Photonic integration enabling new multiplexing concepts in optical board-to-board and rack-to-rack interconnects

New broadband applications are causing the datacenters to proliferate, raising the bar for higher interconnection speeds. So far, optical board-to-board and rack-to-rack interconnects relied primarily on low-cost commodity optical components assembled in a single package. Although this concept proved successful in the first generations of optical-interconnect modules, scalability is a daunting issue as signaling rates extend beyond 25 Gb/s. In this paper we present our work towards the development of two technology platforms for migration beyond Infiniband enhanced data rate (EDR), introducing new concepts in board-to-board and rack-to-rack interconnects. The first platform is developed in the framework of MIRAGE European project and relies on proven VCSEL technology, exploiting the inherent cost, yield, reliability and power consumption advantages of VCSELs. Wavelength multiplexing, PAM-4 modulation and multi-core fiber (MCF) multiplexing are introduced by combining VCSELs with integrated Si and glass photonics as well as BiCMOS electronics. An in-plane MCF-to-SOI interface is demonstrated, allowing coupling from the MCF cores to 340x400 nm Si waveguides. Development of a low-power VCSEL driver with integrated feed-forward equalizer is reported, allowing PAM-4 modulation of a bandwidth-limited VCSEL beyond 25 Gbaud. The second platform, developed within the frames of the European project PHOXTROT, considers the use of modulation formats of increased complexity in the context of optical interconnects. Powered by the evolution of DSP technology and towards an integration path between inter and intra datacenter traffic, this platform investigates optical interconnection system concepts capable to support 16QAM 40GBd data traffic, exploiting the advancements of silicon and polymer technologies

