Silicon slow-light-based photonic mixer for microwave-frequencyconversion applications

This paper was published in OPTICS LETTERS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.37.001721. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] We describe and demonstrate experimentally a method for photonic mixing of microwave signals by using a silicon electro-optical Mach¿Zehnder modulator enhanced via slow-light propagation. Slow light with a group index of ~11, achieved in a one-dimensional periodic structure, is exploited to improve the upconversion performance of an input frequency signal from 1 to 10.25 GHz. A minimum transmission point is used to successfully demonstrate the upconversion with very low conversion losses of ~7¿¿dB and excellent quality of the received I/Q modulated QPSK signal with an optimum EVM of ~8%.Financial support from FP7-224312 HELIOS project and Generalitat Valenciana under PROMETEO-2010-087 R&D Excellency Program (NANOMET) are acknowledged. F. Y.Gardes, D. J. Thomson, and G. T. Reed are supported by funding received from the UK EPSRC funding body under the grant “UK Silicon Photonics.” The author A. M. Gutiérrez thanks D. Marpaung for his useful help.Gutiérrez Campo, AM.; Brimont, ACJ.; Herrera Llorente, J.; Aamer, M.; Martí Sendra, J.; Thomson, DJ.; Gardes, FY.... (2012). Silicon slow-light-based photonic mixer for microwave-frequencyconversion applications. Optics Letters. 37(10):1721-1723. https://doi.org/10.1364/OL.37.001721S17211723371

Refractive indices of MBE-grown AlxGa(1−x)As ternary alloys in the transparent wavelength region

A series of AlxGa(1−x)As ternary alloys were grown by molecular beam epitaxy (MBE) at the technologically relevant composition range, x < 0.45, and characterized using spectroscopic ellipsometry to provide accurate refractive index values in the wavelength region below the bandgap. Particular attention is given to O-band and C-band telecommunication wavelengths around 1.3 µm and 1.55 µm, as well as at 825 nm. MBE gave a very high accuracy for grown layer thicknesses, and the alloys’ precise compositions and bandgap values were confirmed using high-resolution x-ray diffraction and photoluminescence, to improve the refractive index model fitting accuracy. This work is the first systematic study for MBE-grown AlxGa(1−x)As across a wide spectral range. In addition, we employed a very rigorous measurement-fitting procedure, which we present in detail

Optical fiber-to-chip assembly process for ultra-low loss photonic devices based on silicon nitride for space applications

[EN] In this work, we demonstrate an efficient fiber array-to-chip assembly process with a high number of input/output ports. The proposed approach is based on using a pre-alignment coupling structure to separately align the input and output ports. The assembling process has been experimentally validated in photonic integrated circuits fabricated with an ultra-low-loss waveguide technology based on silicon nitride, which features propagation losses as low as 9.5 dB/m. The developed technology is expected to extend the use of integrated photonics for space applicationsThis work was supported by EU-funded H2020 project RETINA under grant agreement n° 821943Brimont, ACJ.; Zurita Herranz, D.; Duarte, VC.; Mengual, T.; Chmielak, B.; Suckow, S.; Giesecke, A.... (2020). Optical fiber-to-chip assembly process for ultra-low loss photonic devices based on silicon nitride for space applications. 1-3. http://hdl.handle.net/10251/1786581

Stakeholder perceptions of policy tools in support of sustainable food consumption in Europe: Policy implications

Transitioning agri-food systems towards increased sustainability and resilience requires that attention be paid to sustainable food consumption policies. Policy-making processes often require the engagement and acceptance of key stakeholders. This study analyses stakeholders' solutions for creating sustainable agri-food systems, through interviews with a broad range of stakeholders including food value chain actors, non-governmental organizations, governmental institutions, research institutions and academic experts. The study draws on 38 in-depth, semi-structured interviews conducted in four European countries: France, Iceland, Italy and the UK, as well as three interviews with high-level EU experts. The interviewees' solutions were analysed according to a five-category typology of policy tools, encompassing direct activity regulations, and market-based, knowledge-based, governance and strategic policy tools. Most of the identified solutions were located in the strategic tools category, reflecting shared recognition of the need to integrate food policy to achieve long-term goals. Emerging solutions-those which were most commonly identified among the different national contexts-were then used to derive empirically-grounded and more universally applicable recommendations for the advancement of sustainable food consumption policies

Silicon CMOS photonics platform for enabling high-speed DQPSK transceivers

In this work we review the results obtained under the framework of FP7-HELIOS project for integrated DQPSK transceivers in silicon photonics. A differential DQPSK receiver with balanced zero biased Germanium photodiodes has been demonstrated at 10Gbit/s with an error floor around 10(-15). Furthermore, DPSK modulation up to 10Gbit/s with a bit error rate below 10(-9) is also demonstrated using a silicon push-pull operated dual-drive Mach-Zehnder modulator (MZM) based on carrier depletion. The results indicate the potential of the silicon CMOS photonics platform for boosting next-generation optical networks based on advanced modulation formats

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

Silicon optical modulators for high data rate applications

Abstract In this work we describe the carrier depletion MZI modulators, slow wave structures for modulation enhancement and the QCSE modulator which are under development in the European HELIOS project and the UK Silicon Photonics project. Introduction High performance silicon optical modulators are key to many silicon based photonic applications. Over the previous decade the development seen in the performance of silicon optical modulators has been vast. Several routes to modulation have been used to overcome the lack of a strong electro optic effect in silicon. These include the plasma dispersion effect, III-V hybrid device fabrication, SiGe devices, Polymer and Strain induced electro-optic effects. Reported performances now regularly range from 10Gbit/s up to 40Gbit/s. HELIOS, which is a European FP7 funded project and the UK silicon photonics project (UKSP), funded by the EPSRC both involve the development of the different photonic components required to form photonic circuits with a range of functionality. Within both projects there is strong modulator activity with carrier depletion based modulation, QCSE modulation and structures to gain enhancement of the modulation effect under development. Carrier depletion modulation Optical modulators based upon free carrier depletion are widely regarded as being the simplest approach to achieve high performance modulation in silicon. They operate by reverse biasing a diode structure which is incorporated in or around an optical waveguide. The depletion of free carriers therefore interacts with the propagating light causing a change in phase through the plasma dispersion effect. Within the HELIOS project two phase modulators based upon this approach are under investigation using both PN and PIPIN diodes. Cross sectional diagrams of these devices are shown in figure 1. The first structure is based in silicon-on-insulator (SOI) of 220nm thickness. The waveguide section and the slab to one side is doped p type. The slab on the other side of the waveguide is then doped n type setting up a pn junction at the edge of the waveguide rib. The concentration of the n type doping is made larger than the p type doping such that the depletion region extends mainly into the waveguide during reverse bias. These lightly doped p and n type regions extend out to meet highly doped regions which in turn provide ohmic contacts to coplanar waveguide electrodes which are used to drive the device. The devic

Silicon optical modulators

Optical technology is poised to revolutionize short-reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such an interconnect is the optical modulator. Modulators have been improved dramatically in recent years, with a notable increase in bandwidth from the megahertz to the multigigahertz regime in just over half a decade. However, the demands of optical interconnects are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimizing metrics such as the device footprint and energy requirement per bit, while also maximizing bandwidth and modulation depth, is non-trivial. All of this must be achieved within an acceptable thermal tolerance and optical spectral width using CMOS-compatible fabrication processes. This Review discusses the techniques that have been (and will continue to be) used to implement silicon optical modulators, as well as providing an outlook for these devices and the candidate solutions of the future