50 research outputs found

    On-chip beam rotators, polarizers and adiabatic mode converters through low-loss waveguides with variable cross-sections

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    Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss, in order to provide more degrees of freedom in manipulating propagating light. Here, we report on a new optical-fibres-compatible glass waveguide by femtosecond laser writing, namely spherical phase induced multi-core waveguide (SPIM-WG), which addresses this challenging task with three dimensional on-chip light control. Precise deformation of cross-sections is achievable along the waveguide, with shapes and sizes finely controllable of high resolution in both horizontal and vertical transversal directions. We observed that these waveguides have high refractive index contrast of 0.017, low propagation loss of 0.14 dB/cm, and very low coupling loss of 0.19 dB coupled from a single mode fibre. SPIM-WG devices were easily fabricated that were able to perform on-chip beam rotation through varying angles, or manipulate polarization state of propagating light for target wavelengths. We also demonstrated SPIM-WG mode converters that provide arbitrary adiabatic mode conversion with high efficiency between symmetric and asymmetric non-uniform modes; examples include circular, elliptical modes and asymmetric modes from ppKTP waveguides which are generally applied in frequency conversion and quantum light sources. Created inside optical glass, these waveguides and devices have the capability to operate across ultra-broad bands from visible to infrared wavelengths. The compatibility with optical fibre also paves the way toward packaged photonic integrated circuitry, which usually needs input and output fibre connections

    Defect engineering of silicon with ion pulses from laser acceleration

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    Defect engineering is foundational to classical electronic device development and for emerging quantum devices. Here, we report on defect engineering of silicon with ion pulses from a laser accelerator in the laser intensity range of 1019 W cm−2 and ion flux levels of up to 1022 ions cm−2 s−1, about five orders of magnitude higher than conventional ion implanters. Low energy ions from plasma expansion of the laser-foil target are implanted near the surface and then diffuse into silicon samples locally pre-heated by high energy ions from the same laser-ion pulse. Silicon crystals exfoliate in the areas of highest energy deposition. Color centers, predominantly W and G-centers, form directly in response to ion pulses without a subsequent annealing step. We find that the linewidth of G-centers increases with high ion flux faster than the linewidth of W-centers, consistent with density functional theory calculations of their electronic structure. Intense ion pulses from a laser-accelerator drive materials far from equilibrium and enable direct local defect engineering and high flux doping of semiconductors.This work was supported by the Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231. Experiments at the BELLA Center were enabled through facilities developed by HEP and LaserNetUS. TS and JGL gratefully acknowledge support by the coordinated research project “F11020” of the International Atomic Energy Agency (IAEA). LZT and JS were supported by the Molecular Foundry, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231Peer reviewe

    Supplementary Notes - Defect engineering of silicon with ion pulses from laser acceleration

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    14 pages. -- Supplementary Note 1. Time lapse movie showing evaporation of the aluminum foil mask during 100 shots. -- Supplementary Note 2. Photoluminescence (PL) and Secondary Ion Mass Spectrometry (SIMS) data correlation to PL data. -- Supplementary Note 3. Details on energy deposition and heat calculations. -- Supplementary Note 4. Details on Nuclear Reaction Analysis (NRA). -- Supplementary Note 5. Details on channeling Rutherford Backscattering (ch-RBS). -- Supplementary Note 6. Supplemental material on Density Functional Theory (DFT) calculations of G and W-centers in silicon.Peer reviewe

    HealtheSteps™ Study Protocol: a pragmatic randomized controlled trial promoting active living and healthy lifestyles in at-risk Canadian adults delivered in primary care and community-based clinics

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    Abstract Background Physical inactivity is one of the leading causes of chronic disease in Canadian adults. With less than 50% of Canadian adults reaching the recommended amount of daily physical activity, there is an urgent need for effective programs targeting this risk factor. HealtheSteps™ is a healthy lifestyle prescription program, developed from an extensive research base to address risk factors for chronic disease such as physical inactivity, sedentary behaviour and poor eating habits. HealtheSteps™ participants are provided with in-person lifestyle coaching and access to eHealth technologies delivered in community-based primary care clinics and health care organizations. Method/Design To determine the effectiveness of Healthesteps™, we will conduct a 6-month pragmatic randomized controlled trial with integrated process and economic evaluations of HealtheSteps™ in 5 clinic settings in Southwestern Ontario. 110 participants will be individually randomized (1:1; stratified by site) to either the intervention (HealtheSteps™ program) or comparator (Wait-list control). There are 3 phases of the HealtheSteps™ program, lasting 6 months each. The active phase consists of bi-monthly in-person coaching with access to a full suite of eHealth technology supports. During the maintenance phase I, the in-person coaching will be removed, but participants will still have access to the full suite of eHealth technology supports. In the final stage, maintenance phase II, access to the full suite of eHealth technology supports is removed and participants only have access to publicly available resources and tools. Discussion This trial aims to determine the effectiveness of the program in increasing physical activity levels and improving other health behaviours and indicators, the acceptability of the HealtheSteps™ program, and the direct cost for each person participating in the program as well as the costs associated with delivering the program at the different community sites. These results will inform future optimization and scaling up of the program into additional community-based primary care sites. Trial registration NCT02413385 (Clinicaltrials.gov). Date Registered: April 6, 2015

    Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

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    Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

    Diameter Quality Control of Nb3Sn Wires for MQXF Cables in the USA

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    The future of the external audit function

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    The future of the external audit function

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