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International audience; The voids-fiber Bragg gratings (FBGs) are manufactured point by point by focalizing an infrared femtosecond laser in a small fraction of the core and creating a microscopic void. This makes these gratings very resistant and stable to high temperatures. However, until today, only very few tests under radiation have been performed on these FBGs. A complete study on the radiation response of this grating technology under X-rays is here presented, highlighting the dependence of its radiation response on dose, dose rate, irradiation temperature, and preirradiation treatment.

International audience; Fiber Bragg Grating (FBG) based sensors are nowadays used for several applications, but, even if they present advantages for their incorporation into radiation environments, commercial-off-the-shelf devices cannot still be used in harsh conditions. We recently reported a procedure for fabricating FBGs resistant to severe constraints combining both high radiation doses up to MGy levels and operation temperatures exceeding 200°C (RadHard FBGs). Following these results, the European project HOBAN was granted by Kic InnoEnergy with the aim of developing and marketing FBG-based temperature and strain monitoring systems suitable for harsh nuclear environments (350°C temperature and MGy dose levels), with their associated instrumentation devices. In this framework, we present an accurate study about the robustness of the radiation-response of these RadHard FBGs against the main grating inscription parameters. Up to the accumulated X-ray dose of 1 MGy(SiO2), no significant radiation induced Bragg wavelength shift is observed meaning that radiations induce errors below ± 0.4°C in the temperature estimation. Moreover, a study about the dose-rate dependence (1 to 50 Gy/s) of the gratings response is also reported and confirms the high radiation hardness of our RadHard FBGs at all dose rates.

International audience; In the framework of the HOBAN collaborative project funded by KIC InnoEnergy, radiation-hardened fiber Bragg gratings (FBGs) are developed to withstand high levels of radiation dose at high temperatures for their implementation in temperature and strain sensors for nuclear facilities, accelerators or space. This paper presents Gamma radiation test results obtained at room and elevated temperature in hardened FBGs as well as in the optical fibers used for their production. It is shown that radiation-induced Bragg wavelength shift is below ±2 pm corresponding to ±0.2 °C and does not influence the sensor performance even after a total dose of 200 kGy(SiO2) and operating temperature up to 350 °C.

In the framework of a KIC InnoEnergy funded project radiation-hardened Fiber Bragg Gratings (FBG) are developed to withstand high levels of radiation dose at high temperatures for their implementation in temperature- and strain sensors for nuclear facilities, accelerators or space. This paper presents gamma radiation test results obtained at room and elevated temperature in hardened FBGs as well as in the optical fibers used for their production. It is shown that radiation-induced Bragg wavelength shift (BWS) is below ±2 pm corresponding to ±0.2°C and does not influence the sensor performance even after a total dose of 200 kGy(SiO2) and operating temperature up to 350°C.

Ion-exchange technology on glass has been successfully used for more than 20 years to realize dependable and low-cost passive and active integrated optic devices on silicate or phosphate glasses for the optical telecommunication systems operating around λ = 1.5 μm. However, the recent developments of integrated optics instruments for astronomical interferometers or biological sensors have required an increase of the devices operation range towards the mid-infrared. For these reasons, we present in this paper the development and the realization of single-mode waveguides by means of a binary ion-exchange on a germanate glass (BGA-G115 form Kigre Inc.) which transparency window reaches λ = 4 μm. A complete study of the silver ion diffusion in this glass matrix has been performed allowing the determination of silver and sodium ion diffusion coefficients as well as the value of the maximum refractive index change. Using these data, simulations were carried-out showing that an ion-exchange of 90 min in a 0.03AgNO 3 –0.97NaNO 3 molten salt at a temperature of 330 °C would allow the realization of single-mode channel waveguides at λ = 1.55 μm. To demonstrate this on BGA-G115, a specific technological process based on the deposition of a polysilicon masking layer has been implemented. Single-mode channel waveguides, with a 2.5 μm diffusion window width, have thus been realized and characterized at the wavelength of 1.55 μm. Modal size has been measured to be 10 ± 1 μm × 7 ± 1 μm for propagation losses of 1.2 ± 0.5 dB/cm for a 2 ± 0.1 cm long device.

Modal filtering is based on the capability of single-mode waveguides to transmit only one complex amplitude function to eliminate virtually any perturbation of the interfering wavefronts, thus making very high rejection ratios possible in a nulling interferometer. In the present paper we focus on the progress of Integrated Optics in the thermal infrared [6-20μm] range, one of the two candidate technologies for the fabrication of Modal Filters, together with fiber optics. In conclusion of the European Space Agency's (ESA) "Integrated Optics for Darwin" activity, etched layers of chalcogenide material deposited on chalcogenide glass substrates was selected among four candidates as the technology with the best potential to simultaneously meet the filtering efficiency, absolute and spectral transmission, and beam coupling requirements. ESA's new "Integrated Optics" activity started at mid-2007 with the purpose of improving the technology until compliant prototypes can be manufactured and validated, expectedly by the end of 2009. The present paper aims at introducing the project and the components requirements and functions. The selected materials and preliminary designs, as well as the experimental validation logic and test benches are presented. More details are provided on the progress of the main technology: vacuum deposition in the co-evaporation mode and subsequent etching of chalcogenide layers. In addition, preliminary investigations of an alternative technology based on burying a chalcogenide optical fiber core into a chalcogenide substrate are presented. Specific developments of anti-reflective solutions designed for the mitigation of Fresnel losses at the input and output surface of the components are also introduced.

