Towards micro-assembly of hybrid MOEMS components on reconfigurable silicon free-space micro-optical bench.

International audienceThe 3D integration of hybrid chips is a viable approach for the micro-optical technologies to reduce the costs of assembly and packaging. In this paper a technology platform for the hybrid integration of MOEMS components on a reconfigurable free-space silicon micro-optical bench is presented. In this approach a desired optical component (e.g. micromirror, microlens) is integrated with removable and adjustable silicon holder which can be manipulated, aligned and fixed in the precisely etched rail of the silicon baseplate by use of robotic micro-assembly station. An active-based gripping system allows modification of the holder position on the baseplate with nanometre precision. The fabrication processes of the micromachined parts of the micro-optical bench, based on bulk micromachining of standard silicon wafer and SOI wafer, are described. The successful assembly of the holders, equipped with micromirror and refractive glass ball microlens, on the baseplate rail is demonstrated

Addressing Fiber-to-Chip Coupling Issues in Silicon Photonics

Esta tesis trata de resolver el problema de la interconexión (acoplo) entre un circuito integrado fotónico de silicio (chip) y el mundo exterior, es decir una fibra óptica. Se trata de uno de los temas más importantes a los que hoy en día se enfrenta la comunidad científica en óptica integrada de silicio. A pesar de que pueden realizarse circuitos integrados fotónicos de silicio de muy alta calidad utilizando herramientas estándar de fabricación CMOS, la interfaz con la fibra óptica sigue siendo la fuente más importante de pérdidas, debido a la gran diferencia en el tamaño entre los modos de propagación de la fibra y de las guías de los circuitos integrados fotónicos. Abordar el problema es, por lo tanto, muy importante para poder utilizar los circuitos integrados fotónicos de silicio en una aplicación práctica. Objetivos: El propósito de este trabajo es hacer frente a este problema en la interfaz del acoplamiento fibra-chip, con énfasis en el ensamblado o empaquetado final. Por lo tanto, los objetivos principales son: 1) estudio, modelado y optimización de diseños de diferentes técnicas eficientes de acoplamiento entre fibras ópticas y circuitos integrados fotónicos de silicio, 2) fabricación y demostración experimental de los diseños obtenidos, 3) ensamblado y empaquetado de algunos de los prototipos de acoplamiento fabricados. Metodología: Este trabajo se desarrolla a lo largo de dos líneas de investigación, en conformidad con las dos principales estrategias de acoplamiento que pueden encontrarse en la literatura, concretamente, estructuras de acoplamiento tipo "grating" (la fibra acopla verticalmente sobre la superficie de circuito), y estructuras del tipo ¿inverted taper¿ (la fibra acopla horizontalmente por el extremo de circuito). Resultados: tanto en el caso de estructuras tipo "grating" como en el caso de estructuras "inverted taper", son importantes los avances conseguidos sobre el estado del arte. En lo que respecta al "grating", se ha demostrado dos tipos de estructuras. Por un lado, se ha demostrado "gratings" adecuados para acoplo a guías de silicio convencionales. Por otra parte, se ha demostrado por primera vez el funcionamiento de "gratings" para guías de silicio tipo "slot" horizontal, que son un tipo de guía muy prometedora para aplicaciones de óptica no lineal. En relación con el acoplamiento a través de "inverted taper", se ha demostrado una estructura novedosa basada en este tipo de acoplamiento. Con esta estructura, importantes son los avances conseguidos en el empaquetado de fibras ópticas con el circuito de silicio. Su innovadora integración con estructuras de tipo "V-groove" se presenta como un medio para alinear pasivamente conjuntos de múltiples fibras a un mismo circuito integrado fotónico. También, se estudia el empaquetado de conjuntos de múltiples fibras usando acopladores tipo "grating", resultando en un prototipo de empaquetado de reducido tamaño.Galán Conejos, JV. (2010). Addressing Fiber-to-Chip Coupling Issues in Silicon Photonics [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/9196Palanci

Design and Development of an Optical Chip Interferometer For High Precision On-Line Surface Measurement

