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The effect of pressure on the structural, elastic, and thermodynamic properties of SrTe in both B1 (rocksalt) and B2 (CsCl-type) phases and the SrTe1−xCax alloys with Ca dopant concentrations at x = 0.16667, 0.20, 0.33333, 0.42857, 0.44444 and 0.50 have been investigated using the two new gradient-corrected functional developed by Perdew, J.P.; Burke, K.; Ernzerhof named Density-Gradient Expansion for Exchange in Solids (PBEsol) and generalized Wu–Cohen (WC), in a significant range of pressure from 0 GPa to 30 GPa. The structure parameters, elastic stiffness constants cij, the bulk modulus (B), Kleinman parameter (\( \xi \)), shear anisotropies Ashear are also determined. Furthermore, as reported in this study, the aggregate elastic modulus (B, G, E), Poisson’s ratio (ν) and the Lame’s coefficients (λ) are estimated. On the other hand, the ductility, brittleness, longitudinal, transverse sound velocities and the Debye temperature ΘD(T) are also obtained. Importantly, our results are in reasonable agreement with the available theoretical and experimental data. To the best of our knowledge, this is the first study of the effect of the composition on the properties of the SrTe1−xCax alloys which may encourage other works for the confirmation of the reported results.

In this work, the effect of pressure on the electronic band structure, partial density of states (PDOS), and the band gap of the four phases of ZnO, namely B4 (wurtzite), B3 (zinc-blende), B1 (rocksalt) and B2 (CsCl-type), has been investigated using the plane-wave pseudo-potential code CASTEP with three different schemes: the generalized gradient approximation (GGA) in the latter approach Perdew–Burk–Ernzerhof (PBE) with and without spin–orbit (SO) coupling, the new hybrid exchange–correlation functional named B3LYP functional and Hartree–Fock + Local Density Approximation (HF + LDA). These schemes are employed in order to treat the exchange–correlation effects. In addition, we will illustrate how the orbital motion of crystal electrons is affected by spin–orbit (SO) coupling. To our knowledge, this is the first theoretical study reported on ZnO using the B3LYP method. Our investigation shows that the increase of the pressure causes the nature of the band gap to change from direct to indirect. The mechanism responsible for this change of band structure is analyzed. The wide band gap of the B4 (wurtzite) phase at p = 0 as determined by the precedent methods is ∼3.221 and 3.222 eV (PBE) with and without spin–orbit (SO) coupling, respectively, 9.186 eV (HF + LDA) and 2.451 eV (B3LYP). The first two approaches provide the best agreement with the experiments. The band gap of B3 (zinc-blende), B1 (rocksalt) and B2 (CsCl-type) and the strong contribution of d orbitals of Zn atoms on the structure of the bands will be discussed. The SO coupling effect on the band structure for all phases is presented. This effect on the electronic properties of the various phases of ZnO in particularly for the B3 (zinc-blende), B1 (rocksalt) and B2 (CsCl-type) phases at high pressures are not well-known. The aim of this work is to improve the DFT band gap error by introducing different schemes and therefore this study is important for future experimental work on this potential semiconductor material. In this study we have shown the effect of SO coupling on the bands structure of ZnO as a function of pressure, and analyzed the mechanism of this effect. The understanding of spin–orbit coupling related phenomena is very important in both fundamental research and in applications of semiconductors systems.

The structural, electronic and vibrational properties of InN under pressures up to 20GPa have been investigated using the pseudo-potential plane wave method (PP-PW). The generalized-gradient approximation (GGA) in the frame of density functional theory (DFT) approach has been adopted. It is found that the transition from wurtzite (B4) to rocksalt (B1) phase occurs at a pressure of approximately 12.7GPa. In addition, a change from a direct to an indirect band gap is observed. The mechanism of these changes is discussed. The phonon frequencies and densities of states (DOS) are derived using the linear response approach and density functional perturbation theory (DFPT). The properties of phonons are described by the harmonic approximation method. Our results show that phonons play an important role in the mechanism of phase transition and in the instability of B4 (wurtzite) just before the pressure of transition. At zero pressure our data agree well with recently reported experimental results.

