Evaluation de méthodes CFD avec prise en compte de la transition laminaire-turbulent pour l'aéroélasticité des voilures laminaires

International audienceHigh fidelity aeroelastic simulations of laminar wings require an accurate prediction of the aerodynamic forces taking into account non-linear phenomena due to the laminar-turbulent transition. This paper proposes an evaluation of CFD RANS based methods associated with transition criteria or models for flight conditions of interest from an aeroelastic point of view (low and high incidences, transonic Mach numbers). This evaluation is carried out through comparisons with wind tunnel tests. The first step consists in assessing different models for steady transonic flow fields around a 2D laminar airfoil. The influence of crossflow transition on the aerodynamic response to a 3D wing oscillating in pitch is addressed in a second step for low speed flight conditions

Effect of mask discretization on performance of silicon arrayed waveguide gratings

We studied the impact of the lithography mask discretization on silicon arrayed waveguide grating (AWG) performance. When we decreased the mask grid from 5 to 1 nm, we observed an experimental improvement in crosstalk of 2.7-6 dB and cumulative crosstalk improvement of 1.2-5 dB, depending on the wavelength channel spacing and the number of output channels. We demonstrate the effect for the AWGs with 200-and 400-GHz channel spacing, with 4, 8, and 16 output wavelength channels. With 1-nm mask grid, the average crosstalk is -26 and -23 dB for 400- and 200-GHz devices, respectively. This is the lowest crosstalk for silicon AWGs reported to the best of our knowledge. A simulation study is performed by looking specifically at phase errors due to mask grid snapping (ignoring other phase error sources), which shows an expected improvement in crosstalk of 12 dB

Co-integration of Ge detectors and Si modulators in an advanced Si photonics platform

A Si photonics platform is described, co-integrating advanced passive components with Si modulators and Ge detectors. This platform is developed on a 200mm CMOS toolset, compatible with a 130nm CMOS baseline. The paper describes the process flow, and describes the performance of selected electro-optical devices to demonstrate the viability of the flow

Integrated optical frequency shifter on a silicon platform

An integrated optical frequency shifter on a standard silicon photonics platform completely fabricated in a CMOS pilot line and showing MHz frequency shifts with a sideband suppression ratio up to 36 dB is demonstrated

Light-Front Hadron Dynamics and AdS/CFT Correspondence

A remarkable consequence of the AdS/CFT correspondence is the nonperturbative derivation of dimensional counting rules for hard scattering processes. Using string/gauge duality we derive the QCD power behavior of light-front Fock-state hadronic wavefunctions for hard scattering in the large-$r$ region of the AdS space from the conformal isometries which determine the scaling of string states as we approach the boundary from the interior of AdS space. The nonperturbative scaling results are obtained for spin-zero and spin-\half hadrons and are extended to include the orbital angular momentum dependence of the constituents in the light-front Fock-expansion. The correspondence with string states is considered for hadronic states of arbitrary orbital angular momentum for a given hadron of spin $\leq 2$. We examine the implications of the color configuration of hadronic Fock-states for the QCD structure of scattering amplitudes at large $N_C$. Quark interchange amplitudes emerge as the dominant large $N_C$ scattering mechanisms for conformal QCD.Comment: LaTex, 21 pages. Additional references, corrected color factors, and corrected Dirac conformal dimension

III-V-on-silicon widely tunable laser realized using micro-transfer-printing

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Photonic integrated circuit based FMCW coherent LiDAR

We present the demonstration of an integrated Frequency Modulated Continuous Wave LiDAR on a silicon platform. The waveform calibration, the scanning system and the balanced detectors are implemented on chip. Detection and ranging of a moving hard target at up to 60 m with less than 5 mW of output power is demonstrated here

Fabrication-tolerant four-channel wavelength-division-multiplexing filter based on collectively tuned Si microrings

We demonstrate a robust, compact and low-loss four-channel wavelength-division multiplexing (WDM) filter based on cascaded double-ring resonators (2RR) in silicon. The flat-top channel response obtained by the second-order filter design is exploited to compensate for the detrimental effects of local fabrication variations and their associated phase errors on the ring-based filter response. Full wafer-scale characterization of a cascaded, four-channel 2RR filter with channel spacing of 300 GHz shows an average worst-case insertion loss below 1.5 dB and an average worst-case crosstalk below -18 dB across the wafer, representing a substantial improvement over a first-order based ring (1RR) design. The robust 2RR filter design enables the use of a simple collective thermal tuning mechanism to compensate for global fabrication variations as well as for global temperature fluctuations of the WDM filter, the WDM laser source, or both. Highly uniform collective heating is demonstrated using integrated doped silicon heaters. The compact filter footprint of less than 50 x 50 mu m(2) per channel enables straightforward scaling of the WDM channel count to 8 channels and beyond. Such low-loss collectively tuned ring-based WDM filters can prove beneficial in scaling the bandwidth density of chip-level silicon optical interconnects