Ablation of Lithium Niobate through femtosecond nonlinear absorption

Femtosecond laser processing is a promising alternative technique for manufacturing photonic elements such as gratings, micro-holes, and microchannels in different type of transparent materials. The effect of the irradiation of commercial Lithium Niobate substrates with a Ti-Sapphire oscillator with repetition rate 82 Mhz, energy per pulse 20 nJ, pulse duration of 130 fs and an amplified Ti-Sapphire laser system with repetition rate 1 kHz, energy per pulse 1 mJ, and pulse duration of about 130 fs are compared. The investigation of microstructural modifications induced by femtosecond irradiation through optical microscopy and micro-Raman spectroscopy is reported

Microstructural modification of LiNbO3 crystals induced by femtosecond laser irradiation

In this work we report on the study of microstructural modifications induced by femtosecond laser irradiation on Lithium Niobate crystals by means of optical microscopy and micro-Raman spectroscopy

PLASMA-SPRAYED ZIRCONIA ELECTROLYTES

Zirconia-based electrolytes, stabilized either with yttrium oxide or calcium oxide, were prepared in 100 to 200 \ub5m thick layers by plasma spraying and densified by high-temperature vacuum sintering. The structure and the microstructure were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The results are compared with the data we obtained on the powders used for plasma spraying and on single crystals. In the zirconia-yttria system, dense and fully stabilized zirconia films with structural properties similar to the corresponding single crystals were obtained. On the other hand, cracks and deformations were observed on calcia-stabilized films. This phenomenon is explained by the dramatic increase of monoclinic phase content due to the preferential evaporation of calcium oxide which occurs during high-temperature vacuum sintering

Stoichiometry dependence of the electrooptic response of Lithium Niobate

We investigated the electrooptic response of a set of Lithium Niobate crystals with Li concentration ranging from off-congruent to stoichiometric. Two accurate techniques based on interferometry and ellipsometry were employed to measure the electrooptic coefficients. No evidence was found of a possible enhancement of the EO response in stoichiometric Lithium Niobate with respect to the congruent one. The EO response showed a weak dispersion in the wavelength range 532-1550 nm

Raman study of Ba0.7Ca0.23TiO3 single crystals

Congruently grown barium calcium titanate, Ba0.77Ca0.23TiO3 (BCT77/23) can be fabricated as high optical quality single crystals, possess large electro-optic coefficients and high holographic sensitivity making it excellent candidate for various photorefraction based applications. Another great advantage of BCT is that the tetragonal-ortorhombic phase transition, which is destructive in BaTiO3, is depressed in BCT 77/23. In the present work we report on Raman study of BCT 77/33 crystals have been performed in the temperature region between 420K-10K. To our knowledge, this is first Raman light scattering study of BCT 77/23. We believed to gain insight on the nature of the cubic-tetragonal ferroelectric phase transition (PT) in BCT 77/23, on the role of Ca admixture, and search manifestations of the possible low temperature tetragonal-orthorhombic PT has been reported in [4]. A special attention was paid to detailed studies of the low energy region 5 200 cm-1 and to temperature evolution of A and E components of the 15 modes. A detailed polarization analysis was performed. The integrated intensities and bandwidth are deduced from fitting analysis. The data regarding the cubic-tetragonal PT are in agreement with previous results about dielectric permittivity confirming the complex nature of these phase transitions. The Raman data at lower temperatures give no clear indications about the occurrence of the T-O PT, at least down to 10 K. In addition weak features around 100 cm-1 were found, which are not observed in BaTiO3 matrix and probably arising from the presence of Ca ions