Enabling Technology in Optical Fiber Communications: From Device, System to Networking

This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking

Tracking and data system support for the Viking 1975 mission to Mars. Volume 1: Prelaunch planning, implementation, and testing

The tracking and data acquisition support for the 1975 Viking Missions to Mars is described. The history of the effort from its inception in late 1968 through the launches of Vikings 1 and 2 from Cape Kennedy in August and September 1975 is given. The Viking mission requirements for tracking and data acquisition support in both the near earth and deep space phases involved multiple radar tracking and telemetry stations, and communications networks together with the global network of tracking stations, communications, and control center. The planning, implementation, testing and management of the program are presented

Terahertz antenna design for future wireless communication

A Terahertz (THz) antenna with a size of a few micrometres cannot be accomplished by just reducing the extent of a traditional metallic antenna down to a couple of micrometres. This approach has several downsides. For example, the low mobility of electrons in nanoscale metallic structures would result in high channel attenuation. Thus, using traditional micrometre metallic antennas for THz wireless communication becomes unfeasible. The THz band refers to the electromagnetic spectrum between the microwave and infrared frequency bands, which is colloquially referred to as the band gap due to the lack of materials and technological advancements. As opposed to their visible-spectrum features, metals such as gold and silver, which typically exhibit surface plasmon polaritons (SPPs), have completely different THz physical properties. 2D materials, which typically refer to single-layer materials, have been the focal point of researchers since the advent of graphene. 2D materials, for example, graphene, perovskite, and MoS2 (TMDs), provide a ground-breaking stage to control the propagation, modulation, and detection of THz waves. Moreover, 2D materials can enable the propagation of SPP waves in the THz band. These materials offer a promise of a future technological revolution. Combined with other profound advantages in lightweight, mechanical flexibility, and environmental friendliness, 2D materials can be used to fabricate low-cost wearable devices. This study also reported CH3NH3PbI3 perovskite as a promising material for THz antennas for wearable applications. CH3NH3PbI3 has a high charge carrier mobility and diffusion length, indicating that this material is a potential candidate for antenna design. The attractive feature about perovskite, graphene and other 2D materials is the ultra-high specific surface areas that enable their energy band structures to be sensitive to external basing. In the literature, scientists have tested a wide range of nano-antenna designs using modelling and simulation approaches. Nano-antenna fabrication and measurement using 2D materials is still the missing piece in the THz band. The design, fabrication, and measurement of THz antennas based on 2D materials for wearable wireless communication is the primary goal of this PhD study, including designing, fabrication, and measurement. In this study, we have designed, fabricated, and measured five different designs using different materials in the THz band, which will pave the way for enabling future THz short-range wireless communication

Achieving Continuous-Wave Lasing for Violet m-plane GaN-Based Vertical-Cavity Surface-Emitting Lasers