We report on the strong coupling between a Tamm plasmon mode and excitons from inorganic quantum wells. The sample is formed by an AlAs/GaAlAs Bragg reflector containing InGaAs QWs in its high refractive index layers, on top of which a thin silver film is deposited. Angle resolved reflectometry experiments at low temperature (77 K) show a clear anticrossing in the dispersion relations, evidencing the strong coupling regime. The Rabi splitting amounts to 11.5 meV. Emission from low and high energy Tamm plasmon/exciton polaritons is also demonstrated. Experimental data are in very good agreement with transfer matrix simulations.

We report the results of a theoretical study on the behaviour of the structural parameters and the pressure of transitions from B4 (wurtzite) to B3 (zinc-blende) phase, from B4 (wurtzite) to B1 (rocksalt) phase and from B3 (zinc-blende) to B1 (rocksalt) phase of GaN in a significant range of pressure from 0 to 100 GPa at T = 0 K. According to our knowledge, for the first time a theoretical study is driven until 100 GPa. The transition from B4 (wurtzite) to B3 (zinc-blende) phase is not reported in literature. For this reason the pressure of transition and the evolution of the structural parameters are estimated according to the corresponding pressure. The calculations are based on the ab initio plane-wave pseudo-potential Density-Functional Theory (DFT), within both the Generalized Gradient Approximation (GGA) and Local-Density Approximation (LDA) for the exchange and correlation potential. The calculated values of transition pressure, lattice parameters are in very good agreement with experimental results. A linear-response approach to the density-functional theory is used to derive the phonon frequencies and densities of states. Where, we discussed the contribution of the phonons in the instability of B3 (zinc-blende) phase.

We report on the strong coupling between surface plasmons and inorganic quantum well excitons. The sample is formed by a corrugated silver film deposited on the top of a heterostructure consisting of five GaAs/GaAlAs quantum wells grown by molecular beam epitaxy. Reflectometry experiments at low temperature (77 K) evidence the formation of plasmon/heavy-hole exciton/light-hole exciton mixed states. The interaction energies, deduced by fitting the experimental data with a coupled oscillator model, amount to 22 meV for the plasmon/light-hole exciton and 21 meV for the plasmon/heavy-hole exciton. Some particularities of the plasmon–exciton coupling are also discussed and qualitatively related to the plasmon polarization.

TiO 2 thin films were prepared by sol-gel method. The structural investigations performed by means of X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) showed the shape structure at T = 600 °C. The optical constants of the deposited film were obtained from the analysis of the experimentally recorded transmittance spectral data in the wavelength of 200–3000 nm range. The values of some important parameters of the studied films are determined, such as refractive index n and thickness d . In this work, using the transmission spectra, we have calculated the dielectric constant ( e ∞ ) for four layered TiO 2 films; a simple relation is suggested to estimate the third-order optical nonlinear susceptibility χ (3) . It has been found that the dispersion data obeyed the single oscillator of the Wemple–DiDomenico model, from which the dispersion parameters and high-frequency dielectric constant were determined. The estimations of the corresponding band gap E g , χ (3) and e ∞ are 2.57 eV, 0.021 · 10 −10 esu and 5.20, respectively.

Structural and elastic properties of InN in both B4 (wurtzite) and B1 (rocksalt) phases are studied over a wide range of pressures from 0 to 20 GPa at T = 0 K, using the density functional perturbation theory (DFPT) for the first time. Pressure dependencies of the total energy, structure parameters, elastic stiffness constants c ij , bulk modulus, Kleinman internal strain parameter, shear anisotropies and their relationship to elastic stability are also explored. In addition, the aggregate elastic modulus (B, G, E), Poisson's ratio (ν) and Lame's coefficients (λ) are estimated within the framework of Voigt–Reuss–Hill approximation for ideal polycrystalline InN aggregates, and thus the longitudinal and transverse sound velocities are obtained. We estimated the Debye temperature ΘD(T), energy E(T), entropy S(T), free energy F(T), and lattice heat capacity c v (T) as a function of temperature at null pressure for B4 (wurtzite) phase. Our results are in reasonable agreement with the available theoretical and experimental data for B4 phase. To our knowledge this is the first quantitative theoretical prediction of the B1 (rocksalt) that is still awaiting experimental confirmations.

A new clay-based nanocomposite has been developed for non-linear optical waveguiding applications. Thin layers are deposited on glass substrates by using dip coating technique from an aqueous solution made of a Laponite suspension mixed with a lithium iodate (LiIO3) aqueous solution. Transparent layers with waveguiding properties are obtained with an effective non-linear coefficient of about 1.4 pm/V for a 55% vol. LiIO3 composite. Control of nanocrystals orientation has been performed by applying an electric field with Corona discharge or deposited gold electrodes. Characterisation of nanocrystals orientation was done by Second Harmonic Generation (SHG) measurements and polarised light optical microscopy.

