Photonic Neural Networks and Optics-informed Deep Learning Fundamentals

The recent explosive compute growth, mainly fueled by the boost of AI and DNNs, is currently instigating the demand for a novel computing paradigm that can overcome the insurmountable barriers imposed by conventional electronic computing architectures. PNNs implemented on silicon integration platforms stand out as a promising candidate to endow NN hardware, offering the potential for energy efficient and ultra-fast computations through the utilization of the unique primitives of photonics i.e. energy efficiency, THz bandwidth and low-latency. Thus far, several demonstrations have revealed the huge potential of PNNs in performing both linear and non-linear NN operations at unparalleled speed and energy consumption metrics. Transforming this potential into a tangible reality for DL applications requires, however, a deep understanding of the basic PNN principles, requirements and challenges across all constituent architectural, technological and training aspects. In this tutorial, we, initially, review the principles of DNNs along with their fundamental building blocks, analyzing also the key mathematical operations needed for their computation in a photonic hardware. Then, we investigate, through an intuitive mathematical analysis, the interdependence of bit precision and energy efficiency in analog photonic circuitry, discussing the opportunities and challenges of PNNs. Followingly, a performance overview of PNN architectures, weight technologies and activation functions is presented, summarizing their impact in speed, scalability and power consumption. Finally, we provide an holistic overview of the optics-informed NN training framework that incorporates the physical properties of photonic building blocks into the training process in order to improve the NN classification accuracy and effectively elevate neuromorphic photonic hardware into high-performance DL computational settings

A 160Gb/s (4x40) WDM O-band Tx subassembly using a 4-ch array of silicon rings co-packaged with a SiGe BiCMOS IC driver

We present a 400 (8×50) Gb/s-capable RM-based Si-photonic WDM O-band TxRx with 1.17nm channel spacing for high-speed optical interconnects and demonstrate successful 50Gb/s-NRZ TxRx operation achieving a ~4.5dB Tx extinction ratio under 2.15Vpp drive

Temperature and wavelength drift tolerant WDM transmission and routing in on-chip silicon photonic interconnects

We demonstrate a temperature and wavelength shift resilient silicon transmission and routing interconnect system suitable for multi-socket interconnects, utilizing a dual-strategy CLIPP feedback circuitry that safeguards the operating point of the constituent photonic building blocks along the entire on-chip transmission-multiplexing-routing chain. The control circuit leverages a novel control power-independent and calibration-free locking strategy that exploits the 2nd derivative of ring resonator modulators (RMs) transfer function to lock them close to the point of minimum transmission penalty. The system performance was evaluated on an integrated Silicon Photonics 2-socket demonstrator, enforcing control over a chain of RM-MUX-AWGR resonant structures and stressed against thermal and wavelength shift perturbations. The thermal and wavelength stress tests ranged from 27 degrees C to 36 degrees C and 1309.90 nm to 1310.85 nm and revealed average eye diagrams Q-factor values of 5.8 and 5.9 respectively, validating the system robustness to unstable environments and fabrication variations. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreemen

Co-Package Technology Platform for Low-Power and Low-Cost Data Centers

We report recent advances in photonic–electronic integration developed in the European research project L3MATRIX. The aim of the project was to demonstrate the basic building blocks of a co-packaged optical system. Two-dimensional silicon photonics arrays with 64 modulators were fabricated. Novel modulation schemes based on slow light modulation were developed to assist in achieving an efficient performance of the module. Integration of DFB laser sources within each cell in the matrix was demonstrated as well using wafer bonding between the InP and SOI wafers. Improved semiconductor quantum dot MBE growth, characterization and gain stack designs were developed. Packaging of these 2D photonic arrays in a chiplet configuration was demonstrated using a vertical integration approach in which the optical interconnect matrix was flip-chip assembled on top of a CMOS mimic chip with 2D vertical fiber coupling. The optical chiplet was further assembled on a substrate to facilitate integration with the multi-chip module of the co-packaged system with a switch surrounded by several such optical chiplets. We summarize the features of the L3MATRIX co-package technology platform and its holistic toolbox of technologies to address the next generation of computing challenges

Bouncing back : the wellbeing of children in international child abduction cases

This report contains the results of a three-part research project conducted in the framework of the project Enhancing the Well-being of Children in Cases of International Child Abduction (eWELL). Part I contains an overview of the results of a quantitative survey conducted among parents who have been in a situation of international parental child abduction. The quantitative survey data collection was financed by the European Commission and was undertaken by the University of Antwerp in collaboration with Centrum IKO, CFPE-Enfant Disparus, Child Focus, the French Central Authority and Missing Children Europe (MCE, the European umbrella organization for missing children). Part II provides an overview of the qualitative interview results conducted with children who were taken by to another country by one parent without the consent of the other. The qualitative data collection was co-financed by the European Commission and undertaken by the University of Antwerp, Centrum IKO, Child Focus, CFPE-Enfant Disparus, and in collaboration with the French Central Authority and Missing Children Europe (MCE, the European umbrella organization for missing children). Part III examines international parental child abduction court rulings, jurisdictions and the application of Art. 13 (2) of the 1980 Hague Convention on the Civil Aspects of International Child Abduction in Belgium, France and the Netherlands. It discusses age and maturity attainment and assessment; the involvement of intermediaries; the definition of the child’s objections to return and other relevant matters

The effects of surgical expansion of the maxillary arch and its consequences for the incisor axis

Purpose: Reduced transverse maxillary dental arch width may be treated either by surgically supported rapid maxillary expansion (SRME) with conservative orthodontic appliances or by means of Le Fort I osteotomy (LFIO). Both are means of transverse maxillary expansion. Methods: Both surgical methods (SRME and LFIO) were evaluated with regard to the presurgical and postsurgical form of the maxillary dental arch and its consequences for the incisor axis by means of 32 dental casts and cephalometric analysis. Results: In both groups, anterior and posterior dental arch width showed significant changes after surgery, but changes in anterior dental arch width were less significant after LFIO (p = 0.004) than after SRME (p < 0.000; t-test). Cephalometric analysis (OK1/N1) did not show any significant differences between the two surgical methods (p = 0.1266; t-test). Anterior arch length was not reduced after LFIO but significantly reduced after SRME. Thus, the ideal elliptical shape of the dental arch was lost in the SRME group, which may impede esthetic outcome of the maxillary dental arch. Conclusion: Le Fort I osteotomy achieving direct transverse expansion should be favored over surgically supported rapid maxillary expansion if transverse expansion does not exceed 7 mm. (C) 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved