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International audience; We report recent results obtained with a novel optical fiber experimental setup based on a heterodyne optical time-domain reflectometer in the context of FPU recurrence process. Moreover, we actively compensate the dissipation of the system. We show that we can observe several FPU recurrences by monitoring the power and relative phase evolutions of the main discrete frequency components involved in the process.

International audience; We investigate theoretically and experimentally the modulation instability process in a dispersion oscillating fiber characterized by an amplitude modulation of its group velocity dispersion. We developed an analytical model that allows us to calculate the parametric gain in these fibers and to predict the position of the quasi-phase matched modulation instability sidelobes. The two fundamental frequencies characterizing the dispersion profile lead to the splitting of the original multiple sidelobes generated in basic sinusoidally varying dispersion oscillating fibers. These theoretical predictions are confirmed by experiments.

This work presents a laser desorption study of Ga 5 Ge 20 Sb 10 S 65 chalcogenide glasses. The desorption products have been analyzed by UV multi-photon ionization and time-of-flight mass spectrometry. Desorption mechanisms and plume dynamics have been investigated by studying the desorption products velocity distribution profiles in the frame of a Knudsen layer model. A peculiar behavior (broadening of the mass spectral lines) of the Ga component was found at high desorption–ionization delays and a tentative explanation has been proposed, based on the very different thermal properties of the sample constituents.

International audience; An innovative way is proposed here to synthesize chalcogenide glass-​CdS nanocrystal composites by hot-​pressing a combination of Ge20Sb12S68 glassy powder and nonlinear CdS nanoparticles. The cadmium sulfide nanoparticles, which possess the second-​harmonic generation property, were synthesized from basic cadmium soln. strongly complexed by amine. The obtained nanocomposites present a homogeneous distribution of the crystals. The transmission reaches 30​% at 5 μm and up to 60​% at 10.6 μm. The second-​harmonic generation at 0.9 μm has been detected. This technique can overcome the uncontrollable hetero-​crystn. which tends to occur in the glass-​ceramics prepd. by the conventional thermal treatment method.

Spatial Maker fringe experiments have allowed us to render evident large differences in the shape of the second-order χ (2) susceptibility, induced by thermal poling, in Infrasil and Suprasil silica plates. To determine more accurately the spatial repartition of the induced χ (2) , two methods were used. The first one consists of increasing the pump beam internal angle span by placing a pair of hemispherical lenses against both sides of the poled plates. The second consists of polishing the plates and then measuring the second harmonic power generated within the samples. We explain all the experimental observations by the existence of a bulk χ (2) within the whole volume of Suprasil poled glass.

Poling has been achieved in a specially designed germanosilicate fiber. The Ξ(2) susceptibility was detected and measured through refractive index changes measurements using an interferometric method within the fiber. Two methods for poling have been used: the thermally-assisted electrical method and the UV-assisted electrical method. Both the poling techniques and the results concerning the linear electro-optic effect are presented.

We herein report the comparison of two independent reconstructions of the distribution of the /spl chi//sup (2)/ nonlinear susceptibility induced by thermal poling in planar silica samples. Both nonlinear profiles are quantitatively in good agreement in terms of /spl chi//sup (2)/ magnitude and nonlinear thickness; and qualitatively in agreement in terms of shape. We conclude that both characterization methods used are efficient for the determination of the /spl chi//sup (2)/ susceptibility spatial distribution in bulk samples.

Permanent photoinduced high index changes are reported for the first time to our knowledge in terbium doped alumino-silicate optical fibres exposed to pulsed UV laser light. The fibres were made photosensitive using the room temperature high pressure hydrogen loading technique. The dependence of photosensitivity on both terbium concentration and pump wavelength has been established. Both UV and visible absorption changes were investigated when fibres were exposed to pulsed UV laser irradiation. The net changes in the spectra failed to account for the observed UV induced refractive index changes according to Kramers-Kronig relationship. Preliminary results on the thermal behaviour of the gratings are also reported.

International audience; This work provides a new approach for preparing chalcogenide glasses and glass-ceramics. A process combining the mechanical milling and the spark plasma sintering was developed to synthesize non-linear chalcogenide glass-ceramic. GeS2 glass-ceramics containing β-GeS2 crystals homogenously dispersed within the glassy matrix were manufactured. Their transmission reaches 30% in the infrared region. This new method overcomes the limitation of the traditional way for preparing GeS2 glass-ceramics where an uncontrollable crystallization leads to the glass opacity. The non-centro-symmetric β-GeS2 phase makes the GeS2/β-GeS2 glass-ceramic a very promising material for the generation of permanent second order non-linear phenomenon.

