Joseph Zyss

Optically written solid-state lasers with broadly tunable mode emission based on improved poly (2,5-dialkoxy-phenylene-vinylene)

We report an optical written distributed feedback (DFB) structure with broadly and continuously tunable mode emission (Δλ=30u2009nm) based on polycondensation-type poly[2methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH–PPV). In a Lloyd-mirror configuration we realize first-order feedback by dynamic photoinduced in-plane gratings, which can also be imprinted permanently. This technique is a versatile fabrication tool for polymeric DFB laser structures while also providing an efficient method to probe the lasing performance of organic solid-state laser materials. Furthermore, features of the photoinduced absorption spectra of improved MEH–PPV indicate favorable material properties towards further homopolymer solid-state laser applications.

Organic surface emitting laser based on a deep-ultraviolet photopolymer containing thiocyanate groups

Gratings for laser applications are being optically recorded in poly(styrene-co-4-vinylbenzyl thiocyanate) (PST-co-VBT) by deep-ultraviolet lithography (λ<300u2009nm). The gratings writing configuration is based on interference patterning of this holographic material. Grating structures can be further stabilized and modified by selective amine reaction from the gas phase. Gratings based on refractive index contrast (Δn∼+0.02) and on thickness modulation (Δd up to 70 nm) are obtainable from this photoreactive polymer. Holographically recorded structures in films of PST-co-VBT doped with a laser dye are designed for second order distributed feedback operation resulting in low threshold organic laser devices (wL,th=0.25u2009μJu200acm−2) with laser emission output (TE-mode: λL=632u2009nm) directed perpendicular to the film plane.

Quantum and tensorial modeling of multipolar nonlinear optical chromophores by a generalized equivalent internal potential

The equivalent internal field model, originally developed for linear one-dimensional chromophores, is extended to three-dimensional multipolar chromophores. The extension requires two generalizations to the model. First, the equivalent internal field must be generalized to an equivalent internal potential. Second, all tensor components of the hyperpolarizability must be taken into account. A general formalism is developed for analyzing the hyperpolarizabilities induced by application of various internal potentials to a molecular skeleton, assuming the hyperpolarizabilities are linearly related to the internal potential. This formalism utilizes a symmetry analysis, along with quantum chemical calculations done here with the Huckel, Pariser–Parr–Pople and intermediate neglect of differential overlap (INDO) Hamiltonians and using single-configuration interaction theory. The formalism is applied to and tested on the benzene molecular skeleton. The hyperpolarizability is found to be linearly related to the int...

Opto-electronic oscillator: Applications to sensors

Optoelectronic oscillators (OEO) have been studied since many years now, the research activities being oriented towards the improvement of the oscillator. In this paper the using of an OEO as a sensing system based on the high sensitivity of its oscillation frequency to the fiber length is demonstrated. A slope of -75 kHz/mm has been obtained by tuning the length of a free space path inserted in the optical loop. An accuracy of 0.54% by measuring of the refractive index of a Plexiglas plate has been recorded. Other sensing structures are also proposed.

Orientation and nonlinear optical properties of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene crystals on nanostructured poly(tetrafluoroethylene) substrates

The growth of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) crystals on nanostructured poly(tetrafluoroethylene) (PTFE) substrates has been investigated by means of x-ray, micro-FTIR (Fourier-transform infrared) and nonlinear optical ellipsometry techniques. Two types of structural arrangements were identified, depending on growth conditions. In both cases, the (001)DAN plane contacts the (100)PTFE substrate plane. The major difference between both types of samples lies in the degree of azimuthal orientation at the interface. For thin samples (thickness 1u200aμm) are characterized by a uniaxial orientation with an isotropic random distribution in the plane of the layers. The comparison between various techniques used in this study to characterize the obtained thin films showed a remarkable agreement. In this context, ...

Controlling the directional emission of holey organic microlasers

The far-field pattern of stadium-shaped organic microlasers is strongly modified by introducing circular air vacancies within the cavity, so as to control it in a predictive way. Experimental results are in good agreement with geometrical optics predictions whereas spectral properties of emission are investigated to improve the understanding of the lasing modes.

