Out-of-plane focusing grating couplers for silicon photonics integration with optical MRAM technology

We present the design methodology and experimental characterization of compact out-of-plane focusing grating couplers for integration with magnetoresistive random access memory technology. Focusing grating couplers have recently found attention as layer-couplers for photonic-electronic integration. The components we demonstrate are designed for a wavelength of 1550 nm, fabricated in a standard 220 nm SOI photonic platform and optimized given the fabrication restrictions for standard 193-nm UV lithography. For the first time, we extend the design based on the phase matching condition to a two-dimensional (2-D) grating design with two optical input ports. We further present the experimental characterization of the focusing behaviour by spatially probing the emitted beam with a tapered-and-lensed fiber and demonstrate the polarization controlling capabilities of the 2-D FGCs

Design optimization for energy-efficient pulse-switching networks in carrier-injection based Si-photonics

We compare pulse-switching operations in MZI- and ring-switches both experimentally and based on large-signal circuit simulations. With a modification in switch design and with optimization of phase modulator lengths, we show high-speed switches with potential for an over 3 dB improvement in energy consumption

Tensor-Based Preprocessing of Combined EEG/MEG Data

5 pagesInternational audienceDue to their good temporal resolution, electroencephalography (EEG) and magnetoencephalography (MEG) are two often used techniques for brain source analysis. In order to improve the results of source localization algorithms applied to EEG or MEG data, tensor-based preprocessing techniques can be used to separate the sources and reduce the noise. These methods are based on the Canonical Polyadic (CP) decomposition (also called Parafac) of space-time-frequency (STF) or space-time-wave-vector (STWV) data. In this paper, we analyze the combination of EEG and MEG data to enhance the performance of the tensor-based preprocessing. To this end, we consider the joint CP decomposition of two (or more) third order tensors with one or two identical loading matrices. We present the necessary modifications for several classical CP decomposition algorithms and examine the gain on performance in the EEG/MEG context by means of simulations

High resolution direction finding from rectangular higher order cumulant matrices: The rectangular 2Q-music algorithms

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Robust 3-way tensor decomposition and extended state Kalman filtering to extract fetal ECG

International audienceThis paper addresses the problem of fetal electrocardiogram (ECG) extraction from multichannel recordings. The proposed two-step method, which is applicable to as few as two channels, relies on (i) a deterministic tensor decomposition approach, (ii) a Kalman filtering. Tensor decomposition criteria that are robust to outliers are proposed and used to better track weak traces of the fetal ECG. Then, the state parameters used within an extended realistic nonlinear dynamic model for extraction of N ECGs from M mixtures of several ECGs and noise are estimated from the loading matrices provided by the first step. Application of the proposed method on actual data shows its significantly superior performance in comparison to the classic methods

Robust 3-way tensor decomposition and extended state Kalman filtering to extract fetal ECG

International audienceThis paper addresses the problem of fetal electrocardiogram (ECG) extraction from multichannel recordings. The proposed two-step method, which is applicable to as few as two channels, relies on (i) a deterministic tensor decomposition approach, (ii) a Kalman filtering. Tensor decomposition criteria that are robust to outliers are proposed and used to better track weak traces of the fetal ECG. Then, the state parameters used within an extended realistic nonlinear dynamic model for extraction of N ECGs from M mixtures of several ECGs and noise are estimated from the loading matrices provided by the first step. Application of the proposed method on actual data shows its significantly superior performance in comparison to the classic methods

Blind source separation of underdetermined mixtures of event-related sources

International audienceThis paper addresses the problem of blind source separation for underdetermined mixtures (i.e., more sources than sensors) of event-related sources that include quasi-periodic sources (e.g., electrocardiogram (ECG)), sources with synchronized trials (e.g., event-related potentials (ERP)), and amplitude-variant sources. The proposed method is based on two steps: (i) tensor decomposition for underdetermined source separation and (ii) signal extraction by Kalman filtering to recover the source dynamics. A tensor is constructed for each source by synchronizing on the ''event'' period of the corresponding signal and stacking different periods along the second dimension of the tensor. To cope with the interference from other sources that impede on the extraction of weak signals, two robust tensor decomposition methods are proposed and compared. Then, the state parameters used within a nonlinear dynamic model for the extraction of event-related sources from noisy mixtures are estimated from the loading matrices provided by the first step. The influence of different parameters on the robustness to outliers of the proposed method is examined by numerical simulations. Applied to clinical electroencephalogram (EEG), ECG and magnetocardiogram (MCG), the proposed method exhibits a significantly higher performance in terms of expected signal shape than classical source separation methods such as piCA and FastICA

Out-of-plane focussing polarization control grating couplers for photonic-spintronic integration

We demonstrate the first out-of-plane 2D focusing grating coupler (FGC), designed for compact photonic-spintronic integration allowing full polarization control of the emitted light. The couplers are designed for a standard 220nm-SOI platform and fabricated with 193 nm UV lithography. These couplers can find applicability as polarization (de)multiplexers, optical layer couplers or to realize optically enabled spintronic memory based on helicity dependent all-optical switching (AOS)[1,2]