We investigate the role played by fourth-order dispersion on the modulation instability process in dispersion oscillating fibers. It not only leads to the appearance of instability sidebands in the normal dispersion regime (as in uniform fibers), but also to a new class of large detuned instability peaks that we ascribe to the variation of dispersion. All these theoretical predictions are experimentally confirmed.

We report the experimental demonstration of the modulation instability process in optical fibers with a periodic longitudinal evolution of dispersion. The process is characterized by the spontaneous growth of multiple sidebands through quasi-phase-matching.

The evolution of the second-harmonic signal is monitored as the poled sample is etched with hydrofluoric acid. The sample thickness is measured in real time using an interferometric method. The full set of data allows us to fully reconstruct the nonlinear spatial distribution created inside the glass, whatever the nonlinearities’ origin.

Thin layers of silica have been removed from thermally poled samples using a hydrofluoric acid etching. After each etching, the second-harmonic signal generated within the remaining glass has been recorded by means of a Maker fringes experiment. Evidence of a sign reversal within the nonlinear distribution is pointed out for 10-min poled Infrasil™ samples.

We investigate experimentally the MI process in a dispersion oscillating fiber. An important number of unstable frequencies over 10 THz are generated that then lead to a new degree of freedom for tailoring nonlinear effects.

A simple analytical model is developed to analyze and explain the complex dynamics of the multi-peak modulation instability spectrum observed in dispersion oscillating optical fibers [M. Droques et al., 37, 4832-4834 Opt. Lett., (2012)]. We provide a simple expression for the local parametric gain which shows that each of the multiple spectral components grows thanks to a quasi-phase-matching mechanism due to the periodicity of the waveguide parameters, in good agreement with numerical simulations and experiments. This simplified model is also successfully used to tailor the multi-peak modulation instability spectrum shape. These theoretical predictions are confirmed by experiments., Comment: 18 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1207.4667

Temporal beats between two separate pulsed lasers of different adjustable frequency are used as a means of measuring the temporal transfer function of a single-shot picosecond streak camera. We describe two parallel pulse generators that use tunable distributed-feedback dye lasers. These lasers produce two pulses of different frequency that interfere at the camera. The temporal fringe contrast at the camera output provides a direct measure of its transfer function. Fringe spacing combined with spectroscopic measure of the laser wavelengths provides a calibration of the temporal scale.

We report the experimental demonstration of "discrete focusing" inside a 60-cm-long optical fiber made of a 2D square array of coupled waveguides. The suitable input amplitude and phase distributions are imposed by using a spatial light modulator. Thus we demonstrate that focusing in a single core at the output by discrete propagation is possible despite some amount of transverse heterogeneities of the waveguide array.

The spatial distribution of the second-order nonlinearity induced in thermally poled Infrasil silica samples is recorded after thermal annealing experiments. Two regimes have been studied: short and long poling durations. For short poling durations, the observations are in good agreement with a model where only one ion type recombines inside the depletion region. The nonlinear distribution and erasure observed for the other case are well explained by considering the addition of another positive-charged ion injected during the poling process. This second ion acts as a barrier during thermal annealing and reduces the mobility of the first one.

International audience; High second-order susceptibility has been created in a chalcogenide glass from Ge-Sb-S system. A thermal poling process was used to produce this non-linear effect and a second harmonic generation experiment allowed characterizing the phenomenon. A maximum χ(2) value of 8.0±0.5 pm/V was measured for the first time to our best knowledge in sulfide glasses.

Second harmonic generation (SHG) has been obtained in a sample of Ga5Ge20Sb10S65 glass submitted to a thermal poling treatment. An original characterization method is used for the determination of the induced second-order nonlinear profile. A reproducible chi(2) susceptibility of 4.4 +/- 0.4 pm/Volt was achieved for specific poling conditions.

Optical fibers are interesting tools for early diagnostic of various diseases through micro-endoscopy. For this purpose laser scanning imaging with a multicore image guide can be used [1-3]. Easy reconstruction of the image and interfacing with semiconductor detection would however require the cores to be arranged in a square lattice while maintaining the polarization state of the input light.

International audience; New class of chalcohalide glasses has been prepared in the GeS2-In2S3-CsI system with regard to their potential non-linear properties. The study of glass-forming region was undertaken to select glassy compositions, which present high non-linear (NL) optical properties with a low two-photon absorption. Thermal analyses, structural examination by Raman spectroscopy, non-linear optical measurements were investigated as a function of CsI contents. Introduction of CsI has shifted the band-gap edge towards the blue region of the absorption optical spectrum and therefore has limited the two-photon absorption. Their NL refractive index n2 are 60 times higher than silica glasses without any NL absorption. Moreover, second harmonic signal was observed in thermally poled samples similar to silica glass. However, this second order non-linearity is not temporally stable.

Due to their intrinsic nature, chalcogenide glasses present attractive nonlinearities from third and second order, with values reaching between 10 and 1000 times those of silica. We present a study of their properties and their shaping with the purpose to reach efficient devices in the near-mid infrared.

International audience; High second-order susceptibilities are created by thermal poling in bulk germanium disulfide based chalcogenide glasses. Experimental conditions of the poling treatment (temperature, voltage, time) were optimized for each glass composition. The second-order nonlinear signals were recorded by using the Maker fringes experiment and a second-order coefficient χ(2) up to 8 pm V-1 was measured in the Ge25Sb10S65 glass. This value is obtained using a simulation based on accurate knowledge of the thickness of the nonlinear layer. Two mechanisms are proposed to explain the creation of a nonlinear layer under the anode: the formation and the migration of charged defects towards the anode may mainly occur in Ge20Ga5Sb10S65 and Ge25Ga5S70 glasses, whereas the migration of Na+ ions towards the cathode may be responsible for the accumulation of negative charges under the anode in Ge33S67 and Ge25Sb10S65 glasses. Different electronic conductivity behaviors seem to be at the origin of the phenomenon. In parallel, the potential effect of the poling treatment on the structural and electronic properties is studied using Raman spectroscopy and secondary ion mass spectroscopy measurements.

Silica glass plates (Infrasil from Heraeus) have been thermally poled with different types of electrodes (evaporated or pressed-on) having different chemical compositions (Au, Al, n-doped Si or p-doped Si). We show for the first time to our best knowledge that the profile of the induced second-order nonlinearity strongly depends on the composition of electrodes used for the thermal poling process.

International audience; Permanent second-harmonic generation (SHG) has been demonstrated in chalcogenide based glass-ceramics containing non-linear micro-crystals with a size of a few micrometers. A glass composition from the Ge-Sb-S system was chosen as the reference glass for its stability against crystallization and atmospheric corrosion. Metallic cadmium was introduced in this matrix to promote crystallite formation resulting in infrared transparent glass-ceramics. A volume crystallization of β-GeS2 phase was obtained within the glass media by heating the glass samples at 370 °C for different durations. The glass-ceramics were then investigated by Raman spectroscopy, X-ray diffraction and NanoSIMS. The second-order non-linear signals were recorded by using Maker fringes experiment and were studied as a function of the crystallized volume fraction. The results indicated a non-linearity in chalcogenide glass-ceramics about one hundred times lower than α-quartz for a 1 mm thick sample heat treated 144 h.

We present the first observation by transmission electron microscopy of glass densification induced by Bragg grating inscription in two germanosilicate single-mode optical fibers.

Second harmonic generation was obtained with an interesting efficiency in thermally poled sulfide glass. The best results obtained to date for chalcogenide glasses were on a Ge-Sb-S system thanks to an adapted treatment of thermal poling. The poling parameters like temperature (100-310 °C). applied voltage (2.5-4 kV) and duration (5-60min) were explored. A large NL second-order susceptibility X (2) of about 10 ± 0.5 pm/V was measured. The nonlinear susceptibility profile as a function of the depth under the anode for Ge 25 Sb 10 S 65 poled glass was determined using the analyze of remained second harmonic signal during the NaOH etching treatment. In parallel. a study of the concentration variation of elements being able to be involved in the formation of a charge space was achieved by using the secondary ion mass spectroscopy.

We present experimental results of thermal polings performed on Suprasil I samples (Heraeus) under square alternative voltages at various frequencies. We report a large increase (×5 compared to a continuous voltage poling) of the second order non-linear coefficient within a sample poled at 1mHz.

Four characterization techniques are compared in the measurement of the depletion region of silica poled during different time intervals. The effect of pre-etching the samples prior to poling is also investigated.

