A novel Laponite-lithium iodate nanocomposite has been synthesized for nonlinear optical applications. The
elaboration starts with the addition of a lithium iodate aqueous solution to a colloidal suspension of Laponite
JS. Thin layers, elaborated using the dip-coating technique, form waveguides and the linear dependence between
the lithium iodate concentration and the refractive index and the control over the thickness allow one to optimize waveguiding properties. Waveguides show an attenuation of about 2 dB/cm and easily detectable second
harmonic generation. For the nonlinear effective coefficient a value of 1.6 pm/V has been measured. X-ray
structural characterization shows that after drying and heat-treatment between 150 and 200°C, lithium iodate
crystallizes in the matrix with the crystallite size ranging from 20 to 50 nm. Due to the natural dipole moment
of lithium iodate, the orientation of nanocrystals could be controlled using external electric field. The influence
of the orientation on the nonlinear optical properties has been determined and compared with the simulations
based on a matrix model considering the nanocomposite as a stack of linear and nonlinear 1D layers with fixed
or random orientation. A good agreement is achieved between the experiment and the simulation.
In recent years, a large amount of activity has been carried out searching new materials for second order non-linear optics. Nanostructured materials composed of a host matrix and optical active nanocrystals form a new part of this research field. Our present work consists in "doping" SiO2 matrices with 5 to 30% mass of LiIO3 nanocrystals. Indeed, α-LiIO3 is a compound known to be very efficient for second harmonic generation (SHG). This nanocomposite glass has been developped using sol-gel technics. Bulk samples have been first studied showing nanocrystallites with size ranging from 50 nm to 400 nm and second harmonic generation (SHG). Then thin layers have been elaborated using dip coating and spin coating technics. Being given that LiIO3 crystals present structurally a strong dipolar moment, non-linear optical properties could be enhanced using Corona
discharges to orientate nanocrystals. This paper relates the fabrication process and the structural and optical characterizations of bulk and thin layer material.
In an effort to provide synchrotron x-ray beamlines with improved monochromators, a new series of 111-oriented diamond crystals up to 50 mm2 large with thicknesses ranging from 67 micrometer to 175 micrometer was prepared, tested and found to be of very high quality. One sample appeared to be without any defects. Some linear defects were observed by topography on the other samples but without any consequences for the rocking curve width, except for one sample that revealed some mosaicity in part of its volume and could serve as variable flux/resolution monochromator. The rocking curve width exceeded sometimes the theoretical perfect crystal value by a couple of arcsec. Peak and integrated reflectivities were observed to be very close to the theoretical values for a perfect diamond crystal. For the first time, a diamond crystal was elastically bent to achieve sagittal focusing. Although the bending was not absolutely uniform, a spot size of 1 micrometer and gain factors exceeding one order of magnitude were obtained. These results showed that dispersion-free diamond double crystal monochromators of the classical type can be made.
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