The present paper presents our work consisting of `doping' SiO2 sol–gel matrices with 5–30% mass of LiIO3 nanocrystals. Indeed, bulk α-LiIO3 is known to be very efficient for second harmonic generation (SHG). Bulk nanocomposite samples have been first studied showing nanocrystallites with size ranging from 50 to 400 nm and SHG. Then dip and spin coating methods have been used to build thin layers. Being given that LiIO3 crystals present structurally a strong dipolar moment, non-linear optical (NLO) properties may be enhanced using Corona discharges to orientate nanocrystals. This paper relates the fabrication process and the structural and optical characterizations of bulk and thin layer material.

International audience; In this article, the Raman signal of CdSe nanocrystals well dispersed in a very thin SiO2 film (20 nm) has been investigated by surface plasmon excitation in a resonant Raman spectroscopy experiment. In order to perform the excitation, the thin SiO2layer containing nanocrystals is deposited on a well-defined silver layer. The surface plasmon excitation increases the sensitivity of the Raman experiment, compared to the conventional setup, and allows the observation of a small number of nanocrystals (around 5000). The luminescence has also been measured and its dependence with the separation between the metal layer and CdSe nanocrystals is analyzed. In particular the quenching of the luminescence for thin film has been used to obtain only the Raman signal in resonant configuration.

We describe the first elaboration of carbon nanotube tips (CN-tips) by the sol–gel technique. The CN-tips consist of single carbon nanotubes (CNs) or bundles sheathed by a nanometric layer of TiO2 fixed to the apex of a W base tip and oriented along its major axis. The straight-forward method potentially permits low cost batch fabrication. Structural analysis has been realized by transmission electron microscopy (TEM). These CN-tips are interesting for applications in applied surface science such as field emission (FE) sources and near field microscopy probes. A first field emission study has also been carried out showing that the TiO2 layer does not block FE. Relatively stable emission at voltages usual to FE from CNs at up to 0.8 μA current were obtained.

International audience; We discuss attractive potentialities of the sol–gel process applied to planar microcavities with distributed Bragg reflectors (DBRs). This method is well known for its good flexibility and the optical quality of the thin films obtained. The DBRs are composed of alternated TiO2 and SiO2 thin films. One of the main problems of the sol–gel process is the stresses induced during the layers heat treatment leading to defects and cracks in the films. The study of these stresses shows that with the appropriate annealing temperature and duration of the firing process, the stress in the SiO2 layers partially compensates the stress in the TiO2 layers. DBRs and microcavities formed by 60 stacked layers have been elaborated in these conditions. The reflectivity of such sol–gel DBRs reaches 99.7%. The sol–gel DBRs are used to fabricate microcavities containing Eu3+ rare earth ions with a quality factor of approximately 1000.

Very thin ZrO 2 films (few nanometers) have been prepared by sol-gel process. These films were deposited onto a stack of a thin silver layer evaporated on a glass substrate for Surface Plasmons Resonance (SPR) experiments. The first aim of this work is to study the high densification of the sol-gel films followed by the refractive index and thickness accurate measurements at each step of the annealing procedure, using an optical set-up based on SPR. Secondly, SPR excitation coupled with micro-Raman experiment has also been performed to determine the thin films structure depending on layer thickness. Finally, Conventional Transmission Electron Microscopy (CTEM) and High Resolution (HRTEM) studies have been conducted to check and complete Raman spectroscopy results. A discussion compares the optical results and the Transmission Electron Microscopy observations and shows that ultra thin layers structure is strongly depends on films thickness.

In this paper we describe the properties of organic material in strong coupling with plasmon, mainly based on our work in this field of research. The strong coupling modifies the optical transitions of the structure, and occurs when the interaction between molecules and plasmon prevails on the damping of the system. We describe the dispersion relation of different plasmonic systems, delocalized and localized plasmon, coupled to aggregated dyes and the typical properties of these systems in strong coupling. The modification of the dye emission is also studied. In the second part, the effect of the microscopic structure of the organics, which can be seen as a disordered film, is described. As the different molecules couple to the same plasmon mode, an extended coherent state on several microns is observed.

