Optical multi-context scrubbing operation on a redundant system

This paper presents a proposal of the world-first optical multi-context scrubbing operation on a redundant system that can maintain the state of a sequential circuit and the operation continuously without any interruption on a radiation-hardened optically reconfigurable gate array even after a permanent failure suddenly happens on the sequential circuit or a flip-flop by radiation. Up to now, a high-speed optical scrubbing operation has been demonstrated on a radiation-hardened optically reconfigurable gate array. In addition, a multi-context scrubbing operation based on the high-speed optical scrubbing operation has already been demonstrated. Although the multi-context scrubbing operation presents the benefit that it can treat both soft errors and permanent failures caused by radiation simultaneously, the conventional contributions have never presented how to maintain the state of a sequential circuit after a permanent failure occurs on flip-flops. Therefore, in the conventional multi-context scrubbing operation, all the operations must be restarted from the initial condition each time a permanent failure occurs on a programmable gate array. As a result, conventional multi-context scrubbing operations could not be applied for real-time systems. The proposed optical multi-context scrubbing method that can solve the issue has been experimentally evaluated on a radiation-hardened optically reconfigurable gate array

Configuration Sharing Optimized Placement and Routing

Reconfigurable systems have been shown to achieve very high computational performance. However, the overhead associated with reconfiguration of hardware remains a critical factor in overall system performance. This paper discusses the development and evaluation of a technique to minimize the delay associated with reconfiguration based upon optimized sharing of configuration bit streams between design contexts. This is achieved through modified placement and routing algorithms

Fault Tolerance in Programmable Metasurfaces: The Beam Steering Case

Metasurfaces, the two-dimensional counterpart of metamaterials, have caught great attention thanks to their powerful control over electromagnetic waves. Recent times have seen the emergence of a variety of metasurfaces exhibiting not only countless functionalities, but also a reconfigurable or even programmable response. Reconfigurability, however, entails the integration of tuning and control circuits within the metasurface structure and, as this new paradigm moves forward, new reliability challenges may arise. This paper examines, for the first time, the reliability problem in programmable metamaterials by proposing an error model and a general methodology for error analysis. To derive the error model, the causes and potential impact of faults are identified and discussed qualitatively. The methodology is presented and instantiated for beam steering, which constitutes a relevant example for programmable metasurfaces. Results show that performance degradation depends on the type of error and its spatial distribution and that, in beam steering, error rates over 10% can still be considered acceptable

Synchronous OEIC integrating receiver for optically reconfigurable gate arrays

A monolithically integrated optoelectronic receiver with a low-capacitance on-chip pin photodiode is presented. The receiver is fabricated in a 0.35µm opto-CMOS process fed at 3.3V and due to the highly effective integrated pin photodiode it operates at µW. A regenerative latch acting as a sense amplifier leads in addition to a low electrical power consumption. At 400 Mbit/s, sensitivities of -26.0dBm and -25.5dBm are achieved, respectively, for ¿ = 635nm and ¿ = 675nm (BER =10-9) with an energy efficiency of 2 pJ/bit

Parallel and Distributed Computing

The 14 chapters presented in this book cover a wide variety of representative works ranging from hardware design to application development. Particularly, the topics that are addressed are programmable and reconfigurable devices and systems, dependability of GPUs (General Purpose Units), network topologies, cache coherence protocols, resource allocation, scheduling algorithms, peertopeer networks, largescale network simulation, and parallel routines and algorithms. In this way, the articles included in this book constitute an excellent reference for engineers and researchers who have particular interests in each of these topics in parallel and distributed computing

Doctor of Philosophy

dissertationDriven by a myriad of potential applications such as communications, medical imaging, security, spectroscopy, and so on, terahertz (THz) technology has emerged as a rapidly growing technological field during the last three decades. However, since conventional materials typically used in microwave and optical frequencies are lossy or do not effectively respond at these frequencies, it is essential to find or develop novel materials that are suitable for device applications in the THz range. Therefore, there is wide interest in the community in employing novel naturally-occurring materials, such as 2D materials, as well as in designing artificial metamaterial structures for THz applications. Here, we combined both of these approaches so to develop reconfigurable THz devices capable of providing amplitude modulation, phase modulation, and resonance frequency tuning. First, graphene is employed as the reconfigurable element in metamaterial phase modulators. For this purpose, we propose the use of unit cells with deep-subwavelength dimensions, which can have multiple advantaged for beam shaping applications. The analyzed metamaterials have one of the smallest unit cell to wavelength ratios reported or proposed todate at THz frequencies. By systematic analysis of the geometrical tradeoffs in these devices it is found that there is an optimal unit cell dimension, corresponding roughly to ~λ/20, which can deliver the best performance. In addition to this, we explored other applications of graphene in metamaterial devices, including amplitude modulation and resonance-shifting. These studies motivated us to analyze what is the most suitable role of graphene from a THz device perspective: is graphene a good plasmonic material? Or it is better suited as a reconfigurable material providing tunability to otherwise passive metallic structures? Our studies show that the Drude scattering time in graphene is an important parameter in this regard. In order to attain strong plasmonic resonances graphene samples with τ >> 1ps are required, which is challenging in large area CVD samples. But graphene is just one example of a wider class of 2D materials. In this work we also studied for the first time the application of 2D materials beyond graphene as reconfigurable elements in THz devices. For this purpose, Molybdenum Disulfide (MoS2) was employed as the reconfigurable element in cross-slot metamaterial amplitude modulators. Our results evidence that smaller insertion loss is possible when employing 2D materials with a bandgap, such as MoS2, rather than a zero-gap material such as graphene. Furthermore, because of a stronger optical absorption active control of the metamaterial properties is possible by altering the intensity of an optical pump. We later investigate and discuss transparent conductive oxides (TCOs), which constitute an interesting choice for developing visible-transparent THz-functional metamaterial devices for THz applications. These materials show a metallic THz response and thus can substitute the metal patterns in metamaterial devices. In our particular studies we analyzed samples consisting of: (i) two-dimensional electron gases at the interface between polar/nonpolar complex oxides having record-high electron density, and (ii) thin-films of La-doped BaSnO3 having record-high conductivity in a TCO. These materials exhibit a flat THz conductivity across a broad terahertz frequency window. As a result of their metal-like broadband THz response, we demonstrate a visible-transparent THz-functional electromagnetic structure consisting of a wire-grid polarizer