Low-threshold power and tunable integrated optical limiter based on an ultracompact VO2/Si waveguide

[EN] Optical limiters are nonlinear devices that encompass applications from device protection to activation functionalities in neural networks. In this work, we report an optical limiter on silicon photonics based on an ultracompact VO2/Si waveguide. Our 20-¿m-long experimental device features a thermal tunable threshold power of only ~3.5 mW while being spectrally broadband. Our work provides a new pathway to achieve integrated optical limiters for dense and low-power photonic integrated circuits.This study was supported by Grant Nos. PID2019- 111460GB-I00 and FPU17/04224 funded by MCIN/AEI/ 10.13039/501100011033 and, by ESF Investing in your future; Grant funded by FEDER/Ministerio de Ciencia e InnovaciónAgencia Estatal de Investigación/Ref.ICTS-2017-28-UPV-9; PROMETEO Program (Ref.2019/123)-Generalitat Valenciana; and Action co-financed by the European Union through the European Regional Development Fund (ERDF) operational program for the Valencian Community 2014-2020. The authors also thank David Zurita for his help with the experimental setup and Pía Homm for the sample preparation.Parra Gómez, J.; Navarro-Arenas, J.; Menghini, M.; Recaman, M.; Pierre-Locquet, J.; Sanchis Kilders, P. (2021). Low-threshold power and tunable integrated optical limiter based on an ultracompact VO2/Si waveguide. APL Photonics. 6(12):1-6. https://doi.org/10.1063/5.0071395S1661

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Trends and challenges in diabetes for middle-income countries: Evidence from Mexico

The epidemiological and economic burden of diabetes poses one of the main challenges for health systems worldwide. This is particularly relevant in middle-income countries because of the constant growing trends that have been observed in recent years. In order to identify trends and challenges on epidemiological and economic burden from diabetes in a middle-income country we developed a longitudinal analysis on costs and trends in the number of cases of diabetes in Mexico. The study population included total annual cases of diabetes at national level. Regarding the annual cumulative incidence for 2016 versus 2018, depending on the institution there is an increase of 9–13% (p < 0.001). Comparing the economic burden from incidence in 2016 versus 2018 (p < 0.05), there is a 26% increase. The total amount for diabetes in 2017 (US dollars) was $9,684,780,574. It includes$ 4,292,085,964 in direct costs and $5,392,694,610 in indirect costs. The total direct costs are:$ 510,986,406 for uninsured population; $1,416,132,058 for insured population;$ 2,235,969,330 for users’ pockets. This is an example of what is happening in the management of diabetes care in middle-income countries and we suggest review and rethinking strategies of prevention, planning, organisation and resource allocation

MBE Grown Vanadium Oxide Thin Films for Enhanced Non‐Enzymatic Glucose Sensing

info:eu-repo/semantics/publishe

Optical and electrical performance of rear side epitaxial emitters for bifacial silicon solar cell application

© 2019 Elsevier B.V. In this work we investigated the optical and electrical performance of p-type epitaxial layers as the rear emitter of bifacial n-type PERT solar cells. In the first part of this paper, the surface morphology of epitaxial layers grown on textured surfaces is studied. Because of the epitaxial growth, a pyramids-rounding effect is observed as a result of {311} and {911} facet propagation. The growth pattern was quantified and modelled. In the second part of this paper, the optical performance of semi-device test structures is evaluated. The trend of the optical results in bifacial solar cell structures indicates that a final pyramid angle at the rear side around 20° gives the maximum light absorption in the wafer substrate. In this work we demonstrate that the epitaxial growth of the emitter on the textured rear side of these devices can already give a pyramid angle of 25° without having to introduce any additional polishing steps to modify the morphology of the textured surface. In the last part of this paper, we present the electrical results for semi-device structures created to quantify the recombination losses in the passivated and metallized regions of those p-type epitaxial emitters. These results indicate that by introducing a rear epitaxial emitter in the bifacial n-type PERT cell structure, we can increase the implied V oc up to 17 mV compared to a diffused emitter with the same sheet resistance.status: publishe

Epitaxial growth of V2O3 thin films on Si(111) by molecular beam epitaxy

Vanadium sesquioxide (V2O3) is a strongly correlated electron material exhibiting two distinct metal–insulator transitions that can be tuned via strain, doping, or pressure, making it an interesting material for new-generation sensors or smart devices. For this purpose, it is required to achieve well-ordered epitaxial thin film growth with high-quality electrical and optical properties on technologically relevant substrates. We report the successful growth of epitaxial thin films of V2O3 via molecular beam epitaxy, in the paramagnetic insulating (PI) phase on the (111) plane of silicon, by tailoring the growth conditions. Extensive electrical, structural, and morphological characterization both in situ and ex situ has been performed on all samples. The structural analysis reveals that temperature plays a more impactful role in affecting the thin film microstructures than the oxygen partial pressure. When the epitaxy of V2O3 occurs on the unoxidized (111) plane of silicon, four equivalent epitaxial domains begin to form, leading to twin boundaries in the bulk of the film. The considerable lattice mismatch between silicon and V2O3 induces the growth of the corundum PI phase. Lastly, small deviations from stoichiometry due to different oxygen inflow during growth alter significantly the resistivity change upon cooling