The laponite films elaboration is based on the sol–gel process and dip-coating technique. The films are dried at 120°C and heat-treated at higher temperature up to 600°C without deterioration of their quality. Three micrometer thick and crack-free films are obtained in only one coating by dipping a substrate into a well-controlled viscous solution. By this way 9 μm high quality thick films have been prepared using three successive coatings and adapted heat treatment. These films exhibit light waveguiding properties. Differential thermal analysis (DTA) measurements conducted on the powder indicate water removal phenomenon at different annealing temperatures. These results are correlated with X-ray diffraction (XRD) analyses to explain preferential orientation and densification of the 600°C heat-treated layer. This structural behavior involves optical birefringence and refractive index increase of the film. Potentialities to use laponite films in planar optical waveguide field are presented.

International audience; In this paper we describe the modifications in the GaAs quantum well (QW) optical properties induced by the proximity of a metallic film. The formation of hybrid plasmon/exciton states composed of a mix of heavy-hole exciton/light-hole exciton mixed states is demonstrated with reflectometry experiments. Alternative surface modes, namely Tamm plasmons, can also induce hybridization with the QW excitons with Rabi splitting energy of 11.5 meV. Plasmonic Tamm states are interface modes formed at the boundary between a photonic structure and a metallic layer. These modes present both the advantages of surface plasmons and of microcavities photonic modes. A conventional lasing effect will also be described in Tamm plasmon structure containing QWs. Tamm plasmons can be spatially confined by structuring the metallic part of the system, thus reducing the size of the mode and allowing various geometries. Due to the relatively low damping and the versatility of the Tamm geometries, these modes are good candidates for a new type of lasers.

In this paper we present results on CdS nanocrystal (NC) formation in ZrO2 thin film grown by sol–gel process. Raman and waveguiding Raman scattering spectroscopies were applied to determine CdS nanocrystal precipitation in our films. RBS (Rutherford back scattering) and optical absorption spectroscopy were applied to determine CdS distribution homogeneity through the layer depth, NC size and dispersion. Thus we obtained low size dispersed CdS nanocrystals with preparation temperature controlled size. Moreover, Raman and high-resolution transmission electron microscopy (HRTEM) evidenced simultaneous correlated crystallisation of hexagonal CdS and tetragonal/monoclinic ZrO2 phases. We applied also light induced dynamic grating technique under high excitation conditions in order to analyse dynamic properties of nonequilibrium charge carriers in thin films.

Thin films of lead titanate were prepared by a chemically modified sol-gel process and dip-coating technique. The process was refined such that homogeneous crack-free films could be produced which showed excellent waveguiding properties. A 600°C heat treatment was required to obtain the crystallization of the PbTiO3 perovskite phase. The microstructure of the phases was studied using waveguide Raman spectroscopy and transmission electron microscopy. The film was composed of an upper layer of large perovskite grains (∽100 nm) on a lower lead content phase which appeared at the layer/substrate interface. This microstructure was related to lead diffusion into the substrate during heat treatment as shown by Rutherford backscattering spectrometry.

We report on the preparation of SiO2 (20%)–TiO2 (80%) planar waveguiding layers by dip-coating technique. The layers are formed from originally prepared sol with the added CdO and the subsequent precipitation of CdS nanocrystals (NC) during H2S treatment. The initial sol doping up to 92 wt.% was reached. The determination of the refractive index and thickness of waveguiding layer by m-line spectroscopy is presented. The porosity of film is evaluated. Influence of carbon contamination of the layer's pre-surface area on the waveguiding properties is discussed. The possibilities of surface relief gratings as efficient input and output light couplers are demonstrated.

We report on the implementation of a two-grating coupler technique for measurement of repopulation of deep traps in CdS nanocrystallites embedded in a (Si 0.2 Ti 0.8 )O 2 waveguiding glass layer of high refractive index. A sol–gel process is used to produce this waveguide. The low attenuation (∼1 dB/cm) of the waveguide allows to in- and out-couple light by surface relief gratings embossed on the top layer of the waveguide. The spectral region of waveguiding (≈700 nm) that was studied corresponds to the deep trap spectral position in CdS. The waveguiding beam is used as a probe beam and we used the third harmonics of a YLF:Nd laser (347 nm) as a pump. The influence of bimolecular recombination on repopulation of deep traps is demonstrated. The linear recombination time as well as bimolecular and Auger coefficients are determined.

