Design of Radiation-Hardened Rare-Earth Doped Amplifiers Through a Coupled Experiment/Simulation Approach

We present an approach coupling a limited experimental number of tests with numerical simulations regarding the design of radiation-hardened (RH) rare earth (RE)-doped fiber amplifiers. Radiation tests are done on RE-doped fiber samples in order to measure and assess the values of the principal input parameters requested by the simulation tool based on particle swarm optimization (PSO) approach. The proposed simulation procedure is validated by comparing the calculation results with the measured degradations of two amplifiers made with standard and RH RE-doped optical fibers, respectively. After validation, the numerical code is used to theoretically investigate the influence of some amplifier design parameters on its sensitivity to radiations. Simulations show that the RE-doped fiber length used in the amplifier needs to be adjusted to optimize the amplifier performance over the whole space mission profile rather than to obtain the maximal amplification efficiency before its integration in the harsh environment. By combining this coupled approach with the newly-developed RH RE-doped fibers, fiber-based amplifiers nearly insensitive to space environment may be designed in the future

Exploiting synchrotron X-ray tomography for a novel insight into flax-fibre defects ultrastructure

Flax fibres are valuable reinforcements for tomorrow's composites. However, defects called kink-bands, which mainly appear on fibres during the extraction and transformation phases, might affect their mechanical properties. Defects induced pores, within the kink-band are investigated in this work. They were morphologically explored using synchrotron phase-contrast X-ray microtomography, a technique that displays a sharp 3D representation of the pores. The study highlights the link between kink-bands and secondary cell wall ultrastructure. Pores are organised concentrically around the lumen, and their low thickness suggest that they are located at the interface between cellulose layers within S2 (G) layer. Moreover, the pores inclination with reference to the lumen axis follows the typical microfibrillar angle changes observed in the literature in the kink-band region. The volumes of the pores were measured, and a local increase in porosity was revealed in zones where defects are most severe along the fibre.Comment: 12 pages, 6 figures. Accepted for publication in Industrial Crops and Products (ISSN 0926-6690

Réseau de Bragg fibré pour le filtrage à bande étroite de l'émission autour de 400 nm d'une diode laser InGaN

National audienceNous rapportons la conception de réseaux de Bragg fibrés et présentons le résultat obtenu après montage d'un réseau utilisé comme réflecteur externe d'une diode laser InGaN afin d'en affiner le spectre jusqu'à obtenir une émission monomode longitudinale

Post-treatment of DBR fibre lasers for enhanced beat-frequency in dual-polarization operation

International audienceUV photo-ablation provides an efficient and reproducible means to control the birefringence of a dual-frequency DBR fiber laser. The resulting beat note can be finely tuned by real-time measurement during the process from typically 100 MHz to about 6 GHz, independently of the active medium length

Dual-polarization DFB fiber laser stabilized by frequency-shifted feedback

International audienceThe beat frequency of 1.5 μm dual polarization DFB fiber lasers is shown to be stabilized by means of an optical frequency-shifted feedback (FSF) loop. It leads to an optically carried RF source with sub-Hz linewidth

Réseau de Bragg fibré pour le filtrage à bande étroite de l'émission autour de 400 nm d'une diode laser InGaN

National audienceNous rapportons la conception de réseaux de Bragg fibrés et présentons le résultat obtenu après montage d'un réseau utilisé comme réflecteur externe d'une diode laser InGaN afin d'en affiner le spectre jusqu'à obtenir une émission monomode longitudinale

Validation of the McCumber theory in a wide temperature range for Er3+ emission cross section calculation in optical fibers

International audienceIn this paper, we investigate the temperature dependence of the Er3+ emission and absorption cross sections in aluminosilicate optical fibers. We also demonstrate that the McCumber theory can be used to accurately predict the temperature effect on the emission cross section spectrum up to 500°C contrary to the literature statement. For this, the measured absorption spectra at the considered temperature in a range of ~ [23-500 °C] has to be used as an input parameter for McCumber theory

Delay-induced instability in phase-locked dual-polarization distributed-feedback fiber lasers

International audienceWe study experimentally and theoretically a dual-polarization fiber laser submitted to time-delayed frequency-shifted optical feedback. In addition to the usual frequency-locking regime that is expected when the frequency shift is close to the polarization beat frequency, we observe at high pumping rates a dynamical pulsing regime inside the locking range. This regime is experimentally evidenced in a full-fibered experiment based on an erbium-doped distributed-feedback fiber laser in which polarization beat frequency is about 1 GHz. A rate-equation model including the frequency-shifted feedback term reproduces well the experimental bifurcation maps, provided that both the time delay and a phase-amplitude coupling parameter (α factor) are taken into account. The impact on microwave-photonics applications is discussed

Lasers à fibre bifréquences stabilisés par réinjection optique

National audienceLes lasers à fibre DFB bi-polarisation sont des sources hétérodynes de choix pour les senseurs ou la photonique microonde. Dans ce cadre, nous démontrons et étudions la stabilisation du battement à 1 GHz d'un laser DFB bifréquence au moyen d'une boucle de réinjection optique décalée en fréquence. La largeur de la plage d'accrochage du battement sur un synthétiseur est proportionnelle au taux de réinjection. Le bruit de phase du battement stabilisé est de –104 dBc/Hz à 1 kHz. Des simulations numériques indiquent que la forte dissymétrie de la plage d'accrochage, observée expérimentalement, peut s'expliquer par un couplage phase-amplitude important (α > 1)