Integrated photonic tunable basic units using dual-drive directional couplers

"© 2019 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"[EN] Photonic integrated circuits based on waveguide meshes and multibeam interferometers call for large-scale integration of Tunable Basic Units (TBUs) that feature beam splitters and waveguides. This units are loaded with phase actuators to provide complex linear processing functionalities based on optical interference and can be reconfigured dynamically. Here, we propose and experimentally demonstrate, to the best of our knowledge, for the first time, a thermally actuated Dual-Drive Directional Coupler (DD-DC) design integrated on a silicon nitride platform. It operates both as a standalone optical component providing arbitrary optical beam splitting and common phase as well as a low loss and potentially low footprint TBU. Finally, we report the experimental demonstration of the first integrated triangular waveguide mesh arrangement using DD-DC based TBUs and provide an extended analysis of its performance and scalability. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing AgreementEuropean Research Council (ERC ADG-2016UMWP-Chip, ERC-POC-2019 FPPAs); Generalitat Valenciana (PROMETEO 2017/017); European Cooperation in Science and Technology (COST Action CA16220 EUIMWP.).Pérez-López, D.; Gutierrez Campo, AM.; Sánchez-Gomáriz, E.; Dasmahapatra, P.; Capmany Francoy, J. (2019). Integrated photonic tunable basic units using dual-drive directional couplers. Optics Express. 27(26):38071-38086. https://doi.org/10.1364/OE.27.03807138071380862726Soref, R. (2006). The Past, Present, and Future of Silicon Photonics. IEEE Journal of Selected Topics in Quantum Electronics, 12(6), 1678-1687. doi:10.1109/jstqe.2006.883151Somekh, S., Garmire, E., Yariv, A., Garvin, H. L., & Hunsperger, R. G. (1974). Channel Optical Waveguides and Directional Couplers in GaAs–Imbedded and Ridged. Applied Optics, 13(2), 327. doi:10.1364/ao.13.000327Pérez, D., Gasulla, I., Capmany, J., & Soref, R. A. (2016). Reconfigurable lattice mesh designs for programmable photonic processors. Optics Express, 24(11), 12093. doi:10.1364/oe.24.012093Clements, W. R., Humphreys, P. C., Metcalf, B. J., Kolthammer, W. S., & Walsmley, I. A. (2016). Optimal design for universal multiport interferometers. Optica, 3(12), 1460. doi:10.1364/optica.3.001460Zhuang, L., Roeloffzen, C. G. H., Hoekman, M., Boller, K.-J., & Lowery, A. J. (2015). Programmable photonic signal processor chip for radiofrequency applications. Optica, 2(10), 854. doi:10.1364/optica.2.000854Pérez, D., Gasulla, I., Crudgington, L., Thomson, D. J., Khokhar, A. Z., Li, K., … Capmany, J. (2017). Multipurpose silicon photonics signal processor core. Nature Communications, 8(1). doi:10.1038/s41467-017-00714-1Perez-Lopez, D., Sanchez, E., & Capmany, J. (2018). Programmable True Time Delay Lines Using Integrated Waveguide Meshes. Journal of Lightwave Technology, 36(19), 4591-4601. doi:10.1109/jlt.2018.2831008Kogelnik, H., & Schmidt, R. (1976). Switched directional couplers with alternating ΔΒ. IEEE Journal of Quantum Electronics, 12(7), 396-401. doi:10.1109/jqe.1976.1069190Schmidt, R. V., & Kogelnik, H. (1976). Electro‐optically switched coupler with stepped Δβ reversal using Ti‐diffused LiNbO3waveguides. Applied Physics Letters, 28(9), 503-506. doi:10.1063/1.88833Alferness, R. C., & Veselka, J. J. (1985). Simultaneous modulation and wavelength multiplexing with a tunable Ti:LiNbO3directional coupler filter. Electronics Letters, 21(11), 466-467. doi:10.1049/el:19850330Sharkawy, A., Shi, S., Prather, D. W., & Soref, R. A. (2002). Electro-optical switching using coupled photonic crystal waveguides. Optics Express, 10(20), 1048. doi:10.1364/oe.10.001048Orlandi, P., Morichetti, F., Strain, M. J., Sorel, M., Melloni, A., & Bassi, P. (2013). Tunable silicon photonics directional coupler driven by a transverse temperature gradient. Optics Letters, 38(6), 863. doi:10.1364/ol.38.000863Pérez, D., & Capmany, J. (2019). Scalable analysis for arbitrary photonic integrated waveguide meshes. Optica, 6(1), 19. doi:10.1364/optica.6.000019Rios, C., Stegmaier, M., Cheng, Z., Youngblood, N., Wright, C. D., Pernice, W. H. P., & Bhaskaran, H. (2018). Controlled switching of phase-change materials by evanescent-field coupling in integrated photonics [Invited]. Optical Materials Express, 8(9), 2455. doi:10.1364/ome.8.002455Zheng, J., Khanolkar, A., Xu, P., Colburn, S., Deshmukh, S., Myers, J., … Majumdar, A. (2018). GST-on-silicon hybrid nanophotonic integrated circuits: a non-volatile quasi-continuously reprogrammable platform. Optical Materials Express, 8(6), 1551. doi:10.1364/ome.8.001551Capmany, J., Domenech, D., & Muñoz, P. (2014). Silicon graphene waveguide tunable broadband microwave photonics phase shifter. Optics Express, 22(7), 8094. doi:10.1364/oe.22.008094Abel, S., Eltes, F., Ortmann, J. E., Messner, A., Castera, P., Wagner, T., … Fompeyrine, J. (2018). Large Pockels effect in micro- and nanostructured barium titanate integrated on silicon. Nature Materials, 18(1), 42-47. doi:10.1038/s41563-018-0208-0Sanchez, L., Lechago, S., Gutierrez, A., & Sanchis, P. (2016). Analysis and Design Optimization of a Hybrid VO2/Silicon2 $\times$ 2 Microring Switch. IEEE Photonics Journal, 8(2), 1-9. doi:10.1109/jphot.2016.2551463Qiao, L., Tang, W., & Chu, T. (2017). 32 × 32 silicon electro-optic switch with built-in monitors and balanced-status units. Scientific Reports, 7(1). doi:10.1038/srep42306Zheng, D., Doménech, J. D., Pan, W., Zou, X., Yan, L., & Pérez, D. (2019). Low-loss broadband 5  ×  5 non-blocking Si3N4 optical switch matrix. Optics Letters, 44(11), 2629. doi:10.1364/ol.44.002629Capmany, J., Gasulla, I., & Pérez, D. (2015). The programmable processor. Nature Photonics, 10(1), 6-8. doi:10.1038/nphoton.2015.254Carolan, J., Harrold, C., Sparrow, C., Martín-López, E., Russell, N. J., Silverstone, J. W., … Laing, A. (2015). Universal linear optics. Science, 349(6249), 711-716. doi:10.1126/science.aab3642Lee, B. G., & Dupuis, N. (2019). Silicon Photonic Switch Fabrics: Technology and Architecture. Journal of Lightwave Technology, 37(1), 6-20. doi:10.1109/jlt.2018.2876828Seok, T. J., Quack, N., Han, S., Muller, R. S., & Wu, M. C. (2016). Large-scale broadband digital silicon photonic switches with vertical adiabatic couplers. Optica, 3(1), 64. doi:10.1364/optica.3.00006