In this paper the optical properties of thin films comprising J-aggregated dyes (TDBC) in a polymeric matrix (PVA) deposited on a metallic (silver) layer are studied. Angular reflectometry experiments are conducted in order to obtain the dispersion energy curve of the Surface Plasmon (SP) in relation with the exciton mode. It exhibits an anticrossing behavior characteristic of the strong coupling regime. Simulations using a transfer matrix method with complex optical indices are applied and discussed. They show a roughly good agreement with the experimental results and allow us to estimate the value of the oscillator strength of organic J-aggregate semi conductors used in our experimental studies.

Light induced grating experiments have been performed at room temperature in CdS nanocrystallites of 2.5 nm radius embedded in sol-gel glass films of different semiconductor volume concentration. The dynamics of the photogenerated carriers at the lowest transition peak has been shown to depend on the excitation intensity. No spatial diffusion is observed up to a nanocrystallite volume concentration of 35%. Below a few MW/cm2 the carriers relax in each nanocrystallite, either radiatively in ∼150 ps or by trapping the electrons 15 meV below their excitation transition. For higher intensities of excitation, a saturation of the excited states occurs which allows the electrons to be trapped in the glass matrix, inducing a permanent grating by the creation of a static electric field.

Linear optical properties (absorption and refractive index) of nanocrystalline CdS particles embedded in a silica thin film prepared by a sol-gel technique are presented. Three important parameters of elaboration are particularly pointed out: gelification time, the number of deposited layers and the semiconductor particles volume concentration up to 29%. The values of the refractive index as determined by m-line spectroscopy versus concentration, are analyzed in terms of the Maxwell-Garnett theory.

International audience; Plasmonic Tamm states are interface modes formed at the boundary between a photonic structure and a metallic layer. These modes present both the advantages of surface plasmons and of microcavities photonic modes. Tamm plasmons can be spatially confined by structuring the metallic part of the system, thus reducing the size of the mode and allowing various geometries. They are very good candidates for optimizing the emission properties of semiconductor nanostructures. Recently the extraction of single photons emitted by a quantum box has been evidenced in a Tamm Plasmon structure. Due to the relatively low damping and the versatility of the Tamm geometries, these modes are also good candidates for new type of lasers.

Nanocrystallites of CdS of constant mean radius are embedded in various concentrations (up to 29%) in pure silica glass obtained by a sol-gel technique. Doped glass samples as well as thin glass layers deposited on microscope slides are prepared and structurally characterized by electron microscopy. The linear optical properties (absorption coefficient and index of refraction) of these CdS-doped glasses are measured as functions of the CdS volume fraction in the samples. Their third order nonlinear optical susceptibility is also determined by degenerate four-wave mixing experiments near resonance. The values obtained for samples with different CdS volume fraction are compared to those of bulk CdS platelets.

In this Letter, we show that the strong coupling between a disordered set of molecular emitters and surface plasmons leads to the formation of spatially coherent hybrid states extended on macroscopic distances. Young-type interferometric experiments performed on a system of $J$-aggregated dyes spread on a silver layer evidence the coherent emission from different molecular emitters separated by several microns. The coherence is absent in systems in the weak-coupling regime demonstrating the key role of the hybridization of the molecules with the plasmon.

CdS doped amorphous silica was prepared by the sol-gel method. The CdS concentration in weight varied from 5% to 20%. The samples were characterized by four different and complementary techniques: X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), low frequency inelastic Raman scattering (LOFIRS) and small angle X-ray scattering (SAXS). These observations show that the size of the nanocrystals does not depend on the CdS concentration.

AlMn and AlFe multilayers have been mixed at various temperatures (450, 493 and 77 K) with 800 keV Xe + ions. The mixing stages as a function of dose at various temperatures and the nature of the synthesized phases have been characterized using three complementary techniques: Rutherford backscattering spectrometry (RBS) to observe the spatial distribution resulting from the mixing process at the interfaces; transmission electron microscopy (TEM) observations to determine the microstructures and phases; and conversion electron Mossbauer spectroscopy (CEMS) in the case of AlFe alloys for the study of local order evolutions. Mixing efficiency and nature of the elaborated phases depend on ion dose and temperature of the sample. A dose of about 3 × 10 16 ions/cm 2 is necessary to obtain homogeneous amorphous alloys at 77 K, while the quasicrystalline phases are formed at 450 K (AlMn) or 493 K (AlFe) for a dose of 8 × 10 15 ions/cm 2 . In the AlFe alloys, the local environments of the Fe-atoms deduced from CEMS show different characteristic evolutions for amorphous and quasicrystalline phases with a combination of several sites the relative proportions of which vary at each intermediate mixing stage. Optical (reflectivity) and transport (resistivity, magnetoresistance) measurements performed on the homogeneous mixed films exhibit different electronic structures of the phases and different magnetic behaviors for AlMn (spin glass transition) and AlFe (weak localization).

Al and Fe multilayers thermally evaporated on sapphire substrates have been mixed by irradiation with 800-keV ${\mathrm{Xe}}^{+}$ ions at two different temperatures (liquid-nitrogen temperature and 493 K) and with fluences ranging from 2\ifmmode\times\else\texttimes\fi{}${10}^{15}$ to 3\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ions/${\mathrm{cm}}^{2}$. The structural evolution of the irradiated samples has been followed using complementary characterization techniques such as transmission electron microscopy and conversion-electron M\"ossbauer spectroscopy. Homogeneous amorphous or quasicrystalline phases are obtained at doses of 3\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ions/${\mathrm{cm}}^{2}$ at 77 K or 8\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ions/${\mathrm{cm}}^{2}$ at 493 K, respectively. Different evolutions with ion dose are observed in both cases involving combinations of various sites that tend to final states with dominant local environments characteristic of amorphous or quasicrystalline phases.

The fabrication of microcavities by a sol–gel process and their optical properties are described. The cavities are constituted of an Eu3+-doped SiO2 active layer inserted between two Bragg mirrors, fabricated by stacking alternatiely undoped TiO2 and SiO2 sol–gel thin films. Eu3+ luminescence modification due to the cavity effect, intensity enhancement and modification of the line shape has been observed, and shows a cavity quality factor of 1200. The reflectivity factor of the associated Bragg mirrors reaches 99.8% for seven alternate SiO2/TiO2 layers.

In the framework of optical telecommunication systems, many functions are integrated on the same substrate. Nevertheless, one of the most important, such as isolation, is achieved using discrete components. It is based on magnetic materials which are always difficult to integrate with classical technologies. This is due to the annealing temperature of magnetic materials. In this paper we present another way for the realisation of such components. We use a dip coating process to report a magnetic nanoparticles doped silica layer on ion-exchanged glass waveguide. The advantages of this method is discussed and we demonstrate its compatibility with ion-exchanged technology. By varying the refractive index of the layer, we can adjust the interaction between the waveguide and the magneto-optical layer.

International audience; We study localized surface plasmons in strong coupling with excitons of organic semiconductors. The plasmons are localized in lithographed silver nanodisks organized in square array. A giant Rabi splitting energy of 450 meV is obtained, and typical behaviors of mixed states, i.e., anticrossing of their energies and crossing of their linewidths, are observed. Three-dimensional finite-difference time-domain simulations and coupled oscillator calculations are used to analyze and corroborate the experimental results.

We report on the strong coupling between inorganic quantum well excitons and surface plasmons. For that purpose a corrugated silver film was deposited on the top of a heterostructure consisting of GaAs/GaAlAs quantum wells. The formation of plasmon/heavy-hole exciton/light-hole exciton mixed states is demonstrated with reflectometry experiments. The interaction energies amount to 21 meV for the plasmon/light-hole exciton and 22 meV for the plasmon/heavy-hole exciton. Some particularities of the plasmon-exciton coupling were also discussed and qualitatively related to the plasmon polarization.

The properties of organic semiconductor excitons in strong interaction with surface plasmons are described. For this purpose, a $J$-aggregated cyanine dye layer is deposited on a silver film and studied with reflectometry experiments. The dependence of the Rabi splitting with the square root of the dye layer absorption and the width inversion of the reflectometry lines at the resonance are observed. The experimental spectra are well fitted using a transfer matrix method with a complex index. The comparison between experiments and simulations for layers in different configurations is qualitatively related to the role of the plasmon polarization in the interaction with the aggregated dye chains. Finally, large Rabi splitting of $300\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ are observed for pure dye layers. Characteristic behavior of the large coupling and the effect of asymmetrical absorption line shape are analyzed.

