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Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the mid-infrared spectral range we have developed a biosensor that can collect information on whole metabolism alterations, rapidly and in situ. Thanks to this sensor it is possible to collect infrared spectra by remote spectroscopy, by simple contact with the sample. In this way, we tried to determine spectral modifications due, on the one hand, to cerebral metabolism alterations caused by a transient focal ischemia in the rat brain and, in the other hand, starvation in the mouse liver. We also applied a microdialysis method, a well known technique for in vivo brain metabolism studies, as reference. In the field of integrated microsensors, reactive ion etching was used to pattern rib waveguides between 2 and 300 μm wide. This technique was used to fabricate Y optical junctions for optical interconnections on chalcogenide amorphous films, which can potentially increase the sensitivity and stability of an optical micro-sensor. The first tests were also carried out to functionalise the Chg planar waveguides with the aim of using them as (bio)sensors.

A selenide integrated platform working in the mid-infrared was designed, fabricated and optically characterized at 7.7 µm. Ge-Sb-Se multilayered structures were deposited by RF magnetron sputtering. Using i-line photolithography and fluorine-based reactive ion etching, ridge waveguides were processed as Y-junction, spiral and S-shape waveguides. Single-mode optical propagation at 7.7 µm was observed by optical near-field imaging and optical propagation losses of 2.5dB/cm are measured. Limits of detection of 14.2 ppm and 1.6 ppm for methane and nitrous oxide, respectively, could be potentially measured by using this platform as an evanescent field sensor. Hence, these technological, experimental and theoretical results represent a first step towards the development of an integrated optical sensor operating in the mid-infrared wavelength range.

International audienceA theoretical study of evanescent optical sensor for multipurpose detection in the Mid-Infrared of gases and pollutants in water is presented in this paper. The opto-geometrical parameters of the transducers - ridge waveguides - have been optimized in order to obtain the highest evanescent power factor for monomodal propagation in the Mid-Infrared. The highest sensitivity has been obtained for a configuration with an optimal length of waveguide L-ops = 4.3 cm for intrinsic propagation loss equal to 1 dB/cm. Then a spiral waveguide configuration is suggested to obtain this optical length path in a monolithic structure. A numerical example is also included using a ridge waveguide based on chalcogenide glasses (GeSbSe). In case of gas detection, a generic calculation of the minima concentrations to be detected as a function of the molar absorption for any working wavelength is presented. Extremely low limits of detection can be achieved due to the strong absorption coefficients of gases and chemical species in the Mid-Infrared spectral range, 268 ppb in case of carbon dioxide at lambda =4.3 p.m, 1.848 ppm and 781 ppb for methane at lambda=3.31 pm and at lambda=7.66 pm respectively. For the pollutants detection in water, an improvement of the integrated structure has been proposed to avoid water absorption in this spectral region by deposing a polymer (PIB) as waveguide superstrate, thus the limit of detection for toluene is 26 ppb at lambda=6.68 pm. These concentration minima that could be detected by the Mid-IR sensor are lower than the threshold limit values determined in the international environmental and health standards. Hence this integrated optical sensor may be considered as an attractive support tool in monitoring environmental and health fields. (C) 2016 Elsevier B.V. All rights reserved

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International audienceThe deposition of Ge25Sb10S65 and Ge25Sb10Se65 amorphous chalcogenide thin films was performed by radio-frequency magnetron sputtering and pulsed laser deposition technique. The deposited layers were characterized by studying their morphology, topography, chemical composition, structure, and optical functions permitting a direct comparison of two deposition methods for obtaining attractive amorphous chalcogenide films. Reactive ion etching was then used to pattern rib/ridge waveguides in sulfide and selenide films with low surface roughness, vertical sidewalls, and reasonable etching rate. Optical losses of fabricated waveguides were measured at 1550 nm with values better than 1 dB/cm obtained for sulfide/selenide films deposited by both techniques

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