The objective of the present work is to investigate the thermo-optical (TO) properties of the relaxor-type ferroelectric
sodium-bismuth titanate (SBT) single crystals as a function of temperature, using the thermal lens and optical second
harmonic generation (SHG) techniques with the emphasis on the TO response near the phase transitions (PT).
Symmetry-forbidden SHG signals above 538 K in the [00l] cut SBT crystal are detected. The signals are related to the
coexistence of the tetragonal and rhombohedral phases. Heating of the uniaxial strain poled SBT crystal revealed
remarkable changes of the TO signal near the successive PT.
Investigations on the laser-induced reduction of advanced ceramic materials, including high-temperature supercondcutive (HTSC) ceramics, are presented. Here the oxygen content of the material is locally decreased by CW YAG:Nd laser irradiation in H<sub>2</sub> atmosphere. Direct laser-written metallic stripes into the weakly conducting sample surface had been tested by standard 4-point-probe technique in He dewar. New data about resistance temperature dependences of 100% laser reduce dstripes of HTSC Y-Ba-Cu-O ceramics has been determined. Our experimental data are in good agreement with Matthiasen's law with respect ot laser-written electrodes as YCu<sub>3</sub> alloys. As for high resistive stripes in HTSC ceramics begin written into the surface under imcomplete reduction regime we have found similar resistance behavior to random network of Cu fine particles connected 2D through thin oxide barriers. In the case of Bi-based HTSC ceramics a controversial picture takes place - low melting temperature of Bi oxide gives rise to segregation of Bi microspheres along the stripes corresponding to incomplete electroding. Although the laser-assisted surface alloying and metallization of bioceramics has been performed.
Thermal lens measurements on the thin films of ferrofluid located between the transparent indium-thin oxide (ITO) electrodes on glass substrate has been performed. In the presence of axial electric voltage we have observed suppression of characteristic far field patterns (rings) of thermal lens replaced by moving labyrinth structures. Critical value of the suppression field, for example in kerosene based ferrofluids - 13 kV/cm, and for ionic ferrofluids - 2,5 kV/cm, has been estimated.
In this paper nonlinear optical properties of indandione-1,3 pyridinium betaine (IPB) molecule and its novel amphiphilic derivatives have been studied. Hyper-Rayleigh scattering (HRS) has been used as a direct and accurate tool to determine effective hyperpolarizability (beta) of IPB derivatives dissolved in chloroform. Evaluation of hyperpolarizability gives an averaged values of (beta) from 140 multiplied by 10<SUP>-30</SUP> to 450 multiplied by 10<SUP>-30</SUP> esu. Disordering of molecular orientation for multilayer Langmuir-Blodgett films of compound C<SUB>17</SUB>-IPB has been studied by SHG techniques and discussed for different film thickness. It has been observed that orientation degree of the Z-type molecular structure increases significantly with the thickness of deposited LB film.
Here we report on the first, to our knowledge, direct experimental observation of giant thermo-optical mirror effect on the free surface of ferrofluid under He-Ne laser excitation. In our experiment a slightly focused laser beam of power in mW range is incident nearly normally to the surface, and a characteristic diffraction ring pattern has been observed in reflection mode. Concave surface deformation has been clearly observed at laser irradiated spot and has been explained in terms of lubrication theory approach for laser driven thermocapillary motion in thin layer of light absorbing fluid.
A method has been developed to determine the temperature distribution of ferroelectric surfaces and volumes. Based on the nonlinear optical effect of second harmonic generation (SHG) in highly nonlinear ferroelectric coating, demonstration of 2D thermosensing has been performed in the wide temperature range (77 K - 600 K). Physical concept of SHG thermal imaging, design of thermosensitive coating and experimental verification of the method has been discussed.