Multimode optical waveguides and lightguides for backplane interconnection and laser illuminated display systems

The aim of the research in this thesis was to design, model, analyse and experimentally test multimode optical waveguides and lightguides for manipulating infrared light for optical backplane interconnections and visible light for laser illuminated display systems. Optical Input/Output Coupling loss at the entry and exit of polymer waveguides depends on optical scattering due to end facet roughness. The input/output coupling loss was measured for different end facet roughness magnitudes and the waveguide surface profiles due to different cutting methods (dicing saw and three milling routers) were compared. The effect of the number of cutting edges on the router, the rotation rate and translation (cutting) speed of the milling routers on the waveguide end facet roughness was established. A further new method for reducing the end facet roughness and so the coupling loss, by curing a layer of core material at the end of the waveguide to cover the roughness fluctuations, was proposed and successfully demonstrated giving the best results reported to date resulting in an improvement of 2.8 dB, even better than those obtained by use of index matching fluid which is impractical in commercial systems. The insertion loss due to waveguide crossing having various crossing angles was calculated using a beam propagation method and ray tracing simulations and compared to experimental measurements. Differences between the results were resolved leading to an understanding that only low order waveguide modes at no more than 6 degrees to the axis were propagating inside the waveguide. Several different optical designs of multimode waveguide for the light engine of a 3D autostereoscopic laser illuminated display system were proposed. Each design performed the functions of laser beam combining, beam shaping and beam homogenizing and the best method was selected, designed, modelled, tested, and implemented in the system. The waveguide material was inspected using spectroscopy to establish the effect of high power optical density on the material performance showing an increased loss particularly in the shorter wavelengths. The effect of waveguide dimensions on the speckle pattern was investigated experimentally and the speckle contrast was reduced to below the threshold of human perception. Speckle contrast was also recorded for the first time along the axis of the 3D display system and normal to it in the viewing area and the speckle characteristics at each stage were investigated. New algorithms for analysing speckle were used and the perceptual ability of human eyes to detect speckle size and contrast were taken into account to minimise perceived speckle patterns. The effect of the core diameter of optical fibres on the speckle pattern was investigated and it was shown that the speckle spot diameter is reduced by increasing the fibre core diameter. Based on this experiment, it was suggested that speckle reduction is more effective if the optical fibre used in the display system has larger diameter. Therefore, a slab waveguide of 1 mm thickness and 20 m width was used for laser beam combining, homogenising and beam shaping and a uniformity of 84% was achieved with just 75 mm length. The speckle was also completely removed at the output of the waveguid

Design, measurement and analysis of multimode light guides and waveguides for display systems and optical backplane interconnections

The aim of the research in this thesis was to design and model multimode lightguides for optimising visible light for liquid crystal display systems and to design, model and experimentally test infrared light propagation within polymer multimode waveguides as board-to-board interconnects for high data rate communication. Ray tracing models the behaviour of a novel LCD colour separating backlight to optimize its efficiency by establishing the optimum dimensions and position for a unique micro-mirror array within the light guide. The output efficiency increased by 38.2% compared to the case without the embedded mirror array. A novel simulation technique combined a model of liquid crystal director orientation and a non-sequential ray tracing program was used first time to compute the reflected intensity from a LCOS device for a rear projection TV system. The performance of the LCOS display was characterised by computing the contrast ratio over a ±15° viewing cone. Photolithographically manufactured embedded multimode waveguides made from acrylate Truemode® polymer are characterized by measuring the optical transmission loss of key waveguide components including. straight, bend and crossing. Design rules derived from the experimental measurement were used to optimize optical PCB (OPCB) layout. A most compact and complex optical interconnects layout up-to-date for data centres, including parallel straight waveguide sections, cascaded 90° bends and waveguide crossing other than 90° angles, was designed, tested and used in an optic-electrical demonstration platform to convey a 10.3 Gb/s data. A further new method for reducing the end facet roughness and so the coupling loss, by curing a thin layer of core material at the end of the waveguide facet to cover the roughness fluctuations, was proposed and successfully demonstrated giving the best results reported to date resulting in an improvement of 2.8 dB which was better than the results obtained by using index matching fluid

Architecture and Advanced Electronics Pathways Toward Highly Adaptive Energy- Efficient Computing

