Reversible recording medium based on optical storage of information, method of reversible recording on such a medium.

A reversible recording medium based on optical storage of at least one item ofinformation within a support material, includes at least one layer of support material having: base molecules able to take, in a local zone, a first collective state of molecules able to generate a first signal of second harmonic characteristic of this first collective state of molecules when excited by electromagnetic reading radiation; the base molecules having the first collective state of molecules able to transform, at least in part, into transformed molecules so as to pass to a second collective state of molecules when excited by electromagnetic writing radiation, the molecules having the second collective state of molecules able to generate a second signal of second harmonic characteristic of this second collective state of molecules when excited by the electromagnetic reading radiation. The molecules exhibit a molecular structure based on a coumarin skeleton of Formula (I)

Reversible Two-Photon Optical Data Storage in Coumarin-Based Copolymers

A functionalized polymer film allowing for a complete and straightforward second-harmonic generation (SHG)-assisted high-contrast writing?reading?erasing?writing sequence is proposed. The whole process is supported by the reversible photoinduced dimerization of a coumarin chromophore and enables efficient optical data storage that can be detected only by SHG imaging

Synthesis, characterization and photochemical properties of side-chain coumarin polymers

Date du colloque : 05/2008International audienc

Thermally induced crystallization, hole-transport, NLO and photovoltaic activity of a bis-diarylamine-based push-pull molecule

The synthesis of a molecule constituted of two diarylamine-based push-pull chromophores covalently linked via their nitrogen atom is described. Comparison of the electronic properties with the parent monomer shows that dimerization has negligible influence on the electronic properties of the molecule but exerts a dramatic impact on the capacity of the material to self-reorganize. Application of thermal annealing to thin films induces the crystallization under original morphologies, a process accompanied by a partial bleaching of the absorption in the visible range and by a huge increase of hole-mobility. X-ray diffraction data on single crystals reveal the presence of π-stacked organization with a non-centrosymmetric co-facial arrangement of the dipoles which leads to intrinsic 2nd order bulk NLO properties of thin films as evidenced by second harmonic generation under 800 nm laser light. The implications of this thermally induced crystallization on the photovoltaic properties of the material are discussed on the basis of preliminary results obtained on simple bilayer organic solar cells

(Super)Gelators derived from push-pull chromophores: Synthesis, gelling properties and second harmonic generation

The present work takes advantage of the self-assembly process occuring along organogelation, to organize Second Harmonic Generation (SHG) active chromophores. To do so, three push-pull chromophores endowed with a dodecyl urea chain were synthesized and characterized. Their organogelating properties were studied in a wide range of solvents. Despite similar architectures, these derivatives exhibit very different gelling properties, from supergelation to absence of gelling ability. The utilization of the Hansen solubility parameters allows for observing clear relationships between the gelled solvents and critical gelation concentrations. By evaporating the solvents from the organogels, xerogel materials were prepared and systematically studied by means of optical and electron microscopies as well as SHG microscopy. These studies demonstrate the critical role of the solvent over materials structuring and allow generalizing the approach exploiting organogelation as a structuring tool to spontaneously organize push-pull chromophores into SHG-active materials

Nonlinear Optical Response of Self-Assembled Molecular Corners

During the last years there is a growing effort in order to synthesize, functionalize and characterize modern molecular systems, which will have enhanced nonlinearities in order to be utilized in modern photonic applications. The nonlinearities are generally known to be significantly enhanced in systems which exhibit strong charge transfer within specially chosen moieties acting as electron donors or acceptors. Utilizing proper functionalization the charge transfer can be more enhanced by increasing the amount, as well as the mobility of the p-electrons of the systems. In this work we quantify the magnitude of the third order nonlinear susceptibility χ(3) of the TTF based molecular corners shown in Fig. 1, by the Degenerate Four Wave Mixing (DFWM) setup. Moreover by means of the Z-scan setup separate characterization of the nonlinear absorption of the systems is carried out. The advantage of these systems is that apart from their high nonlinearities can be combined in order to synthesize more complicated molecular systems like rotaxanes, catenanes etc

Changing gears to neutral in a polymorph of one-dimensional arrays of cogwheel-like pairs of molecular rotors

We report on a polymorph (2) of an amphidynamic crystal of molecular rods with two helical 1,4-bis(ethynyl)bicyclo[2.2.2]octane rotators where half of the rod-like molecules appear to be shifted with respect to their closest neighbours. This translation takes cogwheel-like pairs of rotators apart in the lattice in such a way that their motion becomes uncorrelated. This property is to be contrasted with the highly correlated motion found to govern the rotators in a recently-published polymorph 1 of the same material. As with polymorph 1, this motion is shown to take place independently of mutations in the handedness of the rotators and of the ‘mutamer’-induced second harmonic generation

Nonlinear absorption reversing between an electroactive ligand and its metal complexes

We present the nonlinear absorption investigation of an electroactive ligand and two ruthenium and iron metal complexes under 532 nm, 30 ps laser excitation, by the open aperture Z-scan technique. Significant nonlinear optical parameters have in all cases been measured, while the nonlinear attribute has been found to change from saturable to reverse saturable absorption between the initial ligand and its complexes