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We demonstrate 1.7–18 µm mid-infrared coherent supercontinuum generation by means of the full transmission window of a unique dispersion-engineered step-index Ge-Se-Te fiber. Our study thus opens the entire molecular fingerprint region to future chalcogenide fiber platforms.

In this paper, the impact of the post-heat-treatment on the structural and spectroscopic properties as well as on the chemical durability of a thermally stable Er3+-doped phosphate glass in the system P2O5 - K2O - Al2O3 - B2O3 - BaO - PbO - La2O3 - Gd2O3 is reported. Two crystalline phases, namely La, Gd-monazite and AlKP2O7, were found to precipitate from the surface of the glass after heat-treatment, as confirmed by both X-ray Diffraction (XRD) and Scanning Electron Microscopy/Energy Dispersive X-ray (SEM/EDX) analyses. Moreover, the heat-treatment was responsible for the formation of a more polymerized glass network close to the surface crystalline layer as evidenced using micro-Raman spectroscopy. From the changes in the Er3+ optical properties, some of the Er3+ ions are suspected to enter in the crystals. Both the as-prepared and heat-treated glasses were subjected to a degradation test in hydrochloric acid (HCl) and showed a congruent and incongruent dissolution behavior, respectively.

International audience

International audience; The development and the emergence of fully integrated all-fiber optical systems is very interesting from a technical point of view in photonics. Indeed, the development of mutimaterials fibers combining both optical waveguide properties and simultaneous in-fiber electrical excitation could provide plenty of innovative signal-processing, sensing or imaging functionalities. Here, we report the engineering of a new glass/metal composite fiber. For the glass, we have chosen tellurite glasses for their excellent thermo-viscous abilities (low Tg) and linear/nonlinear optical properties. This low Tg allows to have a larger panel of potential metals to be co-drawn with. The synthesis is firstly realized by build-in-casting at room atmosphere which allows to get a large-core. Then, the rod-in-tube technique and the insertion of metallic wires allow to get a step-index fiber with a small-core (7µm) and two continuous metallic electrodes running along the fiber axis (Øelectrodes = 30µm). Thus, we obtain a tellurite-based core-clad dual-electrode composite fiber made by direct, homothetic preform-to-fiber thermal co-drawing. The rheological and optical properties of the selected glasses allow both to regulate the metallic melting flow and to manage the refractive index core/clad waveguide profile. We will discuss the engineering of these multimaterials optical fibers and their characterization: thermal and viscosity properties, linear optical properties (loss), electrical properties with a continuity of the electrodes over meters of fiber.

Optical fibers mid-infrared (mid-IR) supercontinuum (SC) generation for sources covering the 1–20 μm range are of great interest for many applications in optics, spectroscopy, sensing for environmental monitoring or medical diagnosis and treatment. We present here our work regarding two low phonon energy glasses families, leading to highly nonlinear optical fibers for SC generation: tellurites and seleno-telluride glasses. Tellurite fibers are suitable for working in the 1-5 μm range, when seleno-telluride ones are intended to the 2-16 μm range. For tellurites, we focus on the definition of glass pairs suitable for the drawing of step index fibers with a controlled chromatic dispersion for a femto-second (fs) pumping around 2 μm. In the case of chalcogenide glasses, we focus on the Ge-Se-Te ternary system, which offers the advantage of allowing the drawing of step index or micro-structured fibers avoiding the usage of toxic arsenic. Depending on the fiber geometry the management of the chromatic dispersion is quite different. Suspended core fibers allow to shift deeply the unique zero dispersion wavelength (ZDW) towards short wavelengths for fs pumping around 2- 3 μm. For step index fibers, it is possible to design waveguides with no, one or two ZDW. Various pumping schemes are available between 3 and 9 μm, with a fs tunable source. As a result, SC generation experiments in these different fibers allows to reach wide spanning spectra, between 1 and more than 5 μm for tellurite fibers, and between 2 and more than 14 μm in the case of chalcogenides ones.

Here, we propose to design a new class of glass/metal composite fibers for all-guided optical-electrical signals. The objective is to combine metal and glass materials by using additive manufacturing approach to engineer multimaterials fibers. Thus, after manual insertion of metallic electrodes into the tellurite glass preform, we can obtain the first tellurite-based core-clad dualelectrode composite fiber made by direct, homothetic preform-to-fiber thermal co-drawing.

Mid-infrared supercontinuum generation from 1.5 to 4.5 &micro, m with sub-nanojoule femtosecond pump pulses is demonstrated by using a short segment of dispersion-engineered step-index tellurite fiber with very low OH content. Distinct group-velocity dispersion regimes in a simple design of step-index tellurite fiber are also reported, which allows to choose the nonlinear pulse propagation regime according to the required tailoring of the supercontinuum source. Numerical simulations based on the generalized nonlinear Schr&ouml, dinger equation are used to determine optimized fiber parameters before experimental demonstrations. We also analyse the coherence properties of the resulting supercontinuum sources.