Vertical-cavity surface-emitting lasers (VCSELs) are a special class of laser diode that use top-side and bottom-side parallel mirrors to emit a laser beam vertically from the top surface, as compared to conventional edge-emitting lasers that emit light from the sides of the devices. Compared to edge-emitting lasers, VCSELs have many unique attributes, such as a low threshold current that leads to low power consumption, high-speed direct modulation, superior beam quality, and they can be easily arranged into two-dimensional VCSEL arrays for scalable power. This leads to several exciting applications; for example, VCSELs are the key component in the Apple iPhone X that enables Face ID, which allows users to securely unlock their devices simply by looking at their phones. However, the VCSEL market is currently limited to red-emitting and infrared-emitting VCSELs that use GaAs-based and InP-based systems. If shorter wavelength emitting VCSELs could be created, it would open up a whole new world of untapped and exciting applications. For example, blue and green VCSELs could be paired with red VCSELs to create next-generation display and projector technology. The low power consumption and high beam quality of VCSEL-based displays would be particularly promising for virtual and augmented reality systems. Shorter wavelength VCSELs can be created using GaN-based materials, but these devices have been very challenging to create. The first GaN-based VCSEL was demonstrated in 2008, and only eight research groups have demonstrated these devices over the following decade. With the first report in 2012, the University of California, Santa Barbara (UCSB) has been the only group in the United States to create GaN-based VCSELs. Compared to the c-plane GaN VCSELs from all of the other groups, VCSELs from UCSB have used m-plane GaN, which uniquely provides 100% polarized emission for both individual VCSELs and VCSEL arrays. The main problem with GaN VCSELs from UCSB has been their inability to lase under continuous-wave (CW) operation. They could only lase under pulsed operation, which means that these VCSELs would fail if turned on for longer than a fraction of a millisecond. This has been a severe limitation that has prevented most practical applications of these devices. Therefore, the ultimate goal of the research described in this thesis has been to achieve CW lasing. This has been a tremendously difficult goal, and the initial VCSEL designs failed to lase, even under pulsed operation. Despite these initial discouraging results, this experiment was important because it led to an extensive failure analysis that revealed several key problems with the VCSEL design. Surface roughness prior to the DBR mirror deposition turned out to be a major problem that inhibited lasing due to scattering loss and reduced mirror reflectance. After performing experiments to improve the surface morphology, the surface roughness on the p-side was reduced by utilizing an indium flux during MBE tunnel junction regrowth, and the roughness on the n-side was reduced by removing an oxide residue that formed after the photoelectrochemical (PEC) undercut etch to remove the m-plane GaN growth substrate. Another significant problem was VCSEL yield in which only a small percentage of devices successfully transferred onto the flip-chip substrate, and most of those devices were cracked. A series of flip-chip bonding experiments were conducted to optimize the Au-Au thermocompression bond, but the yield only marginally improved at first. The flip-chip bond was also responsible for a severe thermal issue that prevented CW operation in previous devices. Based on thermal modeling in COMSOL, heat generated in the active region could not flow directly downward due to the thermally-insulating bottom DBR, so there was a bottleneck in heat transport through a relatively thin gold contact along the sidewall of the bottom DBR toward the flip-chip substrate. Focused ion beam (FIB) cross-sectioning revealed cracks in that thin metal contact, which were found to significantly impair the VCSEL thermal performance based on COMSOL simulations. Both the VCSEL yield and thermal performance were improved by implementing a new flip-chip bonding design. Instead of Au-Au thermocompression bonding, Au-In solid liquid interdiffusion (SLID) bonding was performed at a much lower temperature and pressure, which greatly improved the VCSEL yield. Furthermore, Au-In SLID bonding significantly improved the VCSEL thermal performance by incorporated a liquid phase during bonding so that the entire bottom DBR was embedded within metal. This led to the world’s first demonstration of CW operation for m-plane GaN VCSELs, and they were able to lase under CW operation for over 20 minutes of continuous testing

Research reports: The 1980 NASA/ASEE Summer Faculty Fellowship Program

The Summer Faculty Fellowship Research Program objectives are: to further the professional knowledge of qualified engineering and science faculty members; to stimulate an exchange of ideas between participants and NASA; to enrich and refresh the research and teaching activities of participants and institutions; and to contribute to the research objectives at the NASA centers. The Faculty Fellows engaged in research projects commensurate with their interests and background and worked in collaboration with a NASA/MSFC colleague

Earth orbital experiment program and requirements study, volume 1, sections 1 - 6

A reference manual for planners of manned earth-orbital research activity is presented. The manual serves as a systems approach to experiment and mission planning based on an integrated consideration of candidate research programs and the appropriate vehicle, mission, and technology development requirements. Long range goals and objectives for NASA activities during the 1970 to 1980 time period are analyzed. The useful and proper roles of manned and automated spacecraft for implementing NASA experiments are described. An integrated consideration of NASA long range goals and objectives, the system and mission requirements, and the alternative implementation plans are developed. Specific areas of investigation are: (1) manned space flight requirements, (2) space biology, (3) spaceborne astronomy, (4) space communications and navigation, (5) earth observation, (6) supporting technology development requirements, (7) data management system matrices, (8) instrumentation matrices, and (9) biotechnology laboratory experiments

Space and Earth Sciences, Computer Systems, and Scientific Data Analysis Support, Volume 1

