Enhancing the nonlinear functionality of step-index silica fibers through the combination of thermal poling and 2D materials

Thermal poling, a technique to create permanently effective second-order susceptibility in silica optical fibers, has recently been improved by the discovery of an "induction poling" technique1 and the adoption of liquid electrodes2, allowing for poling fibers of any length and geometry. Nevertheless, the nonlinearity created via thermal poling is always limited by the ooelig;'(3)of the optical fiber material and by the maximum electric field that can be frozen inside the glass. For these reasons research is ongoing to determine routes for further improving the nonlinear effects due to the thermal poling process. In this work, we propose to enhance the effects of the thermal poling by exploiting the intrinsic nonlinear properties of some 2D materials3, which are deposited inside the cladding holes of a twin-hole silica fiber. The materials we focused on are 2D Transition Metal Chalcogenide (2D TMDC) MoS2 and WS2 and the technique adopted to realize the deposition inside the cladding channels of a twin-hole step index silica fiber consists of a thermal decomposition process4 of the precursor ammonium tetrathiomolybdate (NH4)2MoS4 in 6% H2/Ar flow. The technique has allowed us to uniformly coat the two cladding channels for a length of 25 cm with a film nominally consisting in a bi-layer of the 2D materials. A Raman based analysis has been used to test the morphology of the coating. The fiber deposited with 2D materials was later thermally poled and periodically erased via exposure to UV light to reach the QPM condition at a wavelength of 1550 nm. The effective oœ'(2) of the fiber was measured via SHG for both the deposited and the pristine fiber, showing an enhancement of the nonlinearity in favor of the deposited one. The phenomenon can be explained by the exploitation of a higher oœ'(3) seen by the pump wave due to the presence of the 2D layer deposited inside the cladding holes and opens the possibility of exploiting the higher intrinsic material oœ'(2), in case of a periodic patterning/synthesis of the TMDC.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Enhancement of nonlinear functionality of step-index silica fibers combining thermal poling and 2D materials deposition

This work proposes a new route to overcome the limits of the thermal poling technique for the creation of second order nonlinearity in conventional silica optical fibers. We prove that it is possible to enhance the nonlinear behavior of periodically poled fibers merging the effects of poling with the nonlinear intrinsic properties of some materials, such as MoS2, which are deposited inside the cladding holes of a twin-hole silica fiber. The optical waves involved in a second harmonic generation process partially overlap inside the thin film of the nonlinear material and exploit its higher third order susceptibility to produce an enhanced SHG.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The Gene Ontology resource: enriching a GOld mine

The Gene Ontology Consortium (GOC) provides the most comprehensive resource currently available for computable knowledge regarding the functions of genes and gene products. Here, we report the advances of the consortium over the past two years. The new GO-CAM annotation framework was notably improved, and we formalized the model with a computational schema to check and validate the rapidly increasing repository of 2838 GO-CAMs. In addition, we describe the impacts of several collaborations to refine GO and report a 10% increase in the number of GO annotations, a 25% increase in annotated gene products, and over 9,400 new scientific articles annotated. As the project matures, we continue our efforts to review older annotations in light of newer findings, and, to maintain consistency with other ontologies. As a result, 20 000 annotations derived from experimental data were reviewed, corresponding to 2.5% of experimental GO annotations. The website (http://geneontology.org) was redesigned for quick access to documentation, downloads and tools. To maintain an accurate resource and support traceability and reproducibility, we have made available a historical archive covering the past 15 years of GO data with a consistent format and file structure for both the ontology and annotations