New opportunities for photonic components result from the discovering of the second harmonic generation (SHG) in thermally poled glasses in the earliest 1990s. It has attracted a lot of interest because it offers new developments in the optical glassy material research. In this context a new tellurite glass with 70%TeO2–25%Pb(PO3)2–5%Sb2O3 composition has been developed and characterized. The structure of the unpoled glass has been studied by IR, Raman, and XAFS spectroscopy. Optical properties of transmission like the linear refractive index and third-order non-linear optical susceptibility χ(3) as well as dielectric susceptibilities have also been investigated. A second harmonic signal was observed for the poled glass which is an order of magnitude better than the silica glass efficiency.

We study numerically the dynamics of the induced second-order nonlinearity in Infrasil® silica glass, with a two charge carrier model. An optimum in poling time is found. Its position depends on the sample thickness.

Thermally poled samples were submitted to a hydrofluoric acid etching. Both the second harmonic signal and the sample thickness were simultaneously recorded. The nonlinear spatial distribution was deduced with a sub-micron resolution

We will describe the European project Glamorous, which involves several research groups working in the field of poling of glass. Objectives and recent results on materials, devices and applications will be reviewed.

Chalcogenide glasses in the [Ge-Se-S-As] system have been synthesized and studied with respect to their nonlinear optical properties from third and second order. Z-scan and Mach Zehnder interferometry measurements of the nonlinear refractive index (n2) and nonlinear absorption ((beta) ) have been performed at 1064 nm. Some z-scan measurements have been also realized at 1430 nm. The results have been correlated to the structures of the glasses and the figure of merit has been calculated with the purpose of a potential utilization of these glasses in the realization of ultra- fast all-optical switches. Nonlinearities as high as 850 times the nonlinearity of silica glass have been obtained and some glasses exhibit at 1430 nm nonlinear optical characteristics suitable for telecommunication applications. The all-optical poling of a chalcohalogenide glass has been realized with a Q-switch mode-locked Nd:YAG laser at 1064 nm emitting 45 ps pulses at a repetition rate of 10 Hz with frequency doubling at 532 nm. A nonlinear coefficient deff equals 2.8 10-17 m/V similar to that of the reference glass Schott SF 57 has been obtained. The thermal poling of a chalcogenide glass also has been realized and a transient second order nonlinear susceptibility (chi) (2) has been observed.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The particular spatial distribution of the second-order nonlinear susceptibility we have observed in poled Suprasil glass samples is experimentally studied as a function of the sample thickness.

This paper describes a new method of chirped fibre Bragg grating fabrication for chromatic dispersion compensation. The technique consists in a constant pitch Bragg grating inscription within an accurately controlled slope of tapered fibre. Chromatic dispersion compensators manufactured are tested in a 10 Gbit/s system experiment. An error free transmission link of 150 km length has been performed.

In this paper we propose a new type of fibre laser configuration which consists of closing an erbium-doped fibre laser cavity by two Bragg gratings (similarly to DBR laser). One of the grating has a Π/2 phase shift at the centre. In the case of passive fibre long Bragg grating with a Π/2 phase shift has narrow transmission peak in the centre of the reflection spectrum. In an active fibre, the spontaneous emission spectrum below threshold exhibits a maximum at the place of the peak in the centre of the reflection spectrum. That would give possibilities to obtain single-frequency oscillation with high output power provided by the long length of the laser cavity.

Far-field properties of the optical power scattered from type IIA gratings photowritten within high NA germanosilicate fibers have been studied under various experimental conditions. First, the evolution of the out- coupling efficiency has been recorded in the course of the grating inscription. This revealed that the scattered power from fiber Bragg gratings sharply increased at the time of arrival of the type IIA photosensitivity. More, the out- coupling efficiency and the reflectivity of the type IIA grating seem to have a similar behavior under a thermal annealing process of the grating. It is then shown that the optical power detected in the far-field is scattered around a cone centered on the fiber axis, with a non-induced azimuthal distribution. The features of the observed pattern can be explained only if the UV induced index change, at the origin of he increase in the scattering efficiency, is non uniformly distributed in a plane perpendicular to the fiber axis.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report the experimental demonstration of a modulation instability (MI) process assisted by a periodic dispersion modulation in an optical fiber. We observe the spontaneous growth of more than 10 pairs of MI sidebands spanning over more than 10 THz thanks to a quasi-phase-matched process.