Ion-exchange on glass is now a mature integrated optics technology. Indeed, many devices such as wavelength multiplexers, splitters, optical amplifiers, lasers or sensors have been already realized. The challenge now is to integrate all these functions on a single chip. Two different paths can be used to achieve this goal: the first one consists of a reduction of the waveguides’ dimensions by an increase of the refractive index change, whereas the second one, which is addressed in this paper, is based on the realization of multilayered devices. Because ion-exchange on glass allows manufacturing either surface or buried waveguides, this technology is well adapted for 3D integration. However, to realize integrated optical devices with two different layers, it is mandatory to prevent any parasitic light transfer between them. This condition can be fulfilled if the top and bottom waveguides are sufficiently separated. In this article, we present the development of ion-exchanged waveguides deeply buried into a glass substrate and their application to 3D integrated devices. Deeply buried waveguides have been realized by means of a two steps silver–sodium ion-exchange on a dedicated custom made silicate glass. First, a thermal ion-exchange has been carried out at 330 °C during 2 min in a 0.8NaNO3–0.2AgNO3 molten salt in order to create the core of the waveguide. Then, this core has been buried into the glass substrate by applying an electric field of 450 kV/m during 1 h 30 min in a sodium nitrate solution at 260 °C. The obtained waveguide has been measured to be 22 μm under the glass surface. It is singlemode at λ = 1.55 μm. In order to prove the good isolation between this waveguide and the surface, a top layer has been added to the device by the realization of surface channel waveguides through a thermal ion-exchange performed in a 0.8NaNO3–0.2AgNO3 molten salt at 330 °C during 2 min. The near-field observation of the device output has shown no coupling between the top and bottom layers demonstrating therefore the feasibility of 3D integrated optical devices by means of ion-exchange on glass.

In this letter, the fabrication and characterization of a broadband 980-nm/1550-nm wavelength (de)multiplexer is described. This device is adapted for pump/signal multiplexing in erbium-doped waveguide amplifiers. The structure chosen is a segmented asymmetric Y-junction, which can be fabricated with one masking level using silver-sodium ion-exchange on a silicate glass substrate. The nonresonant behavior of the Y-junction allows a wideband multiplexing with isolations increasing from (9.7plusmn0.1) dB at 1500 nm to (15plusmn0.1) dB at 1630 nm and (26plusmn1) dB at 980 nm. The total insertion losses are (2.8plusmn0.1) dB at 980 nm and (3.3plusmn0.2) dB between 1500 and 1630 nm

International audience; Ion-exchange on glass has been successfully used for more than twenty years to realize integrated optics devices such as wavelength multiplexers, splitters, optical amplifiers, lasers or sensors. One of the major issue is today to integrate more functions on a single chip which is usually realized be reducing the dimensions of the waveguides. Nonetheless this reduction is intrinsically limited by the maximum index variation achievable. For this reason, we propose and investigate in this article the realization of 3D structures where waveguides are integrated vertically instead of horizontally. Based on the selective burial of ion-exchanged waveguides and the cascading of multiple ion-exchanges, the realization of ”vertical” asymmetric and symmetric Y-junctions have been investigated theoretically.

Broadband wavelength (de)multiplexers play a key role in different fields of integrated optics. In particular, the development of Erbium Doped Waveguide Amplifiers (EDWA) requires efficient integrated pump/signal multiplexers. In this article, the design and the realization of a 980 nm/1550 nm wavelength multiplexer based on a segmented asymmetric Y junction made by silver/sodium ion exchange on glass is discussed. We first present the behavior of an asymmetric Y junction, in order to describe its use as a wavelength (de)multiplexer. Then, the index averaging principle of a segmented waveguide is detailed, as well as its application in the design of one of the asymmetric Y junction branches. The design of a segmented asymmetric Y junction is then described, as well as its BPM simulations results. They show isolation of 33 dB at 980 nm and 25.6 dB at 1550 nm with excess losses of 2.6 dB at 980 nm and 1.3 dB at 1550 nm. In a second time, we present the realization of this component using a Silver/Sodium ion-exchange on glass. For λ = 980 nm, the isolation measured is (31 ± 1) dB, and in the third communication window, the isolation increases from (11.5±0.25) dB at λ = 1500 nm to (15.5±0.25) dB at λ = 1600 nm. The broadband operation is only limited by the modal characteristics of the waveguides composing the junction and ranges from 1500 nm to 1650 nm. Total insertion losses measured at 980nm are (2.63±0.1) dB. Around 1550 nm, losses vary from (3.6 ± 0.1) dB at the 1500 nm wavelength to (4.6 ± 0.1) dB at 1600 nm.

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The realisation and characterisation of periodic segmented waveguides made by Ag+/Na+ ion-exchange on glass is presented. In particular, the averaging effects provided by the segmentation are analysed using the measurement of the cutoff wavelengths of the fundamental mode. Numerical calculations are used to evaluate the equivalent index contrast of a continuous waveguide from cutoff wavelength. It is found that the model predicting the index averaging effect of periodically segmented waveguides is valid if the duty cycle of the segmented waveguide is corrected by a term that takes into account the longitudinal ion diffusion.

Dans cet article, on rapporte la realisation de guides d’ondes segmentes enterres realises en optique integree sur verre. Avec la technique de l’echange d’ions, on a pu obtenir des guides monomodes sur les trois fenetres des telecommunications optiques, de bonne qualite, avec des periodes de segmentation compris entre 3μm et 100μm et des taux de vide compris entre 0, 25 et 0, 90. Les effets de la segmentation sont evidents dans la taille modale et dans le deplacement de la longueur d’onde de coupure du deuxieme mode confine dans le guide.