We have developed LiIO3/laponite nanocomposite thin films to form waveguides with quadratic nonlinear optical properties. The films are dip-coated and annealed to induce LiIO3 crystallisation within the laponite matrix. LiIO3 nanocrystal orientation can be controlled using an electric field during the annealing process. In this article we perform the characterisations of the nanocomposite films through m-line spectroscopy and second harmonic generation microscopy (SHGM). Both refractive indexes deduced from m-line spectra and the SHG signal are shown to depend on the nanocrystal orientation distribution, and a relationship between the optical properties and microscopic structure of the films is developed.

We report the fabrication of a carbon nanotube silica composite. This inorganic composite is produced with the sol–gel technique and deposited in thin films by the dip-coating method. The functionalization of multiwall carbon nanotubes is a decisive step in order to introduce them inside a silica matrix. Functionalization ensures good homogeneity of multiwall carbon nanotubes. Atomic force microscopy and surface enhanced Raman spectroscopy demonstrate the well dispersion at the nanometer scale and a micrometer scale, respectively. Moreover, AFM measurements show carbon nanotubes are present in individualized form.

A novel Laponite-lithium iodate nanocomposite has been synthesized for nonlinear optical applications. The elaboration starts with the addition of a lithium iodate aqueous solution to a colloidal suspension of Laponite JS. Thin layers, elaborated using the dip-coating technique, form waveguides and the linear dependence between the lithium iodate concentration and the refractive index and the control over the thickness allow one to optimize waveguiding properties. Waveguides show an attenuation of about 2 dB/cm and easily detectable second harmonic generation. For the nonlinear effective coefficient a value of 1.6 pm/V has been measured. X-ray structural characterization shows that after drying and heat-treatment between 150 and 200°C, lithium iodate crystallizes in the matrix with the crystallite size ranging from 20 to 50 nm. Due to the natural dipole moment of lithium iodate, the orientation of nanocrystals could be controlled using external electric field. The influence of the orientation on the nonlinear optical properties has been determined and compared with the simulations based on a matrix model considering the nanocomposite as a stack of linear and nonlinear 1D layers with fixed or random orientation. A good agreement is achieved between the experiment and the simulation.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The fabrication and the study of sol gel-microcavities strongly doped with CdSe nanocrystals are presented. The Fabry-Perot microcavities are formed by a Distributed Bragg Reflector covered with a CdSe doped active layer and a silver mirror. These microcavities are studied with reflectometry experiments. We observe that the cavity resonance peak is enlarged by a factor two when his spectral position corresponds to the first absorption line of the CdSe nanocrystals. Transfer matrix method calculation taking into account the CdSe absorption have been performed and are in good agreement with the experimental values.

We report on the observation of a strong coupling between a surface plasmon and an exciton. Reflectometry experiments are performed on an organic semiconductor, namely, cyanide dye J aggregates, deposited on a silver film. The dispersion lines present an anticrossing that is the signature of a strong plasmon-exciton coupling. Mixed states are formed in a similar way as microcavities polaritons. The Rabi splitting characteristic of this coupling reaches 180 meV at room temperature. The emission of the low energy plasmon-exciton mixed state has been observed and is largely shifted from the uncoupled emission.

The fabrication and the studies of sol gel-microcavities strongly doped with CdSe nanocristals are presented. The Fabry-Perot microcavities are fabricated by a Distributed Bragg Reflectors which is covered with an active layer and a silver mirror. The matrix of the doped layer is the ZrO 2 material. These microcavities are characterized by reflectometry. The resonant peak is enlarged when his spectral position corresponds to their first absorption line. This means a strong interaction between the narrow peak of the cavity mode and the large first absorption line of the nanocrystals.

In recent years, a large amount of activity has been carried out searching new materials for second order non-linear optics. Nanostructured materials composed of a host matrix and optical active nanocrystals form a new part of this research field. Our present work consists in "doping" SiO 2 matrices with 5 to 30% mass of LiIO 3 nanocrystals. Indeed, α-LiIO 3 is a compound known to be very efficient for second harmonic generation (SHG). This nanocomposite glass has been developped using sol-gel technics. Bulk samples have been first studied showing nanocrystallites with size ranging from 50 nm to 400 nm and second harmonic generation (SHG). Then thin layers have been elaborated using dip coating and spin coating technics. Being given that LiIO 3 crystals present structurally a strong dipolar moment, non-linear optical properties could be enhanced using Corona discharges to orientate nanocrystals. This paper relates the fabrication process and the structural and optical characterizations of bulk and thin layer material.