Dynamics of High-Technology Firms in the Silicon Valley

The pace of technological innovation since World War II is dramatically accelerating following the commercial exploitation of the Internet. Since the mid 90’s fiber optics capacity (infrastructure for transmission of information including voice and data) has incremented over one hundred times thanks to a new technology, dense wave division multiplexing, and Internet traffic has increased over 1.000 times. The dramatic advances in information technology provide excellent examples of the critical relevance of the knowledge in the development of competitive advantages. The Silicon Valley (SV) that about fifty years ago was an agricultural region became the center of dramatic technological and organizational transformations. In fact, most of the present high-tech companies did not exist twenty years ago. Venture capital contribution to the local economy is quite important not only due to the magnitude of the financial investment (venture investment in SV during 2000 surpassed 25.000 millions of dollars) but also because the extent and quality of networks (management teams, senior employees, customers, providers, etc.) that bring to emerging companies. How do new technologies develop? What is the role of private and public investment in the financing of R&D? Which are the most dynamical agents and how do they interact? How are new companies created and how do they evolve? The discussion of these questions is the focus of the current work.Technological development, R&D, networks

Physics of the Cosmos (PCOS) Program Technology Development 2018

We present a final report on our program to raise the Technology Readiness Level (TRL) of enhanced chargecoupleddevice (CCD) detectors capable of meeting the requirements of Xray grating spectrometers (XGS) and widefield Xray imaging instruments for small, medium, and large missions. Because they are made of silicon, all Xray CCDs require blocking filters to prevent corruption of the Xray signal by outofband, mainly optical and nearinfrared (nearIR) radiation. Our primary objective is to demonstrate technology that can replace the fragile, extremely thin, freestanding blocking filter that has been standard practice with a much more robust filter deposited directly on the detector surface. Highperformance, backilluminated CCDs have flown with freestanding filters (e.g., one of our detectors on Suzaku), and other relatively lowperformance CCDs with directly deposited filters have flown (e.g., on the Xray Multimirror MissionNewton, XMMNewton Reflection Grating Spectrometer, RGS). At the inception of our program, a highperformance, backilluminated CCD with a directly deposited filter has not been demonstrated. Our effort will be the first to show such a filter can be deposited on an Xray CCD that meets the requirements of a variety of contemplated future instruments. Our principal results are as follows: i) we have demonstrated a process for direct deposition of aluminum optical blocking filters on backilluminated MIT Lincoln Laboratory CCDs. Filters ranging in thickness from 70 nm to 220 nm exhibit expected bulk visibleband and Xray transmission properties except in a small number (affecting 1% of detector area) of isolated detector pixels ("pinholes"), which show higherthanexpected visibleband transmission; ii) these filters produce no measurable degradation in softXray spectral resolution, demonstrating that direct filter deposition is compatible with the MIT Lincoln Laboratory backillumination process; iii) we have shown that under sufficiently intense visible and nearIR illumination, outofband light can enter the detector through its sidewalls and mounting surfaces, compromising detector performance. This 'sidewall leakage' has been observed, for example, by a previous experiment on the International Space Station during its orbitday operations. We have developed effective countermeasures for this sidewall leakage; iv) we developed an exceptionally productive collaboration with the Regolith Xray Imaging Spectrometer (REXIS) team. REXIS is a student instrument now flying on the Origins Spectral Interpretation Resource Identification Security - Regolith Explorer (OSIRISREx) mission. REXIS students participated in our filter development program, adopted our technology for their flight instrument, and raised the TRL of this technology beyond our initial goals. This Strategic Astrophysics Technology (SAT) project, a collaboration between the MKI and MIT Lincoln Laboratory, began July 1, 2012, and ended on June 30, 2018