Experimental works have shown it is possible to realize photo-written cavity lasers with rare earth doped silicate fibres. Most of these new laser sources can be pumped by market laser diodes, what makes them valuables for their integretion in system. Furthermore, their laser effect threshold (1-2 mW), their spectral width (a few Ghz), their conversion rate, close to the theorical value and their wavelength tunablelity allow their use in a wide range of applications such as telecommunications, sensors, etc ... We present here experimental results on a particular application of this kind of lasers in the field of detection of a gas by identification of one of its absorption lines by use of classical linear spectroscopic methods. We have carried out our experiments on an absorption line of water. We present first the making process of the fibre lasers and the method used to insure their tunablelity around the selected absorption line of water. Two lasers have been designed for this work. We give their respective characteristics, i.e. their spectral width, slope, polarisation state and we compare them with the theorical values. Secondly, we give the absorption spectra obtained with both these lasers scanning their wavelength. These spectra consist on the detected light intensity versus the laser wavelength with the laser beam freely propagating through a few meters of absorbing medium. At least, we present the preliminary experimental results on the optoacoustics detection of an absorption line of water obtained using the fibre laser having the best characteristics. The obtained curve gives the detected acoustic power versus scanned wavelength range using a non optimized acoustic cell of a few cm long containing air at room pressure and temperature.

A silicon film sandwiched between a sapphire substrate and a silver layer is used as a nonlinear optical waveguide. The geometrical characteristics of the film and grating coupler have been optimized. This device has been studied in the nonlinear regime using nanosecond and picosecond exciting pulses. Very fast switchings are obtained which can be explained theoretically.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

International audience; A second-order susceptibility χ(2) is created by the thermal poling method in a bulk sample of Ga5Ge20Sb10S65 sulfide chalcogenide glass. We present experimental results focusing on the time-evolution properties of the created nonlinear layer. By cycling the poling operation on a sample, the generated second harmonic signal is improved, and the second-order nonlinearity is shown to be stable over several months. The χ(2) susceptibility profile is carefully reconstructed and its maximum value reaches 4-5 pm/V.

We study the thermal stability of the second-harmonic signal in electron-beam poled silica based thin films developed for this application. Effects of N or Ge concentration as dopant, on one hand, and hydroxyl species, on the other hand, are tested. We conclude that water molecules inducing an ionic conductivity are detrimental to the e-beam poling efficiency and have to be avoided. Nevertheless, despite such precaution, the stability of the second-harmonic signal in an e-beam poled sample is worse than in a thermally poled sample.

The dynamics of the second-order nonlinearity induced in a thermally poled Infrasil silica glass is experimentally and theoretically studied. 200 mum and 500 mum-thick samples have been poled for different durations varying from 1 minute to 100 minutes. After the poling process, the magnitude and the spatial distribution of the induced chi((2)) susceptibility have been characterized accurately with the "layer peeling" method. A two-charge carrier model with an electric field dependant charge injection is used to explain the experimental time-evolution of the chi((2)) profiles. A good agreement between experimental results and simulations is reported.

Both the second-order nonlinear distribution and the built-in electric field have been measured in poled Infrasil™ silica samples, leading to the determination of the third-order nonlinear susceptibility spatial distribution. A difference between the χ(2) and electric field profiles has been observed in the first micrometers near the surface in contact with the anode. This behavior could be attributed to a modification of the χ(3) susceptibility in the poled region.

The second-order nonlinear profile induced within thermally poled Infrasil silica samples is characterized as a function of the duration of the poling process. For poling durations shorter than 5 min the spatial distribution of the chi(2) susceptibility exhibits a triangular shape. This observation, as well as the maximum value of the electric field recorded during poling (1.9 x 10(9) V/m), is in excellent agreement with charge migration models that involve a single charge carrier. It is shown that for higher poling durations the nonlinear profiles tend to flatten; in that case the charge injection mechanisms cannot be neglected. For another point of view, the experimental method introduced herein has allowed us to determine the mobility of the rapid charge carrier involved in the poling process: micro = 1.5 x 10(-15) m2 V(-1) s(-1) at 250 degrees C.

The second-harmonic signal generated within poled silica disks is monitored in real time as the sample is etched with hydrofluoric acid. An oscillating signal is observed when the cathodic side of the sample is etched. This result is in good agreement with the condition of zero potential difference between the two surfaces of the disk. As a result, a negative nonlinear coefficient is induced outside the alkali ion depleted layer.