Julien Zaccaro

Self-assembled monolayers of rigid thiols.

The preparation, structure, properties and applications of self-assembled monolayers (SAMs) of rigid 4-mercapto-biphenyls are briefly reviewed. The rigid character of the biphenyl moiety results in a molecular dipole moment that affects both the adsorption kinetics on gold surfaces, as well as the equilibrium structure of mixed SAMs. Due to repulsive intermolecular interaction, the Langmuir isotherm model does not fit the adsorption kinetics of these biphenyl thiols, and a new Ising model was developed to fit the kinetics data. The equilibrium structures of SAMs and mixed SAMs depend on the polarity of the solution from which they were assembled. Infrared spectroscopy suggests that biphenyl moieties in SAMs on gold have small tilt angles with respect to the surfaces normal. Wetting studies shows that surfaces of these SAMs are stable for months, thus providing stable model surfaces that can be engineered at the molecular level. Such molecular engineering is important for nucleation and growth studies. The morphology of glycine crystals grown on SAM surfaces depends on the structure of the nucleating glycine layer, which, in turn, depends on the H-bonding of these molecules with the SAM surface. Finally, the adhesion of PDMS cross-linked networks to SAM surfaces depends on the concentration of interfacial H-bonding. This non-linear relationship suggests that the polymeric nature of the elastomer results in a collective H-bonding effect.

Bulk cylinders and spheres: from shaping to the use for linear and nonlinear optics

Bulk crystals cut and polished as spheres or cylinders are unique tools for measuring the angular distribution of any linear or nonlinear optical property as well as for designing widely and continuously tunable parametric devices. The aim of this article is to describe the specific techniques of shaping such high quality samples, and their use in methods of optical measurements and devices that we implemented.

Frequency conversion in the acentric tetragonal nonlinear crystal NaI 3 O 8

We performed the first study of phase-matched second harmonic generation and difference frequency generation in the acentric nonlinear crystal NaI3O8. By fitting all the recorded phase-matching tuning curves, we determined the Sellmeier equations describing the wavelength dispersion of the ordinary and extraordinary principal refractive indices. We also measured the absolute value of the quadratic nonlinear coefficients and we calculated the conditions of supercontinuum generation in NaI3O8.

Phase-Matching, Sellmeier Equations and Nonlinear Coefficients of the New Nonlinear Crystal NaI 3 O 8

We performed the first study of phase-matching conditions in the new tetragonal crystal NaI3O8. We determined the refractive indices dispersion equations, calculated the tuning curves of optical parametric generation, and estimated the involved nonlinear coefficients.

Absorption and Fluorescence Singularities in the Nd:YCOB Monoclinic Crystal

We report the first measurements of angular distribution of absorption and luminescence in a biaxial monoclinic crystal. The patterns follow the index surface topology but main values are not in the optical frame.