Orientation and nonlinear optical properties of N-4-nitrophenyl-(L)-prolinol crystals on nanostructured poly(tetrafluoroethylene) substrates

Thin crystalline films of N-4-nitrophenyl-(L)-prolinol (NPP) were grown on nanostructured highly oriented poly(tetrafluoroethylene) (PTFE) substrates. Depending on the growth conditions, two types of crystalline orientation were observed. Thinnest samples ( 1 μm) could be obtained from deposition–annealing procedures and exhibit a (101)NPP planar orientation but with a lack of azimuthal orientation. The full characterization of these various samples was performed by analysis of x-ray diffraction data obtained in θ–2θ and grazing incidence geometry, the latter being used to determine the azimuthal orientation. Furthermore, the proposed orientations were fully consistent with the nonlinear optical (NLO) properties of the layers, deduced from optical second harmonic generation measurements. The com...

Stabilization of the bias point of an electro-optic modulator based on polymer material

Electro-optic modulators based on polymer material are very promising devices because of the expected very high modulation rate and low cost fabrication process. These modulators are mainly based on Mach-Zehnder structure, but phase modulators associated to polarizer and analyzer can also be used. Until now there are no real devices commercially available. One of the problems concerns the temperature stability. Because of the optical power of the laser beam and the absorption of the polymer material used for the optical waveguide there is a slight temperature evolution of the modulator leading to a change in the bias point of the modulator and then to a slow drift of the bias point leading to a dissymmetry of the optical modulated signal. This evolution can be compensated by adding a small DC value to the voltage applied to the electrodes. A control loop has been designed and tested in order to stabilize the bias point of the modulator. This loop acts as a synchronous detection with a low frequency modulation at 500 Hz and a practical detection at 1 kHz. By this way it is in fact the first order derivative of the signal which is stabilized leading to the signal symmetry control. This low frequency signal can be added without any problem to the informative modulating signal. By using this control loop the modulator can be used for a very longer time than without it. Of course a temperature control of the modulator by a Peltier effect module should also be implemented for a better and complete stabilization.

Out-of-plane modes in three-dimensional Fabry-Perot microlasers

Microlasers are involved in a broad range of devices for numerous research applications. However, the mode structures of three-dimensional microlasers without rotational symmetry are largely unexplored. Previous studies of such cavities revealed lasing modes exclusively localized on periodic orbits in the plane parallel to the substrate, which is to say that the associated momentum vectors are concentrated in the plane. In this paper, we characterize three-dimensional, polymer-based Fabry-Perot (i.e., ribbon-shaped) microcavities and demonstrate that such cavities exhibit modes with momentum vectors out of the substrate plane. These results constitute a proof-of-principle and motivate follow-up studies with more complex three-dimensional geometries.Microlasers are involved in a broad range of devices for numerous research applications. However, the mode structures of three-dimensional microlasers without rotational symmetry are largely unexplored. Previous studies of such cavities revealed lasing modes exclusively localized on periodic orbits in the plane parallel to the substrate, which is to say that the associated momentum vectors are concentrated in the plane. In this paper, we characterize three-dimensional, polymer-based Fabry-Perot (i.e., ribbon-shaped) microcavities and demonstrate that such cavities exhibit modes with momentum vectors out of the substrate plane. These results constitute a proof-of-principle and motivate follow-up studies with more complex three-dimensional geometries.

Strong electro-optic effect in self assembled peptide nanofibers

Low-cost biocompatible nanomaterials with opto-electronic properties are highly desirable as they may open avenue onto new biomedical imaging or sensing technologies. It was recently unveiled that short peptides self-assemble into various micro- and nano-structures including tubes, tapes and fibrils. These structures were found to possess striking mechanical, electrical and optical properties, which are rarely seen in organic materials. Here, we focus on the electro-optic (EO) properties of di- and tri-phenylalanine self-assembled peptide fiber structures and characterize them by using a home built EO phase microscope (PLEOM). This prototypal set-up is based on a highly sensitive interferometric scheme allowing to detect electric-field driven optical phase shifts at the focal point of the microscope objective. The Pockels effect requires a breaking of centro-symmetry, which is intrinsic to the ferroelectric phase in oxide crystals or to molecular crystals of adequate symmetry, or also in statistically oriented molecular assemblies such as biological tissues or membranes.