The ability of a machine to synthesize textual output in a form of human language is a long-standing goal in a field of artificial intelligence and has wide-range of applications such as spell correction, speech recognition, machine translation, abstractive summarization, etc. The statistical approach to enable such ability mainly involves...
This thesis reports on the use of optical antennas, and more broadly, metal optics for the engineered collection and enhancement of infrared photodetectors. These ideas would be useful in enhancing at other wavelengths and other types of detectors, but this work is specifically focused on the Quantum Well Infrared Photodetector...
As Power and Energy become the limiting factors for computer designs and systems, a holistic approach for tackling inefficiencies needs to be adopted. Computations need to be classified based on their importance and impact on the end quality, power consumption, and runtime so that the system can perform the needed...
A practical challenge in wireless communication systems is acquisition of channel state information at the transmitter and the receiver. In this thesis, we address the problem of training and limited-rate feedback optimization for fading channels. In a wideband (multi-carrier) channel, given limited coherence time and power, only a finite number...
Several challenges exist in cardiac magnetic resonance imaging (MRI) as a result of the constant motion of the heart. In order to create a cardiac image with both high spatial and temporal resolution, MR data must be obtained from multiple cardiac cycles; therefore, a means of synchronization for segmented acquisition...
The III-Nitride material system has already proven to be commercially viable for blue light emitting diodes (LEDs), blue laser diodes (LDs), and near UV photodetectors. Continued interest in this field has driven the desire for even lower emission and detection cut-off wavelengths into the solar-blind / deep UV portion of...
This thesis focuses on resource allocation in wireless communication and networking. Resource allocation has been studied widely, for example, to maximize the system-wide throughput or to minimize the average delay per user. Moreover, the utility-based framework is becoming an important tool for addressing fairness and Quality-of-Service (QoS) for individual users....
All-optical switches have far reaching applications in both quantum and classical information processing. Most current all-optical switches depend on intense interactions between light and nonlinear media which may be extremely inefficient. The need for high switching beam powers have prevented all-optical switching from being very useful in most applications. Our...
As device sizes decrease, more functionality can be placed in an integrated circuit. Therefore, the design complexity of these circuits increases. To deal with complexity, designers move to higher abstraction levels. Currently, the highest abstraction level is the system-level. In our work we investigate the synthesis and verification problem at...
The semiconductor-based Quantum Cascade Laser (QCL) offers several key advantages over gas lasers, solid-state lasers, and other semiconductor-based mid-infrared lasers. While the QCL has historically operated best in the λ ~ 7-9 μm range using InP-based materials, a major challenge has been to achieve a high-power, room-temperature continuous-wave (CW) operation...
Atrial fibrillation (AF) is the most common supraventricular tachyarrhythmia and its prevalence is expected to increase with the aging population. However, the mechanisms AF initiation, maintenance and termination are not completely understood. The surface electrocardiogram (ECG) characteristics are a direct reflection of pathophysiologic events in the atria and can be...
As we move into deeper sub-micron technologies, the complexity of pushing the circuit performance further is becoming an important obstacle. To achieve better performance, there is an increasing need for collaboration of higher level (e.g. microarchitecture-level) and circuit level optimizations. Traditionally for a computer system, applications lie at the top...
Process scaling has enabled the production of integrated circuits with millions of transistors. System-on-a-Chip becomes feasible as more functionalities can be packed into a single chip. As the human brain power is limited, the design process of such sophisticated systems should be automated in order to meet the stringent design...
The growing technological industry is demanding the development of powerful and smaller devices. Dielectric thin-films can play an important role to help push towards achieving these goals. However, their advantage of high-quality material and low material costs compared to bulk can only be achieved with consideration of the technique, conditions,...
Visual object tracking, i.e. consistently inferring the motion of a desired target from image sequences, is a must-have component to bridge low-level image processing techniques and high-level video content analysis. This has been an active and fruitful research topic in the computer vision community for decades due to both its...
Integrated circuits have been continuously scaled to increase speed and integration density as a means to improve the performance or pack more functionality. However, an extremely enormous amount of effort is needed to further scale the dimensions in deep submicron technologies. As technology scaling is slowing down and design complexity...
Integrated circuits have been continuously scaled to increase speed and integration density as a means to improve the performance or pack more functionality. However, an extremely enormous amount of effort is needed to further scale the dimensions in deep submicron technologies. As technology scaling is slowing down and design complexity...
As manufacturing technology moves toward fundamental limits of silicon CMOS processing, it is increasingly important to utilize the full potential of available transistors and interconnects. While manufacturing technology faces fundamental limits inherent in physical laws or material properties, design and verification technology faces fundamental limitations inherent in the computational intractability...
Leakage currents limit the operation of high performance type II InAs/GaSb superlattice photodiode technology. Surface leakage current becomes a dominant, limiting factor to the ideal performance of a photodiode, especially at the scale of a focal plane array pixel (< 25 µm), and must be addressed. A reduction of the...