The fabrication and the optical properties of sol-gel high quality DBRs and microcavities are described and the emission of the europium ions included in the cavity observed. The microcavities are constituted of an SiO2 half wave Eu3+ doped active layer inserted between two sol-gel Bragg reflectors. These reflectors are formed by a stack of alternated quarter wave films of SiO2 and TiO2. Films were deposited by a dip coating method. To fabricate high quality Bragg mirrors, a large number of layers has to be stacked, but sol gel thin layers develop internal stresses during the drying and firing processes, leading to defects and cracks into the stacked films. The study of the stresses in the layers shows that a short 900°C layer annealing solves this problem and the number of stacked layers can be greater than 60 without cracks. A microcavity with 7 doublets Bragg mirrors has been fabricated using this process. Eu3+ luminescence modification due to the cavity effect, intensity enhancement and modification of the lineshape, has been observed, showing a cavity quality factor of 1200. The reflectivity factor of the associated Bragg mirrors reaches 99.8% for seven alternated SiO2/TiO2 layers.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Structural and optical studies on erbium-doped nanomaterials are of broad interest due to their large potential in advanced photonic applications [1–8]. Their wet chemical processing (sol-gel, solution combustion synthesis, colloidal routes etc.) has been largely explored using different erbium hosts such as titania [1], zirconia [2], II-VI-semiconductors [3,4], aluminosilicates [5], silica [6,7] as well as yttria [8]. Of particular interest to us are the ErIII- doped planar wave guides prepared from so-called ”polymeric sols” containing weakly branched molecular clusters. Previous optogeometrical studies [1, 2] on these sol-gel nanostructures have indicated that thermal annealing of wet gel layers seems to be the most crucial processing step. Critically: 1. elimination of high energy vibrations (liberating organics and OH-groups), 2. blocking of Er-clustering as the result of phase separation/transformation processes 3. suppression of nanocrystal formation/growth which give rise to increased scattering are needed in order to achieve the optimal active waveguide performance (reduced damping losses and a long life time of the photoexcited ErIII ions).

We report here the successful inclusion of carbon nanotubes (CNs) into a TiO2 matrix prepared by a sol–gel method. The presence of CNs in the sol–gel matrix and the structure of the film were analyzed principally by transmission electron microscopy. Complementary information about the behavior of embedded carbon nanotubes versus heat treatment and ion irradiation were obtained by X-ray photoelectron spectroscopy. The elaboration of an inorganic matrix containing embedded carbon nanotubes leads to a new nanocomposite. The possible applications of this nanocomposite are discussed.

We present experimental results of a Kretschmann-prism coupler method used in Raman scattering experiments with ultrathin (few nanometers) TiO2 sol–gel films deposited on a metallic silver layer characterized by surface plasmon resonance (SPR) experiments. In this article, we describe a new optical device as an application of SPR properties and coupled with a micro-Raman scattering setup. The enhancement factor (150) of the Raman intensity in comparison to the classical way allows us to determine the critical thin films structure. Optical results are then discussed and compared to transmission electron microscopy.

Very thin TiO2 films have been prepared by sol–gel and deposited on a silver layer for Surface Plasmon Resonance (SPR) measurements. Densification of the samples has been studied by determining from SPR measurements the optical index (ranging from 1.68 to 1.92) and thickness (ranging from 6 to 2 nm) at each step of the annealing procedure. The structure of the layer (amorphous and/or crystalline) has been checked at the final stage of the thermal treatment by High Resolution Transmission Electron Microscopy (HRTEM).

The different steps of thin film preparation by a sol-gel process are discussed: preparation of the starting solutions, control of the viscosity of the sol, deposition methods and thermal treatments. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Waveguide Raman Spectroscopy (WRS) are used to obtain structural characterization of the layers. The option of matrix doping is cited. Some optical properties of thin films using waveguide techniques and non-linear properties are underlined.

A Laponite clay-based lithium iodate nanocomposite have been synthesized for nonlinear optical applications. After addition of lithium iodate aqueous solution to a colloidal suspension of Laponite JS, thin layers are elaborated from this sol using dip-coating technique. After drying and heat treatments between 150 and 220°C, LiIO3 crystallizes in the matrix with nanometer size. As a result of their strong dipolar moment, the LiIO3 crystals can be orientated under an external electric field during nucleation. Planar waveguides have been elaborated on glass substrates and studied using m-lines spectroscopy. The experimental nonlinear optical response has been compared to predictions of a model and an effective nonlinear coefficient deff=1.4pm∕V has been measured.