Advances in manufacturing and with the demand of achieving faster throughput at a lower cost in any industrial setting have put forward the need for embedded metrology. Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the workpiece. Providing closer integration of metrology upon the manufacturing platform will improve material processing and reliability of manufacture for high added value products in ultra-high-precision engineering. Currently, almost all available metrology instrumentation is either too bulky, slow, destructive in terms of damaging the surfaces with a contacting stylus or is carried out off-line. One technology that holds promise for improving the current state-of-the-art in the online measurement of surfaces is hybrid photonic integration. This technique provides for the integration of individual optoelectronic components onto silicon daughter boards which are then incorporated on a silica motherboard containing waveguides to produce a complete photonic circuit. This thesis presents first of its kind a novel chip interferometer sensor based on hybrid integration technology for online surface and dimensional metrology applications. The complete metrology sensor system is structured into two parts; hybrid photonic chip and optical probe. The hybrid photonic chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. Optical probe is a separate entity attached to the integrated optic module which serves as optical stylus for surface scanning in two measurement modes a) A single-point for measuring distance and thus form/surface topography through movement of the device or workpiece, b) Profiling (lateral scanning where assessment of 2D surface parameters may be determined in a single shot. Wavelength scanning and phase shifting inteferometry implemented for the retrival of phase information eventually providing the surface height measurement. The signal analysis methodology for the two measurement modes is described as well as a theoretical and experimental appraisal of the metrology capabilities in terms of range and resolution. The incremetal development of various hybrid photonic modules such as wavelength encoder unit, signal detection unit etc. of the chip interferometer are presented. Initial measurement results from various componets of metrology sensor and the surface measurement results in two measurement modes validate the applicability of the described sensor system as a potential metrology tool for online surface measurement applications

Optimized grating coupler designs for integrated photonics

A wide range of expertise is enclosed in the expression: “Photonics Packaging” with the common aim of interfacing a Photonic Integrated Circuit (PIC), either optically, electrically, thermally, and mechanically, with the surrounding environment. Thus, a multi-physics approach is essential to tackle the many challenges that Photonics Packaging poses. In this context, the design process is a crucial and vital step to overcome the majority of the issues that can potentially arise during the packaging assembly procedure. As a consequence, a single person cannot manage all the aspects behind the design process, but a multidisciplinary team needs to work together engineering and optimizing the different types of connections. The current thesis work is oriented on the optical packaging branch with particular focus on the design of the optical connections needed to deliver, in an efficiently and controlled manner, the light signal from a specific external light source or waveguide into the PIC. This work aims to show the importance of the design process in photonics packaging, and how it can be carefully exploited and tailored to optimize coupling schemes to obtain high efficient and packaging compatible optical connectors, which can constitute the building-blocks of future photonic devises. In this context, my research deals with the optimization of complex grating couplers for SOI platforms to couple light from a specific coupling scheme and it is divided in 4 sections. First, Chapter 2 presents in details the customized design routine, developed during my PhD, based on a Particle Swarm Optimization, an iterative algorithm, implemented using a commercial Finite Different Time Domain (FDTD) software. Then, in Chapter 3, the routine is exploited and tested to optimize the structural features of non-uniform grating coupler designs, characterized by a non-constant pitch. The aim is boosting their Coupling-Efficiency (CE) under a horizontal fibre coupling scheme, which is of particular interest in photonics packaging. The optimal designs were then fabricated in Cornerstone, the Silicon photonics foundry of the University of Southampton, and eventually packaged and tested at Tyndall National Institute. High CE values, up to 83% at 1550nm, are demonstrated and the results are shown to be in excellent agreement with the computational predictions. Due to the high efficiency, these designs were requested by the foundry as part of their official Process Design Kit, which is now on offer. In Chapter 4, the first experimental and FDTD comparative analysis of the multiwavelength response, in terms of bandwidth and asymmetry of the CE curve, is conducted and reported for such optimized non-uniform grating couplers. Here, the bandwidth is shown to be inversely proportional to the dimension of the impinging mode field diameter, which affects, together with the energy dispersion curve of each grating structure, its CE curve. Grating coupling is not only a suitable packaging solution for fiber-to-PIC coupling, but also for direct laser-to-PIC coupling. Chapter 5 shows how millimetre-scale FDTD simulations can be used to carefully design a Micro Optical Bench, made of a micro ball-lens and a micro prism. The Optics are used to reshape the laser emission making it compatible with a single mode fiber emission, thus suitable for grating coupling. Here, a uniform grating coupler is used to couple the impinging electromagnetic field. A laser-to-PIC performance penalty of only 1dB, with respect to the fiber-to-PIC coupling scheme, is shown under perfect alignment conditions. The origin of the higher loss is carefully analysed suggesting that 0.6dB are due to back-reflection from the optics interfaces, and 0.4dB due to spherical aberrations. Moreover, a detailed analysis of the manufacturing and alignment tolerances is conducted demonstrating their compatibility with current standard packaging processes

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

Next Generation Silicon Photonic Transceiver: From Device Innovation to System Analysis

