Single-frequency, pulsed Yb3+-doped multicomponent phosphate power fiber amplifier

High-power, single-frequency, pulsed fiber amplifiers are required in light detection and ranging, coherent laser detection, and remote sensing applications to reach long range within a short acquisition time. However, the power-scaling of these amplifiers is limited by nonlinearities generated in the optical fibers, in particular by stimulated Brillouin scattering (SBS). In this regard, the use of multicomponent phosphate glasses maximizes the energy extraction and minimizes nonlinearities. Here, we present the development of a single-stage, hybrid, pulsed fiber amplifier using a custom-made multicomponent Yb-doped phosphate fiber. The performance of the phosphate fiber was compared to a commercial Yb-doped silica fiber. While the latter showed SBS limitation at nearly 6.5 kW for 40 cm length, the maximum achieved output peak power for the multicomponent Yb-doped phosphate fiber was 11.7 kW for 9 ns pulses using only 20 cm with no sign of SBS

High-power laser testing of calcium-phosphate-based bioresorbable optical fibers

Silica optical fibers are employed in endoscopy and related minimally invasive medical methods thanks to their good transparency and flexibility. Although silicon oxide is a biocompatible material, its use involves a serious health risk due to its fragility and the fact that potential fiber fragments can freely move inside the body without the possibility of being detected by conventional methods such as X-ray imaging. A possible solution to this issue can be the development of optical fibers based on bioresorbable (i.e., biodegradable and biocompatible) materials, which exhibit the important benefit of not having to be explanted after their functionality has expired. The optical power transmission tests of recently developed single-mode (SM) and multi-mode (MM) bioresorbable optical fibers based on calcium-phosphate glasses (CPGs) are here reported. A continuous-wave (CW) fiber laser at 1080 nm with output power up to 13 W and picosecond laser sources at 515 and 1030 nm with MW pulse peak power were used to test the transmission capabilities of the CPG fibers. No degradation of the CPG fibers transmission under long-term illumination by CW laser was observed. A laser-induced damage threshold (LIDT) at a fluence higher than 0.17 J/cm2 was assessed with the picosecond laser sources

Phosphate glass-based microstructured optical fibers with hole and core for biomedical applications

Bioresorbable phosphate glasses are an excellent alternative to conventional silicate-based glass systems for biomedical applications. These glasses can have tailorable bioresorbability and mechanical properties, a wide range of transparency windows (from 300 to 2600 nm), and are of great interest for biophotonic devices. The present work investigates the feasibility of fabricating a microstructured bioresorbable optical fiber combined with a microfluidic channel. Extrusion and stack-and-draw techniques are used to manufacture the microstructured optical fiber capable of guiding light and liquid simultaneously. An optimized extrusion procedure allowed fabricating preforms with the lowest bending and tapering possible. The preform was drawn to 130 and 230 μm diameter fibers. Light guide and attenuation loss were characterized, and the microfluidic channel was tested for liquid delivery. The proposed approach demonstrates the vast potentiality of such microstructured fiber that could be used as a theranostics device to be employed in specific areas inside the body without needing a removal procedure

ß-Glucuronidase activity in transgenic and non-transgenic tobacco cells: specific elimination of plant inhibitors and minimization of endogenous GUS background

Bacterial beta-glucuronidase is often introduced into plants as a reporter gene fused to constitutive or inducible promoters, However, the presence of both endogenous inhibitors of GUS activity and endogenous GUS enzymes in transgenic plants could lead to an underestimation of GUS. In this paper, a decrease of the V-m values and a greater affinity (K-m) of the GUS enzyme for its substrate (p-NPG) has been recorded when increasing amounts of protein from untransformed tobacco cells has been added to the pure beta-glucuronidase. The observed inhibition is not competitive and can be completely removed when the tobacco extracts are passed through Sephadex G-25 spin columns prior to the assays. After such a treatment, the activity of E. coli GUS in transgenic tobacco cells (constitutive or inducible systems) was stimulated by a factor 1.2 or 2 for p-NPG or 4-MUG substrates, respectively. This method was also effective in suppressing the endogenous GUS or GUS-like activity which can interfere with the activity originating from the introduced GUS gene

Novel Er3+ doped phosphate glass-ceramics for photonics

In this invited proceeding, we report our latest results on the development of Er3+ doped phosphate glass-ceramics. Those new glass-ceramics were processed using different techniques, such as direct doping of particles into the glass melt and glass-ceramics methods. First, we explain the challenges to balance the survival and dispersion of Er3+ doped particles when preparing phosphate glass-ceramics using the direct doping of particles. Then, we discuss the impact of the glass crystallization on the luminescence properties of Er3+ ions

A calibration free radiation driven model for estimating actual evapotranspiration of mountain grasslands (CLIME-MG)

Ecosystems in the Alps are considered hotspots of climate and land use change. In addition, alpine regions are usually characterized by complex morphologies, which make measurement (especially in the long term) of states and fluxes of water, energy and matter particularly challenging. Therefore, there is a limited availability of information and modelling tools to characterize actual ecosystem conditions, and to simulate future scenarios. Despite the fact that in high altitude areas meteorological forcing is extremely variable in space and time, much of the variability of actual evapotranspiration (AET) in the above-mentioned regions is largely related to land surface properties such as aspect, shadowing and slope. Therefore, a simple, radiation driven, calibration free, bucket hydrological model for predicting AET and estimating the soil-water balance is proposed here (i.e. CLIME-MG). Conventional meteorological data from a network of automatic weather stations together with a 10 m digital terrain model (aggregated at 30 m), and a land cover map are used to inform the model. All the parameters and values required are obtained or calculated from data provided in literature. CLIME-MG has proved to perform well for AET modelling of mountain grassland. The model is validated both temporally and spatially. Temporal validation of AET is performed using eddy-covariance datasets from two different high mountain sites: a sunny and steep abandoned pasture facing S-E at an altitude of 1730 m, and a meadow with a S-SE aspect located at an altitude of 2555 m. Spatial validation is performed by comparing CLIME-MG simulations with the Landsat-based METRIC model evapotranspiration output. Results show good daily temporal performance, especially in wetter periods with recurring rainfall events. Sensitivity of the correlation coefficient between measured and modeled AET values to some key parameters such as effective porosity, and the vegetation and stress coefficients was found to be quite low. Spatial validation of hourly results shows SPAEF values in the range 0.21-0.34 between the outputs of the two models (with a similar spatial structure ruled by the DTM). Boxplots of deviations between CLIME and METRIC with respect to morphological characteristics has highlighted some dependency on elevation and slope (but not on aspect and soil depth); this suggests an opportunity to refine the modelisation of the grassland AET processes. Finally, spatial results demonstrated the non-sensitivity of the proposed model to local elevation and to the distance from the meteorological stations