Stéphane Klein

One-step waveguide and optical circuit writing in photopolymerizable materials processed by two-photon absorption

Two-photon absorption process is known to be a convenient tool to create three-dimensional microstructures in photopolymerizable materials. In this context, we have fabricated stable optical waveguides. The features of these waveguides (in particular, transmission losses) have been compared to the results of numerical simulations. We have also demonstrated the possibility of connecting two optical fibers via a curved guide and to realize Y splitters. The technique allows one to fabricate operational integrated optical circuits in photopolymerizable resins.

Random laser action in organic film during the photopolymerization process

We report on transient laser action during the photopolymerization process in organic thin films of acrylate monomers doped with a laser dye. The emission spectrum was monitored over a period of time in the direction orthogonal to the incident laser beam which is kept at a constant intensity during the experiments. The emission spectra display the signature of laser action after a certain amount of polymerization. We have also recorded the intensity of fluorescence as well as of the amplified stimulated emission (ASE) using a photodiode. Our results confirmed that all the emission is guided by an increase of the refractive index resulting from the photopolymerization process. The spatial fluctuations in the density of the material are thought to act as micro-cavities leading to a random laser effect.

Electric properties of the water molecule in 1A1, 1B1, and 3B1 electronic states: Refined CASSCF and CASPT2 calculations

SummaryThe dipole moments and dipole polarizabilities of the 1A1, 1B1, and 3B1 electronic states of the water molecule have been calculated by using the CASSCF approach followed by the evaluation of the dynamic electron correlation contribution by the second-order perturbation scheme CASPT2. All calculations have been carried out in a specifically extended ANO basis set which accounts for the Rydberg character of the two excited states. In order to estimate the correctness and accuracy of the present data a scan over a variety of different active spaces for the CASSCF wave function has been made. The present results are superior to earlier CASSCF calculations, although their qualitative features remain essentially the same. The dipole moments in 1B1 and 3B1 states are predicted to be about 0.49 a.u. and 0.33 a.u., respectively, and have the opposite orientation with respect to the ground state dipole moment. The dipole polarizability tensors of the excited states are characterized by high anisotropy and are dominated by the in-plane component perpendicular to the symmetry axis. All their components are found to be about an order of magnitude larger than those of the ground state polarizability tensor. The excitation energy dependence on the choice of the active orbital space in the CASSCF reference function is also considered and the analysis of the present data concludes in the concept of what is called the mutually compatible active spaces for the two states involved in excitation. All CASPT2 results are in good agreement with the results of recent calculations carried out in the framework of the open-shell coupled cluster formalism. This agreement confirms the high efficiency of the CASSCF/CASPT2 approach to the treatment of the electron correlation effects.

Electric properties of the oxonium ion in its ground and two lowest excited states

Abstract The electric dipole moments and dipole polarizabilities of the oxonium ion have been calculated for the ground and two lowest excited states from the CASSCF and CASPT2 approaches. Two basis sets — an extended ANO and a smaller segmented basis — have been compared. The best values obtained at the CASPT2 level are μ = −0.5878 au (calculated at the centre of the nuclear charges), α ⊥ = 6.93 au and α ∥ = 5.66 au for the ground state, α ⊥ = 47.1 au and α ∥ = 10.8 au for the 1 A″ 2 excited state, α ⊥ = 45.9 au and α ∥ = 11.5 au for the 3 A ″ 2 excited state. To our knowledge, these are the first values available in the literature for the excited states.

Functionalized Photopolymers for Integrated Optical Components

ABSTRACT Photopolymeric matrices functionalized with optically active molecules are of special interest to elaborate low cost organic components for use in integrated optics. We have first studied the patterning of the optical properties using appropriate masks for the actinic light inducing the polymerization through a one-photon absorption process. The modulation of the refractive index can be used to make optical waveguides or quasi phase-matching structures. We have then studied, both experimentally and theoretically, the various growth forms of self-written waveguides created in the bulk of photopolymerizable resins under quasi-solitonic propagation conditions. By using another approach, we have taken advantage of the high spatial selectivity of the two-photon absorption procedure to design controlled optical polymerized pathways. As an example, we have realized fibers connections, Y-branch splittings, and finally, a passive Mach-Zehnder interferometer structure, opening the way to the fabrication of fully organic electro-optical modulators.

Colloid-based photonic crystal for dfb organic lasers and two-photon-induced polymerization for tunable DFB lasers

We propose two approaches for the fabrication of DFB lasers in photopolymerizable materials. The gratings are realized either by a periodic arrangement of nanospheres or through two-photon polymerization of a variable-step grating for tunable lasers

Photopolymerization techniques for the design of DFB organic lasers

We have investigated two approaches based on the use of photopolymerization techniques to create the corrugated surface, which is usually employed in the realization of organic distributed feedback (DFB) dye lasers. In the first approach, we use the strong capillary forces at the meniscus between a substrate and a colloidal sol to achieve highly ordered monolayered two-dimensional photonic crystal structures. In the second approach, we take advantage of the high spatial selectivity of the two-photon absorption process to design controlled polymerized pathways.

Integrated optical devices in organic materials photopolymerized via one and two-photon absorption

Two different approaches for the realization of permanent optical waveguides in photopolymers have been investigated. The first one is based on light-induced self-written waveguides (LISW), while the second one uses the technique of polymerization induced by two-photon absorption.

Solitonic guide and multiphoton absorption processes in photopolymerizable materials for optical integrated circuits

Up to now, most of the optical integrated devices are realized on glass or III-V substrates and the waveguides are usually obtained by photolithography techniques. We present here a new approach based on the use of photopolymerizable compounds. The conditions of self-written channel creation by solitonic propagation inside the bulk of these photopolymerizable formulations are analyzed. Both experimental and theoretical results of the various stages of self-written guide propagation are presented. A further step has been achieved by using a two-photon absorption process for the polymerization via a confocal microscopy technique. Combined with the solitonic guide creation, this technique allows to draw 3D optical circuits. Finally, by doping the photopolymerizable mixtures with push-pull chromophores having a controlled orientation, it will be possible to create active optical integrated devices.

Elaboration of optical integrated devices by multiphoton polymerization processes in doped photopolymers

Nonlinear optical photopolymers are of special interest for the realization of permanent integrated optical circuits via polymerization induced by one or two-photon absorption processes. In this context, we have explored the possibilities to create integrated devices by the 1D and 3D control of the photopolymerization. The various growth forms of self-written wave guides created in the bulk of photopolymerizable resins are presented and analyzed, both experimentally and theoretically. Under quasi-solitonic propagation conditions, the control of the refractive index during the photopolymerization progression allows the elaboration of wave guides over large distances (typically a few cm). We have also taken advantage of the high spatial selectivity of the two-photon absorption procedure for the design of controlled polymerized pathways. By using a two-photon confocal microscopy technique with a femtosecond laser source to activate the polymerization, we demonstrate how it is possible to create optical circuits in the bulk of doped photopolymers. Moreover, the permanent freezing of the orientation of push-pull chromophores embedded in the polymeric matrices opens up the possibility to design integrated circuits with different optical functions. Thus, by combining non linear optical properties and multi-photon polymerization technique, active 3D optical devices can be created in functionalized photopolymers.