[en] The study presented deals about both theoretical and experimental aspects of Surface Plasmons (SP) excitation. The principles of phenomenon rising are showed, together with the description of experimental devices needed to obtain such as excitation. The correlation between SP occurrence and electrochemical conditions is approached. (author)

[en] We report on calorimetric measurements carried out in an upgraded photopyroelectric setup enabling the determination of the frequency dependence of the specific heat and of the latent heat exchanged over first order transitions as well as the simultaneously determined nematic correlation length obtained from light scattering measurements. It has been applied to the study of the Nematic-Isotropic transition of 8CB liquid crystal confined in a silica nanoparticle network, where the specific heat shows a double peak structure.

[en] The advanced understanding of the complete degradation phenomena is crucial in order to develop robust optics for FEL. Under very harsh Synchrotron Radiation conditions, results show that multiscale wavelength damages could be observed, inducing local crystalline structure modifications of the high optical index material with a severe increase of the surface roughness

[en] Highlights: • ZnO nanorods were grown on Au and Ag films in aqueous solution by galvanic effect. • The method is prone to metal contamination which can influence the ZnO properties. • Iron doping improves the lattice matching between ZnO and the substrate. • Energy levels of point defects are lowered and the light emission is red-shifted. • Galvanic-induced nucleation starts and proceeds continuously during the growth. - Abstract: Dense arrays of vertically aligned ZnO nanorods have been grown onto either silver or gold seedless substrates trough a simple hydrothermal method by exploiting the galvanic effect between the substrate and metallic parts. The nanorods exhibit larger bases and more defined hexagonal shapes, in comparison with standard non-galvanic wet-chemistry synthesis. X-ray diffraction (XRD) shows that the iron contamination, associated with the galvanic contact, significantly improves the in-plane compatibility of ZnO with the Au and Ag cubic lattice. Photoluminescence (PL) measurements indicate that the contamination does not affect the number density of localized defects, but lowers their energy levels uniformly; differently, the band-edge emission is not altered appreciably. Finally, we have found that the ZnO hetero-nucleation by galvanic effect initiates at different times in different sites of the substrate area. Our results can be useful for the fabrication of high performance piezonanodevices comprising high-density metal-to-ZnO nanoscaled junctions without intermediate polycrystalline layers

[en] Highlights: • Photopyroelectric calorimetry performed while illuminating photocrhromic samples. • UV illumination induced photoisomerization of naphtopyran molecules in the sample. • Structure change induces strain in liquid crystals smectic phase. • Critical behavior over smectic nematic transition unchanged by illumination in 8S5. The effect of the UV light irradiation on the characteristics of the nematic-smectic-A and smecticA-smecticC phase transitions is investigated by the photopyroelectric calorimetric technique in mixtures of photochromic naphtopyran molecules with the $\overline{8}\text{S}5$ liquid crystal and the results are compared with those previously obtained in mixtures with the 8CB liquid crystal having a smaller nematic range. In $\overline{8}\text{S}5$, where the transition shows 3D-XY-like characteristics, the photoisomerization of the naphtopyran molecules to a more planar and elongated “open” form did not affect significantly the critical behaviour over the nematic-smecticA transition, while in 8CB it shifted it from a non universal to a the 3D-XY-like one. The results are discussed in terms of the effects caused by the naphtopyran molecules in their “open” form being able to be hosted in the smectic layers, while remaining confined between the planes when in their “closed” form. Similar arguments are used to also justify the dramatic increase of the transition temperature induced at the smecticA-smecticC phase transition by the UV irradiation of the $\overline{8}\text{S}5$ sample. Results obtained also in $\overline{8}\text{S}5$ -silica nanoparticles mixtures are also reported for comparison and discussed.

[en] A cryostatic setup is described to perform photothermal deflection measurements from room temperature to 77 K. The setup uses gaseous nitrogen as a medium where the photodeflection is produced. The ability of the system to work is demonstrated presenting some measurements of thermal diffusivity of high-temperature superconductor samples and of yttrium-iron garnets with variable aluminum content. copyright 1995 American Institute of Physics

[en] Highlights: • Photopyroelectric and adiabatic calorimetry enable to study p,p’-n-alkylazobenzenes. • The UV induced trans-cis isomerization influences the nAB phase transitions. • Upon cooling, 7AB phase transition sequence is: isotropic-nematic-crystal 2-crystal 1. • Trans-cis isomerization in 7AB and 8AB makes the intermediate mesophases disappear. A study of phase transitions of photochromic p,p’-n-alkylazobenzenes compounds was carried out by means of adiabatic scanning calorimetry (ASC) and photopyroelectric calorimetry (PPE) techniques, yielding accurately the temperature dependence of the enthalpy and of the specific heat capacity across the observed phase transitions, and the corresponding enthalpy of transition values. In addition, polarization microscopy imaging of the sample texture was performed together with the PPE calorimetric evaluations to establish the nature of the involved phases. By performing PPE calorimetric evaluations during UV irradiation of the samples, the influence of the photoinduced trans to cis isomerization of the nAB molecules on the occurrence of the phase transitions was assessed.

[en] We investigated second order optical nonlinearity of zinc oxide thin films, grown on glass substrates by the dual ion beam sputtering technique under different deposition conditions. Linear optical characterization of the films was carried out by spectrophotometric optical transmittance and reflectance measurements, giving the complex refractive index dispersion. Resistivity of the films was determined using the four-point probe sheet resistance method. Second harmonic generation measurements were performed by means of the Maker fringes technique where the fundamental beam was originated by nanosecond laser at λ=1064 nm. We found a relatively high nonlinear optical response, and evidence of a dependence of the nonlinear coefficient on the deposition parameters for each sample. Moreover, the crystalline properties of the films were investigated by x-ray diffraction measurements and correlation with second order nonlinearity were analyzed. Finally, we investigated the influence of the oxygen flow rate during the deposition process on both the second order nonlinearity and the structural properties of the samples