Development of broadband supercontinuum sources has been studied since decades for its high application potential in various fields like spectroscopy, medical science and others. First experiments were made with silica but the results shown the need to find new materials for supercontinuum generation in the IR wavelength range. Two types of materials have been found interesting for supercontinuum generation: chalcogenide and tellurite glasses. These materials have a high non-linear refractive index and a good transmission in infrared which provides a high potential for applications. Bulks tellurite glasses transmit until 5µm while bulks chalcogenide glasses transmit until 12-20µm depending on their composition. We report here the synthesis of low-OH step-index tellurite fibers and their linear and non-linear characterization. The synthesis is firstly realized by build-in-casting in a glovebox which allows to get a large-core preform(∅clad/∅core  2) and a large core corresponding fiber(∅core  60µm). Then, the rod-in-tube technique allows, from the jacketing of the stretched initial preform, to get a small-core preform and subsequently a small core fiber (∅core  3.5µm). The minimum of losses of the large-core fiber is below 1dB/m, the IR transmission wavelength exceeds 4 µm on several meters of fibers and reaches more than 5 µm on small samples (several centimeters long). We have developed core-clad composition with a large refractive index difference (∆n=0.132) which provides a high confinement in our step-index fibers. We discuss the supercontinuum generation in these fibers exploiting numerical simulations based on the generalized nonlinear Schrodinger equation and then we present the supercontinuum experimental results obtained between 1 and 5µm. Most of pollutant and greenhouse gases emitted by human activity, including methane, carbon dioxide and nitrous oxide, absorbs in the mid-IR. The spectroscopic experiments realized on the gases through supercontinuum generation between 1 and 5 µm are presented.

We present the experimental development of dispersion-engineered tellurite fibers based on a simple step-index profile for mid-infrared supercontinuum generation. A supercontinuum spanning from 1.5 to 4.5 μm is obtained in a 12-cm-long fiber.

We present an overview of the fabrication process and characterization of germanate, germanate-tellurite and tellurite microstructured fibers or step-index fibers with different index contrasts. For microstructured fibers, we exploit the generated SC for methane spectroscopy measurements in the mid-infrared by means of the supercontinuum absorption spectroscopy technique. We demonstrate also an ageing process of microstructured fibers in ambient atmosphere. For stepindex fibers, several compatible core/cladding glasses were explored for fiber manufacturing with a dehydration process, allowing the drawing of low-OH tellurite fibers. We report both numerical and experimental demonstrations supercontinuum (SC) generation in these fibers. Finally we report our latest results in the generation of SC until 5.3 μm in a step-index tellurite fiber.

International audience

International audience; We demonstrate the fabrication of arsenic-and antimony-free chalcogenide glasses compatible with glass fiber processing. Optical fibers with distinct index profiles are presented and characterized, namely, single-material fibers with or without a suspended core and standard step-index fibers with varying core diameter. In addition, we evidence their potential for nonlinear photonic devices in the mid-infrared spectral region by means of super-continuum generation experiments in the femtosecond regime. Spectral broadenings extend on several octaves in the mid-infrared from 2 to 14 μm.

The receptor tyrosine kinase Met and its high-affinity ligand, the hepatocyte growth factor/scatter factor (HGF/SF), are essential to embryonic development. Deregulation of their signaling is associated with tumorigenesis and metastasis, notably through receptor overexpression. It is thus important to understand the mechanisms controlling Met expression. The ligand-dependent internalization of Met and its subsequent degradation in the lysosomal compartment are well described. This process is known to attenuate downstream Met signaling pathways. Yet internalized Met takes part directly in intracellular signaling by chaperoning signaling factors in the course of its trafficking. Furthermore, recent studies describe various new degradation mechanisms of membrane-anchored Met, involving proteolytic cleavages or association with novel partners. Although all these degradations are ligand-independent, they share, to different extents, some common features with canonical HGF/SF-dependent degradation. Interestingly, activated Met variants display resistance to degradation, suggesting defective degradation is involved in tumorigenesis. Conversely, forced degradation of Met through reinduction of one or more degradation pathways is a promising therapeutic strategy.

We present an overview of the fabrication process and characterization of tellurite, germanate, and germanate–tellurite step-index fibers with different index contrasts. Several compatible core/cladding glass pairs were first explored for fiber manufacturing under ambient atmosphere. The potential of the resulting waveguides for nonlinear optics is revealed by means of supercontinuum generation experiments using a near-infrared femtosecond fiber laser. Fabrication of the glass preforms was also adapted to dehydration procedures, allowing the drawing of low-OH step-index tellurite fibers. The beneficial impact of glass purification on supercontinuum generation toward the mid-infrared region is confirmed.