This Final Progress Report covers the specific technical activities of Hughes STX Corporation for the last contract triannual period of 1 June through 30 Sep. 1993, in support of assigned task activities at Goddard Space Flight Center (GSFC). It also provides a brief summary of work throughout the contract period of performance on each active task. Technical activity is presented in Volume 1, while financial and level-of-effort data is presented in Volume 2. Technical support was provided to all Division and Laboratories of Goddard's Space Sciences and Earth Sciences Directorates. Types of support include: scientific programming, systems programming, computer management, mission planning, scientific investigation, data analysis, data processing, data base creation and maintenance, instrumentation development, and management services. Mission and instruments supported include: ROSAT, Astro-D, BBXRT, XTE, AXAF, GRO, COBE, WIND, UIT, SMM, STIS, HEIDI, DE, URAP, CRRES, Voyagers, ISEE, San Marco, LAGEOS, TOPEX/Poseidon, Pioneer-Venus, Galileo, Cassini, Nimbus-7/TOMS, Meteor-3/TOMS, FIFE, BOREAS, TRMM, AVHRR, and Landsat. Accomplishments include: development of computing programs for mission science and data analysis, supercomputer applications support, computer network support, computational upgrades for data archival and analysis centers, end-to-end management for mission data flow, scientific modeling and results in the fields of space and Earth physics, planning and design of GSFC VO DAAC and VO IMS, fabrication, assembly, and testing of mission instrumentation, and design of mission operations center

Telecommunications Networks

This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing

Studies on natural products: resistance modifying agents, antibacterials and structure elucidation