Silicon photonics is recognized as a disruptive technology that has the potential to reshape many application areas, for example, data center communication, telecommunications, high-performance computing, and sensing. The key capability that silicon photonics offers is to leverage CMOS-style design, fabrication, and test infrastructure to build compact, energy-efficient, and high-performance integrated photonic systems-on- chip at low cost. As the need to squeeze more data into a given bandwidth and a given footprint increases, silicon photonics becomes more and more promising. This work develops and demonstrates novel devices, methodologies, and architectures to resolve the challenges facing the next-generation silicon photonic transceivers. The first part of this thesis focuses on the topology optimization of passive silicon photonic devices. Specifically, a novel device optimization methodology - particle swarm optimization in conjunction with 3D finite-difference time-domain (FDTD), has been proposed and proven to be an effective way to design a wide range of passive silicon photonic devices. We demonstrate a polarization rotator and a 90◦ optical hybrid for polarization-diversity and phase-diversity communications - two important schemes to increase the communication capacity by increasing the spectral efficiency. The second part of this thesis focuses on the design and characterization of the next- generation silicon photonic transceivers. We demonstrate a polarization-insensitive WDM receiver with an aggregate data rate of 160 Gb/s. This receiver adopts a novel architecture which effectively reduces the polarization-dependent loss. In addition, we demonstrate a III-V/silicon hybrid external cavity laser with a tuning range larger than 60 nm in the C-band on a silicon-on-insulator platform. A III-V semiconductor gain chip is hybridized into the silicon chip by edge-coupling to the silicon chip. The demonstrated packaging method requires only passive alignment and is thus suitable for high-volume production. We also demonstrate all silicon-photonics-based transmission of 34 Gbaud (272 Gb/s) dual-polarization 16-QAM using our integrated laser and silicon photonic coherent transceiver. The results show no additional penalty compared to commercially available narrow linewidth tunable lasers. The last part of this thesis focuses on the chip-scale optical interconnect and presents two different types of reconfigurable memory interconnects for multi-core many-memory computing systems. These reconfigurable interconnects can effectively alleviate the memory access issues, such as non-uniform memory access, and Network-on-Chip (NoC) hot-spots that plague the many-memory computing systems by dynamically directing the available memory bandwidth to the required memory interface

InP microdisks for optical signal processing and data transmission

The performance increase in telecommunication and computing systems demands an ever increasing input-output (IO) bandwidth and IO density, which can be met by integrated photonics. Using photonic integration, much higher densities of optical components can be achieved allowing for short-range optical communication systems in, e.g., high performance computers. The key functionalities required for these optical communication systems are light generation, light modulation and light detection. In addition to this other functionalities are also desirable, such as wavelength conversion. This thesis highlights the design and fabrication of indium phosphide (InP) microdisks heterogeneously integrated on silicon-on-insulator substrates. The fabrication of the microdisks in a laboratory clean-room environment is described. These devices can fulfil the above-mentioned functions required in optical communication. Experiments are then performed on the fabricated devices dealing with these various functionalities that are required for optical communication. The lasing properties of the devices are shown and simulated with a spatiallydependent rate equation model accurately predicting the device behaviour. A detailed speed analysis is given, including a parameter extraction of the devices. The operation of the devices as detectors is highlighted. Furthermore the PhD thesis provides a deep analysis of the use of InP microdisks as modulators. Besides the forward-biased operation principle using the free-carrier plasma-dispersion effect, also a high-speed reversely biased operation mode is proposed and demonstrated experimentally. The thesis also describes various approaches on how to improve the performance of the devices, in particular when using them as lasers. Ways how to increase the output power and how to enhance the operation speed are discussed. Because the device is strongly dependent on the coupling between the resonant InP cavity and the silicon waveguide, an extensive analysis of the coupling and the influence of certain process steps on the device performance are given. The PhD thesis concludes the work carried out on InP microdisks and gives an outlook about improving the device performance with respect to specific applications and how to further improve the manufacturability of the devices. Finally, for the InP microdisk-based devices an outlook is given about suitable applications, such as on-chip optical links for instance

Scalable designs and methods for heterogeneous electronic-photonic integrated circuitry

