Near infrared two-photon self-confinement in photopolymers for light induced self-written waveguides fabrication

We present the fabrication of single mode light induced self-written waveguides using two-photon absorption in photopolymers. The measurements are compared to the finite element method simulation of the propagation and demonstrate that two-photon process leads to the confinement of light

Light induced self-written waveguides interactions in photopolymer media

We present experimental and theoretical study of the interaction of Light Induced Self-Written (LISW) waveguides in photopolymers. We show that the diffusion of the monomer controls the refractive index distribution. Consequently it influences the interaction between the LISW channels allowing the observation of anti-crossing behavior or the propagation of an array of non interacting LISW waveguides

Polarization state studies in second harmonic generation signals to trace atherosclerosis lesions

We have performed multi-photon image reconstructions as well as polarization state analyses inside an artery wall affected by atherosclerosis to investigate the changes in collagen structure. Mice, either healthy or affected by spontaneous atherosclerosis, have been used for this purpose. A two-photon imaging system has been used to investigate atherosclerotic lesions in the ascending aorta of mice. Second harmonic imaging has been performed alternatively on healthy samples and on affected region. The reconstructed images show that the spatial distribution of the collagen network seems disorganized by the disease. The polarization state studies reveal however that the apparent disorganization of the collagen is related to its spatially diffuse distribution and that the internal structure of the collagen fibers is not affected by the disease. In addition, a theoretical simulation of the second harmonic polarization states shows that they are consistent with the known 3D structure of the collagen network

Sum-frequency generation in sol-gel material doped with binaphthol

A sum-frequency imaging system is used to investigate optical activity in a sol-gel material doped with the chiral molecule binaphthol. We show that this material can be optically structured to embed information that can be retrieved by sum-frequency

Solvent-free fluidic organic dye lasers

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green-and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Forster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors

Dynamics of laterally coupled semiconductor lasers: transition to chaos

A method for the investigation of the dynamics of two semiconductor lasers, grown side-by-side on the same wafer to enhance the lateral optical coupling, is presented. Using steady state analysis, parameter regimes of relevant dynamics are identified. This is completed by a spectral analysis, were two routes to chaos are implicated. Finally, we confirm the calculations by showing an avoided crossing type of behavior for the coupling strength

Understanding the twin-stripe diode laser : a multimode perspective

A multimode model is necessary to describe the behavior observed in a twin stripe diode laser. We will use a single-stripe version of the device to calibrate the parameters enabling the model to be used in the description and analysis of the twin-stripe lasers

Beating photo-degradation in sum-frequency imaging of chiral organic media

Sum-frequency generation from chiral bulk media holds the promise of a powerful tool in the investigation of biological as well as artificial materials containing optically active elements. Since this technique is based on a nonlinear optical effect, the high intensities of the illuminating light sources may induce spurious artifacts. Using simple conjugated chromophores, we demonstrate that multi-photon induced irreversible photolysis may be avoided while keeping undiminished levels of sum-frequency signals. In addition we show that the concurrent multi-photon induced luminescence may provide complementary means of imaging samples. (C) 2015 Published by Elsevier B.V.(Honorat

Syntéza, fotofyzikální a nelineární optické vlastnosti lineárních push-pull systémů na bázi [1,2,5]oxadiazolo[3,4-b]pyrazin

A series of D-pi-A chromophores based on [1,2,5]oxadiazolo[3,4-b]pyrazine electron-withdrawing group has been designed. The influence of the pi-conjugated linker (1,4-phenylene and 2,5-thienylene) and the amino-electron-donating group (diphenylamino and carbazol-9-yl) was studied by cyclic voltammetry, UV-Vis and emission spectroscopy. The second order nonlinear optical properties were also studied using the electric field induced second harmonic generation (EFISH) method. The experimental results have been rationalized by theoretical DFT calculations.Byla připravena série D-pi-A chromoforů na bázi elektronakceptorního skeletu [1,2,5]oxadiazolo[3,4-b]pyrazinu. Prostřednictvím cyklické voltametrie, UV-Vis a emisní spectroskopie byl studován vliv pi-konjugovaného linkeru (1,4-fenylen and 2,5-thienylen) a elektrondonorního substituentu aminového typu (difenylamino and karbazol-9-yl). Experimentální data byla konfrontována s výsledky DFT kalkulací

Role of the Acceptor in Tuning the Properties of Metal [M(II) = Ni, Pd, Pt] Dithiolato/Dithione (Donor/Acceptor) Second-Order Nonlinear Chromophores: Combined Experimental and Theoretical Studies

The mixed-ligand complexes [M­(II)­(Et₂dazdt)­(mnt)] (M = Ni, <b>1</b>; Pd, <b>2</b>; Pt, <b>3</b>) [Et₂dazdt = <i>N</i>,<i>N</i>′-diethyl-perhydrodiazepine-2,3-dithione; mnt = maleonitrile-2,3-dithiolate] have been prepared and fully characterized. X-ray diffractometric studies on <b>1</b>–<b>3</b> (the structure of <b>1</b> was already known) show that the crystals are isostructural (triclinic, <i>P</i>–1), and two independent molecular entities are present in the unit cell. These entities differ in the orientation of the ethyl substituents with respect to the epta-atomic ring. In the C₂S₂MS₂C₂ dithiolene core the four sulfur atoms define a square-planar coordination environment of the metal where the M–S bond distances involving the two ligands are similar, while the C–S bond distances in the C₂S₂ units exhibit a significant difference in Et₂dazdt (dithione) and mnt (dithiolato) ligands. <b>1</b>–<b>3</b> show in the visible region one or two moderately strong absorption peaks, having ligand-to-ligand charge-transfer (CT) character with some contribution of the metal, and show negative solvatochromism and molecular quadratic optical nonlinearity, which was determined by the EFISH (electric-field-induced second-harmonic generation) technique. These complexes are redox active and show two reversible reduction waves and one irreversible oxidation wave. Theoretical calculations based on DFT and TD-DFT calculations on complexes <b>1</b>–<b>3</b> as well as on [Pt­(Bz₂pipdt)­(mnt)] (<b>4</b>) and [Pt­(Bz₂pipdt)­(dmit)] (<b>5</b>) highlight the factors which affect the optical properties of these second-order redox-active NLO chromophores. Actually, the torsion angle of the dithione system (δ₂) inversely correlates either with the oscillator strengths of the main transition of the complexes or with their beta values. The high beta value of <b>5</b> can be attributed both to its lowest torsion angles and to the extent of the π system of its dithiolate ligand, dmit