Program Annual Technology Report: Physics of the Cosmos Program Office

From ancient times, humans have looked up at the night sky and wondered: Are we alone? How did the universe come to be? How does the universe work? PCOS focuses on that last question. Scientists investigating this broad theme use the universe as their laboratory, investigating its fundamental laws and properties. They test Einsteins General Theory of Relativity to see if our current understanding of space-time is borne out by observations. They examine the behavior of the most extreme environments supermassive black holes, active galactic nuclei, and others and the farthest reaches of the universe, to expand our understanding. With instruments sensitive across the spectrum, from radio, through infrared (IR), visible light, ultraviolet (UV), to X rays and gamma rays, as well as gravitational waves (GWs), they peer across billions of light-years, observing echoes of events that occurred instants after the Big Bang. Last year, the LISA Pathfinder (LPF) mission exceeded expectations in proving the maturity of technologies needed for the Laser Interferometer Space Antenna (LISA) mission, and the Laser Interferometer Gravitational-Wave Observatory (LIGO) recorded the first direct measurements of long-theorized GWs. Another surprising recent discovery is that the universe is expanding at an ever-accelerating rate, the first hint of so-called dark energy, estimated to account for 75% of mass-energy in the universe. Dark matter, so called because we can only observe its effects on regular matter, is thought to account for another20%, leaving only 5% for regular matter and energy. Scientists now also search for special polarization in the cosmic microwave background to support the notion that in the split-second after the Big Bang, the universe inflated faster than the speed of light! The most exciting aspect of this grand enterprise today is the extraordinary rate at which we can harness technologies to enable these key discoveries

Modelling of a lens antenna receiver system for NASA GUSTO

The radiation at terahertz (THz) frequency range (1 THz = 300 μm in wavelength) provides us a powerful window into cosmic evolution, from the birth and explosion of stars to the evolution of galaxies and the universe itself. The THz is a largely unexplored region in the electro-magnetic spectrum, partly owing to technological constraints and partly due to atmospheric absorption on the Earth. Consequently, THz astronomy observations are best performed from space-based or balloon-borne telescopes, like the proposed NASA balloon GUSTO mission. The observations will be complementary to other space missions like Hershel’s HIFI instrument. In this work, a model of GUSTO’s optical system was proposed and analysed in order to improve its efficiency in detecting three of the most important terahertz lines, [NII], [CII] and [OI], with multi-pixel heterodyne cameras. Moreover, simulations were performed with PILRAP, a antenna simulation software, to study the parameters that affect the optical f# number and radiation pattern of a 5 mm diameter lens system, and to explain the heterodyne sensitivity differences between a 10 mm lens and 3.1 mm lenses. Outcome of my thesis work concludes the feasibility to use smaller lens for GUSTO’s heterodyne arrays

Science Mission Directorate TechPort Records for 2019 STI-DAA Release

The role of the Science Mission Directorate (SMD) is to enable NASA to achieve its science goals in the context of the Nation's science agenda. SMD's strategic decisions regarding future missions and scientific pursuits are guided by Agency goals, input from the science community including the recommendations set forth in the National Research Council (NRC) decadal surveys and a commitment to preserve a balanced program across the major science disciplines. Toward this end, each of the four SMD science divisions -- Heliophysics, Earth Science, Planetary Science, and Astrophysics -- develops fundamental science questions upon which to base future research and mission programs

Space QUEST mission proposal: experimentally testing decoherence due to gravity

Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum correlations, such as entanglement, may exhibit different behavior to purely classical correlations in curved space. By measuring this effect or lack thereof, we can test the hypotheses behind several such models. For instance, as predicted by Ralph et al [5] and Ralph and Pienaar [1], a bipartite entangled system could decohere if each particle traversed through a different gravitational field gradient. We propose to study this effect in a ground to space uplink scenario. We extend the above theoretical predictions of Ralph and coworkers and discuss the scientific consequences of detecting/failing to detect the predicted gravitational decoherence. We present a detailed mission design of the European Space Agency's Space QUEST (Space—Quantum Entanglement Space Test) mission, and study the feasibility of the mission scheme.Peer ReviewedPostprint (published version