With the explosion of the number of compute nodes, the bottleneck of future computing systems lies in the network architecture connecting the nodes. Addressing the bottleneck requires replacing current backplane-based network topologies. We propose to revolutionize computing electronics by realizing embedded optical waveguides for onboard networking and wireless chip-to-chip links at 200-GHz carrier frequency connecting neighboring boards in a rack. The control of novel rate-adaptive optical and mm-wave transceivers needs tight interlinking with the system software for runtime resource management

Design automation and analysis of three-dimensional integrated circuits

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 165-176).This dissertation concerns the design of circuits and systems for an emerging technology known as three-dimensional integration. By stacking individual components, dice, or whole wafers using a high-density electromechanical interconnect, three-dimensional integration can achieve scalability and performance exceeding that of conventional fabrication technologies. There are two main contributions of this thesis. The first is a computer-aided design flow for the digital components of a three-dimensional integrated circuit (3-D IC). This flow primarily consists of two software tools: PR3D, a placement and routing tool for custom 3-D ICs based on standard cells, and 3-D Magic, a tool for designing, editing, and testing physical layout characteristics of 3-D ICs. The second contribution of this thesis is a performance analysis of the digital components of 3-D ICs. We use the above tools to determine the extent to which 3-D integration can improve timing, energy, and thermal performance. In doing so, we verify the estimates of stochastic computational models for 3-D IC interconnects and find that the models predict the optimal 3-D wire length to within 20% accuracy. We expand upon this analysis by examining how 3-D technology factors affect the optimal wire length that can be obtained. Our ultimate analysis extends this work by directly considering timing and energy in 3-D ICs. In all cases we find that significant performance improvements are possible. In contrast, thermal performance is expected to worsen with the use of 3-D integration. We examine precisely how thermal behavior scales in 3-D integration and determine quantitatively how the temperature may be controlled during the circuit placement process. We also show how advanced packaging(cont.) technologies may be leveraged to maintain acceptable die temperatures in 3-D ICs. Finally, we explore two issues for the future of 3-D integration. We determine how technology scaling impacts the effect of 3-D integration on circuit performance. We also consider how to improve the performance of digital components in a mixed-signal 3-D integrated circuit. We conclude with a look towards future 3-D IC design tools.by Shamik Das.Ph.D

Analysis and Optimisation of an Organic Optical Link

Organic light-emitting diodes (OLEDs) have been historically used extensively for displays, and more recently for lighting applications. However, the low-cost of materials and direct-deposition manufacturing processes involved in organic semiconductor fabrication means that OLEDs are uniquely placed for low-cost integrated optical interconnects. This thesis presents novel high-speed analysis and optimisation of OLEDs for communications purposes. DC and small-signal measurement results for small-molecule OLEDs fabricated by Dr. Kou Yoshida at the University of St. Andrews are presented and are used to inform a detailed 5-layer OLED simulation model. Correlation is drawn between the experimental small signal impedance measurements and the experimental luminescent output, from which a novel electrical model is built to predict bandwidth. Extension of the OLED physical simulation shows for the first time that by using a constant fraction of the overall simulated device resistance (a ‘luminescent resistance’), this RC-based model can be used to predict device small signal bandwidths, which suggests validity of both the simulation and the electrical modelling approach, provided that the exciton lifetime is less than the RC time-constant. This simulation is then used to forecast trends in device performance, allowing traditional inorganic semiconductor engineering tools to be brought into the field of organic device optimisation. Finally, these OLEDs are used in an optical link to provide a world-record equalisation-free OLED communications data rate of 130 Mbps.EPSRC Studentship 1466721 EPSRC via the Ultra Parallel Visible Light Communication Project (EP/K00042X/1

Numerical aerodynamic simulation facility feasibility study

There were three major issues examined in the feasibility study. First, the ability of the proposed system architecture to support the anticipated workload was evaluated. Second, the throughput of the computational engine (the flow model processor) was studied using real application programs. Third, the availability reliability, and maintainability of the system were modeled. The evaluations were based on the baseline systems. The results show that the implementation of the Numerical Aerodynamic Simulation Facility, in the form considered, would indeed be a feasible project with an acceptable level of risk. The technology required (both hardware and software) either already exists or, in the case of a few parts, is expected to be announced this year. Facets of the work described include the hardware configuration, software, user language, and fault tolerance

NASA Tech Briefs, November 2000

Topics covered include: Computer-Aided Design and Engineering; Electronic Components and Circuits; Electronic Systems; Test and Measurement; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Data Acquisition