A set of semiconductor designs shown to be capable of facilitating scalable and reconfigurable layouts for electronic-photonic integrated circuitry is presented. Three emphases are established to outline and discuss the methods and advantages of merging stand-alone optical components into integrated heterogeneous systems, specifically for implementing optical sensing, efficient laser wavelength tuning, and III-V-on-Si semiconductor fabrication techniques together on a single platform. Considerations regarding the optical geometries and power efficiency of each design are reiterated to assure that each design is compatible with the goals of system-level integration in either biochemical point-of-use or telecommunications applications. These three approaches to scalable photonic designs are then investigated in their ability to offer dynamic controls of optical signals and their novel usage of heterogeneous material patterning. The optical sensing platform directly integrates multiple linear variable filters (LVFs) atop a CMOS image sensor for electronic controls of detecting a biochemical fluorescent or absorptive optical signal signature, enabling good wavelength resolution (3.77−6.08 nm) over a wide-band detection spectrum. Detection limits of 0.28 nM for Quantum Dot emitters and 32 ng/mL for near-infrared fluorescent dyes are found in this integrated design, providing comparable results in the compact optical platform to conventional laboratory spectrometers. The instrument is then extended in its usage by testing on point-of-use detection tests via discerning the concentration of free-chlorine in water colorimetrically. The tunable laser cavity design integrates together a GaN waveguide into a standard InGaAsP telecom (1550 nm) edge-emitting laser atop silicon, allowing for wide-band tuning via the strong anisotropic effects solved for in wurtzite GaN. A tuning parameter based off a refractive index variation, Δ, is found to be at |1.75∙10E−4|, based off the electro-optic effects in conjunction with an etched grating geometry designed directly into the coupled GaN waveguide, with the structure further extended into a Y-branch laser cavity to enable the Vernier effect for wideband tuning via mode-hopping. A separate GaN-based design, consisting of an RF signal modulator that launches a surface acoustic wave (SAW) into a cavity to produce a highly controllable refractive index variation, Δ, via the photo-elastic and photo-elastic effects, is found to produce a large tuning parameter of |1.84∙10E−3|. These effects are then described in their application to dynamically controllable effects for dense wavelength division multiplexing (DWDM) and how the underlying electronic platform enables this, providing advantages over larger footprint or less efficient designs. The fabrication techniques designed provide a method to enable bonding of III-V epitaxial wafers onto a silicon carrier wafer for large-scale processing before final bonding onto CMOS. A processing recipe takes bulk GaAs epitaxial structures and constructs a method for reversibly bonding and processing them on a silicon carrier wafer as III-V islands, ready for final large scale flip-chip bonding onto aligning CMOS features. Additional findings discuss the merits of various etch processes and techniques such that they are compatible to the heterogeneous III-V-on-Si patterning as laid out. The methods optimized allow for simultaneous, heterogeneous development of system-level device integration such that further processing can place various III-V devices side-by-side and process geometries in unison. Processing steps and their results are presented. The extension of this method to different III-V alloys beyond GaAs entirely is therefore considered for even larger-scale system design across photonic elements. Each set of findings presents both the relevant photonic device characteristics and also a method on how to intersect these devices with a paired CMOS electronic system on silicon, so that a single unified electronic-photonic schematic can be made. Accompanying these conclusions is a range of experimental work ranging from simulation studies, to full-scale integrable sensing designs and their testing, to detailed cleanroom-based fabrication processes for designing the system of III-V-on-Si patterns. A final set of conclusions relates the three tracks of research as being part of a common path forward in scalable photonics designs. Forecasts are then made on how the field of electronic-photonic integration and its applications utilized herein may yet evolve and potentially encompass findings or methodologies from this work

Roadmap for optofluidics

Optofluidics, nominally the research area where optics and fluidics merge, is a relatively new research field and it is only in the last decade that there has been a large increase in the number of optofluidic. applications, as well as in the number of research groups, devoted to the topic. Nowadays optofluidics applications include, without being limited to, lab-on-a-chip devices, fluid-based and controlled lenses, optical sensors for fluids and for suspended particles, biosensors, imaging tools, etc. The long list of potential optofluidics applications, which have been recently demonstrated, suggests that optofluidic technologies will become more and more common in everyday life in the future, causing a significant impact on many aspects of our society. A characteristic of this research field, deriving from both its interdisciplinary origin and applications, is that in order to develop suitable solutions a. combination of a deep knowledge in different fields, ranging from materials science to photonics, from microfluidics to molecular biology and biophysics,. is often required. As a direct consequence, also being able to understand the long-term evolution of optofluidics research is not. easy. In this article, we report several expert contributions on different topics. so as to provide guidance for young scientists. At the same time, we hope that this document will also prove useful for funding institutions and stakeholders. to better understand the perspectives and opportunities offered by this research field

Lab-on-a-Chip Fabrication and Application

The necessity of on-site, fast, sensitive, and cheap complex laboratory analysis, associated with the advances in the microfabrication technologies and the microfluidics, made it possible for the creation of the innovative device lab-on-a-chip (LOC), by which we would be able to scale a single or multiple laboratory processes down to a chip format. The present book is dedicated to the LOC devices from two points of view: LOC fabrication and LOC application