General Approach for the Sensitivity Analysis and Optimization of Integrated Optical Evanescent-Wave Sensors

The optimization of integrated optical evanescent-wave sensors is dual. For optimal performances, we require waveguides with both maximal sensitivity to the measurand, the quantity intended to be measured, and minimal sensitivities to perturbations. In this context, fully numerical approaches are extremely powerful, but demand huge computer resources. We address this issue by introducing a general and efficient approach, based on the formal derivation of analytical dispersion equations, to express and evaluate all waveguide sensitivities. In particular, we apply this approach to rectangular waveguides, to discuss its accuracy and its use within sensitivity optimization procedures

Intramolecular Cooperative Effects in Multichromophoric Cavitands Exhibiting Nonlinear Optical Properties

We report on the design, synthesis, and characterization of a new class of multichromophoric cavitands based on resorcin[4]arenes. The novel compounds have exhibited high values of second-order nonlinear optical (NLO) properties, as evidenced by electric-field-induced second harmonic generation (EFISHG) measurements. Theoretical calculations indicate the presence of edge-to-face T-shaped interactions between the aromatic building blocks within these multichromophoric systems, which is further supported by the detection of hypsochromic shifts in UV-vis and upfield aromatic chemical shifts in 1H NMR. We proved for the first time that the gain in the quadratic hyperpolarizabilities of multichromophoric NLO macrocycles, originating from the near parallel orientations of the subchromophores, can be partially suppressed if the distance between the dipolar subunits falls into a specific range, where intramolecular cooperative and/or collective effects are operative. Our finding will contribute to the better understanding of the phenomenon of cooperativity in new molecular materials with promising NLO properties. (Figure Presented). © 2015 American Chemical Society

Micro-résonateurs en anneau pour la détection et l’identification de polluants

Parmi les capteurs optiques visant la détection d’espèces chimiques ou biologiques, les dispositifs basés sur des microrésonateurs présentent un intérêt spécifique: ils n’ont pas besoin de marqueurs fluorescents, et leur fabrication est peu coûteuse. Le présent article décrit un capteur de ce type, basé sur des guides en anneau immergés dans un circuit microfluidique, et donne une illustration de ses performances pour la détection d’ions lourds dans l’eau potable