Multi-hop wireless networks hold promise for increasing network capacity, lowering power requirements, and improving coverage over traditional cellular networks. However, their widespread adoption is hampered by challenges that include: 1) unreliable and complex routing protocols due to the transient nature of wireless nodes, 2) difficulties in guaranteeing quality of service...
The important application for the infrared photodetectors is mainly thermal imaging by focal plane arrays (FPAs) for military and commercial purposes. So far, most mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) FPAs are based either on HgCdTe (MCT) or quantum well infrared photodetectors (QWIPs). Even though those technologies are well...
An efficient unified incremental high-level and physical-level synthesis algorithm was presented in Chapter 2, which enable the tight integration between high-level and physical-level design. Chapter 3 presented a temperature-aware high-level synthesis algorithm built upon the framework of Chapter 2. Temperature variations and hot spots account for reliability issue and require...
I/O performance has perpetually lagged well behind that of processors. This gap is made even more pronounced in the field of high-performance computing. While simply adding more network bandwidth and increasing the number of storage units is a simple way to increase theoretical peak I/O bandwidth, the software libraries for...
With aggressive scaling down of feature sizes in VLSI fabrication, process variations, crosstalk and buffering have become critical issues to achieve timing closure in VLSI designs. Timing analysis and optimization techniques need to consider each of them and also their interactions. There are many statistical timing analysis researches to handle...
Video transmission over wireless networks to multiple mobile users has remained a challenging problem due to potential limitations on bandwidth and the time-varying nature of wireless channels. Recent advances in wireless access technologies, such as, HSDPA and IEEE 802.16, are targeted at achieving higher throughput over wireless networks. Meanwhile, advances...
FPGAs are evolving at a rapid pace with improved performance and logic density. However, power efficiency of FPGAs has continuously lagged behind, and hence power optimization of FPGAs is crucial. Trends in technology scaling makes leakage power a serious concern for designers; on the other hand, routing power is the...
The emergence of lightwave communication and computing, and applications in nanophotonics require an understanding of complex electromagnetic wave phenomena in linear and nonlinear materials having frequency-dependent and intensity-dependent polarizations. Both the complexity of the underlying physics and the problems required for modern engineering applications necessitate understanding the vector-nature of the...
New telecommunication techniques utilizing distinctive quantum properties, e.g., measurement uncertainties and entanglement, extend the capabilities of existing systems. Quantum cryptography, as an example, provides physical layer security enforced by fundamental physical laws, while modern cryptographic techniques rely on assumptions of intractability of certain mathematical problems with limited computational power.
Rapid...
As technology moves into deep submicron and nanoscale era, undesirable trends such as increasing power density, leakage power, and temperature variation within chips have made thermal effects emerge as a major bottleneck in further technology scaling. Thermal effects are no longer considered as just a reliability issue, but it also...
Next generation of high performance nano-optoelectronic integrated circuits will require an integral combination of highly efficient all-optical nanophotonic devices and electrically-pumped nanophotonic devices, which will enable the chip to process optical information all optically with ultrafast speed and electro-optically to interface with the electronic control plane. The realizations of such...
Entangled photons serve as an important tool in the field of quantum information processing. Traditionally, spontaneous parametric down-conversion (SPDC) in second-order nonlinear crystals has been the workhorse source for generating entangled photons. However, those SPDC-generated photons are notoriously difficult to couple into single-mode optical fibers due to mode mismatch, thus...
The study of III-Nitride based optoelectronics devices is a maturing field, but there are still many underdeveloped areas in which to make a contribution of new and original research. This work specifically targets the goals of realizing high-efficiency back-illuminated solar-blind photodetectors, solar-blind focal plane arrays, and visible- and solar-blind Avalanche...
Wave propagation at the bottom of the electromagnetic spectrum (below 300 kHz) in the Earth-ionosphere system is a problem having a rich history of theoretical investigation extending over many decades. Propagation within this system involves complex interactions of electromagnetic waves with the lithosphere, oceans, and ionosphere, leading to resonances that...
The work presented here represents a series of research projects that are unified in their goal: to use volume holographic gratings to enhance traditional signal processing applications in ways that would otherwise not be possible. To this end, we have completed work that can be classified into four different projects....
The rapid growth of digital imaging technology and the accumulation of large collections of digital images has created the need for efficient and intelligent schemes for content-based image retrieval. Our goal is to organize the contents semantically, according to meaningful categories. We present a new approach for semantic classification that...
Analytical lower and upper bounds for the average error probability in M-ary quantum detection are derived. The upper bound is valid when the state ensemble, which can consist of pure or mixed states, satisfies a certain linear independence condition. The lower bound is generally valid and also has a classical...
This thesis discusses the application of advanced digital signal and image processing techniques, particularly the technique known as super-resolution (SR), to enhance the imagery produced by cameras mounted on an airborne platform such as an unmanned aircraft system (UAS). SR is an image processing technology applicable to any digital, pixilated...
This dissertation reports on novel theoretical concepts as well as experimental efforts toward laser cooling of semiconductors. The use of quantum well system brings the opportunity to engineer bandstructure, effective masses and the spatial distribution of electrons and holes. This permits the incorporation of novel quantum mechanical phenomena to manipulate...