light-induced charge separation. In two-wave-mixing experiments, beam-coupling gains as high as 2.2 cm(-1) and response times as low as 8 s at writing intensities of 130 mW/cm(2) were measured at a wavelength lambda = 514.5 nm. An analysis of the experimental data shows that the beam-coupling gain is limited by the electro-optic response of the material, while the response time is characterized by a large optical absorption and a low quantum efficiency for carrier generation.

The electro-optic properties of 2-cyclooctylamino-5-nitropyrdine and 2-(N-prolinol)-5-nitropyridine single crystals have been evaluated. The dependence of the electro-optic coefficients on the optical wavelength and the frequency of the applied electric field was determined. Enhancements of these coefficients near acoustic resonances were observed and are discussed in terms of elasto-optic contributions. We propose a simple expression for estimation of the limiting values of electro-optic and nonlinear-optical coefficients. In addition, the wavelength dependence of the electro-optic figure of merit for organic and inorganic materials is estimated.

Photorefractive, doped (greenish) 2-cyclooctylamino-5-nitropyridine (COANP) crystals were obtained from a [TCNQ]22- enriched, supercooled melt. Growth upon fully immersed or pulled, c-oriented seeds produced either triangular plates or nearly an isometrical habitus, respectively. When using cut, polished and etched c-plates, growth of pure or doped COANP was observed only at the pyroelectric (-) end of the c-axis (DELTAT > 0). The photorefractive saturation diffraction efficiencies ranged from 0.1-1%, writing times were in the order of 10 min at 100 MW/cm2.

Electro-optic effects in single crystals of 2-cyclooctylamino-5-mitropyridine and 2-(N- prolinol)-5-nitropyridine have been investigated. The measured wavelength dependence of the electro-optic coefficients can be well explained with the quantum-mechanical two-level model. Enhancements of these coefficients near acoustic phonon resonances of up to a factor of 25 were observed when scanning the modulation frequency of the applied electric field. A comparison between measured second-order polarizabilities and electro-optic coefficients revealed that optic phonons may still contribute considerably to the electro-optic effects in the investigated molecular crystals. A simple expression to estimate the limiting values of electro- optic coefficients is proposed and compared with values of known molecular crystals.

Dissolving ⋍ 1000 ppm (1 ppm ≡ 1 μ mol / mol ) 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a superheated melt of 2-cyclooctylamino-5-nitropyridine (COANP) leads to formation of mainly [TCNQ] −2 2 that is incorporated into the COANP crystal lattice by supercooled melt growth at supercoolings smaller than ΔT ⩽ 0.5 − 1.5° C . Obtained doped COANP crystals show an extra optical absorption at λ max ⋍ 650 nm and are photorefractive. The found photorefractive effects are most probably induced by the presense of ∼ 50 ppm [TCNQ] −2 2 .

Single crystals of N-(4-nitro-2-pyridinyl)-phenylalaninol [CA index name (S)-beta-((5-nitro-2-pyridinyl)-amino)-benzenepropanol, CA registration number 115416-53-0] were grown from solution. The crystal structure was determined by x-ray analysis: space group P2(1), a = 11.791 angstrom, b = 6.032 angstrom, c = 9.959 angstrom, beta = 100.55-degrees, Z = 2. The refractive indices were determined in the spectral range of 470 to 1320 nm with an interferometric and a conoscopic method that are explained in detail. The highest nonlinear-optical coefficient was d23 = 31 pm/V. The nonlinear-optical properties are discussed in terms of crystalline structure and molecular hyperpolarizabilities.

For the first time photorefractive effects have been observed in 2-cyclooctylamino-5-nitropyridine (COANP) single crystals doped with 7,7,8,8-tetracyanoquinodimethane (TCNQ). Light induced refractive gratings with diffraction efficiencies up to 0.1% have been measured. The results of holographic and beam coupling experiments for different light polarizations indicate that the effect is based on a light induced charge separation and a refractive index change due to the electron-optic effect of the resulting space-charge field. It is demonstrated that photoabsorption or photo chemical refractive index changes can be excluded as mechanisms for the observed effects.

Photorefractive effects (due to electro-optic index change driven by photoinduced space-charge fields) have been found in a wide range of inorganic materials such as LiNbO 3 , KNbO 3 , Bi 12 SiO 20 , BaTiO 3 , GaAs, InP:Fe and others. To our knowledge, no such effects have been reported yet for an organic crystal. In this paper we report the observation of photoinduced gratings in an electro-optic molecular crystal which has been intentionally doped to induce photorefractive properties.

A method of growing high quality 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) single crystals is presented. Crystal plates with dimensions of up to 10×5×2 mm3 were produced and optically characterized. The transparency region extends from 485 to 2270 nm. Large birefringence and strong dispersion of the refractive indices were measured allowing two branches of type I and two of type II phase-matched second-harmonic generation. From effective second-order nonlinear optical susceptibilities measured along the branches all nonlinear susceptibilities were evaluated, the highest being d23 =(50±15) pm/V.