This thesis describes research starting in 1999 on three areas of natural product science, namely bacterial resistance modifying agents, antibacterials and structure elucidation of natural products. Plants produce an array of structurally-complex and diverse chemical scaffolds and whilst there is an expanding volume of published literature on structure elucidation, there remains a need to understand why these compounds are produced and how they function in terms of biological activity. That can only be properly realised by a full and determined attempt at structure elucidation. This is an important concept as molecular structure describes and precedes function. The chirality and functional group chemistry of natural products defines the way in which a compound specifically binds to a receptor, protein or drug target. My independent research career started with studies on the ability of plant extracts and phytochemicals to modulate the activity of antibiotics that are substrates for bacterial multidrug efflux. These investigations are described in the first section, “Natural Product Resistance Modifying Agents”. Studies were, in the first instance, simple assays to look at potentiation and synergy of extracts and pure phytochemicals to potentiate the activity of antibiotics against resistant bacteria. This research evolved to study efflux inhibition, where we learnt much from the collaborations with Professors Piddock (Birmingham), Kaatz (Wayne State) and Bhakta (Birkbeck). Latterly, we were inspired by the highly imaginative and creative work of Dr Paul Stapleton (UCL), to study the plasmid transfer inhibitory effects of natural products; the rationale being that plasmids carry antibiotic-resistance genes and virulence factors. Inhibition of transfer could result in a reduction in the spread of antibiotic resistance and a reduction in pathogenicity. The second section of this thesis describes antibacterial natural products that were evaluated against clinically-relevant species of bacteria, in the main Gram-positive organisms such as Staphylococcus aureus and its methicillin- (MRSA) and multidrug-resistant variants and Mycobacterium tuberculosis, the causative agent of tuberculosis, which still continues to affect millions of people globally and for which antibiotic resistance is considerable. The papers described in this section detail the extraction of the plant and the bioassay-guided isolation of the active compounds, which were then subjected to structure elucidation, using in the majority of cases, Nuclear Magnetic Resonance (NMR) spectroscopy, High-Resolution Mass Spectrometry, and Infrared and Ultraviolet-Visible Spectroscopy. Natural products from the acylphloroglucinol, terpenoid, polyacetylene, alkaloid and sulphide classes are well represented in these publications with some of these antibacterial natural products displaying minimum inhibitory concentrations (MIC) values of less than 1 mg/L against MRSA and Mycobacterium tuberculosis strains. These activity levels approach those of existing clinically used antibiotics and this highlights the value of plant natural products as a resource for antibacterial templates. Mechanistic studies have also been conducted on selected compounds, for example the natural products from Hypericum acmosepalum were found to inhibit ATP- dependent MurE ligase, a key enzyme involved in bacterial cell wall biosynthesis. Other examples included the main component of cinnamon (Cinnamomum zeylanicum), an ancient medicinal material cited in the Bible in Exodus, which has been used in antiquity as an anti-infective substance. The main compound from this medicinal material is trans-cinnamaldehyde, a simple phenylpropanoid which has been shown to inhibit Acetyl-CoA Carboxylase, a pivotal enzyme that catalyses the first committed step in fatty acid biosynthesis in all animals, plants and bacteria. In collaboration with the marine natural product chemist Professor Vassilios Roussis, we have also been able to characterise the antibacterial activities of marine plants, particularly compounds of the diterpene class that display promising levels of antibacterial activity against MRSA and S. aureus strains. Work on the antibacterial properties of Cannabis sativa showed that some of the main cannabinoids display excellent potency towards drug-resistant variants of S. aureus and support the ancient medicinal usage of Cannabis as an anti-infective and wound healing preparation. The acylphloroglucinol class of plant natural products are also noteworthy, particularly from Hypericum and Mediterranean medicinal plant species such as Myrtle (Myrtus communis), again with MIC values reaching 1 mg/L against pathogenic bacteria. We synthesised some of these acylphloroglucinols and made analogues and not surprisingly, were unable to improve the activity as nature really is the best chemist of all. The final section describes early and continuing research into the isolation and structure elucidation of natural products from plants and microbes. The rationale for this research is manifold: training for isolation to understand the medicinal use of a plant or microbe, chemotaxonomic investigations, the ecological relevance of phytochemicals in plants that are halophytic and xerophytic and in some cases just plain academic curiosity. These studies use classical phytochemical techniques to isolate and determine the structures of the species of investigation and where possible, absolute stereochemistry is undertaken. It should be noted however that isolation can be exceptionally challenging and frustrating. This can be due to the paucity of biomass, low concentrations of compounds, complexity of the resulting natural product mixtures and finally a lack of chemical stability of the products. All of these issues need to be faced before structure determination can even be attempted. A word of caution is therefore needed to the young natural product chemist embarking on their first isolation project. However, words of encouragement are also needed: the isolation of new, chemically complex and exquisitely biologically active molecules is a beautiful endeavour and exceptionally rewarding on many levels.This thesis describes research starting in 1999 on three areas of natural product science, namely bacterial resistance modifying agents, antibacterials and structure elucidation of natural products. Plants produce an array of structurally-complex and diverse chemical scaffolds and whilst there is an expanding volume of published literature on structure elucidation, there remains a need to understand why these compounds are produced and how they function in terms of biological activity. That can only be properly realised by a full and determined attempt at structure elucidation. This is an important concept as molecular structure describes and precedes function. The chirality and functional group chemistry of natural products defines the way in which a compound specifically binds to a receptor, protein or drug target. My independent research career started with studies on the ability of plant extracts and phytochemicals to modulate the activity of antibiotics that are substrates for bacterial multidrug efflux. These investigations are described in the first section, “Natural Product Resistance Modifying Agents”. Studies were, in the first instance, simple assays to look at potentiation and synergy of extracts and pure phytochemicals to potentiate the activity of antibiotics against resistant bacteria. This research evolved to study efflux inhibition, where we learnt much from the collaborations with Professors Piddock (Birmingham), Kaatz (Wayne State) and Bhakta (Birkbeck). Latterly, we were inspired by the highly imaginative and creative work of Dr Paul Stapleton (UCL), to study the plasmid transfer inhibitory effects of natural products; the rationale being that plasmids carry antibiotic-resistance genes and virulence factors. Inhibition of transfer could result in a reduction in the spread of antibiotic resistance and a reduction in pathogenicity. The second section of this thesis describes antibacterial natural products that were evaluated against clinically-relevant species of bacteria, in the main Gram-positive organisms such as Staphylococcus aureus and its methicillin- (MRSA) and multidrug-resistant variants and Mycobacterium tuberculosis, the causative agent of tuberculosis, which still continues to affect millions of people globally and for which antibiotic resistance is considerable. The papers described in this section detail the extraction of the plant and the bioassay-guided isolation of the active compounds, which were then subjected to structure elucidation, using in the majority of cases, Nuclear Magnetic Resonance (NMR) spectroscopy, High-Resolution Mass Spectrometry, and Infrared and Ultraviolet-Visible Spectroscopy. Natural products from the acylphloroglucinol, terpenoid, polyacetylene, alkaloid and sulphide classes are well represented in these publications with some of these antibacterial natural products displaying minimum inhibitory concentrations (MIC) values of less than 1 mg/L against MRSA and Mycobacterium tuberculosis strains. These activity levels approach those of existing clinically used antibiotics and this highlights the value of plant natural products as a resource for antibacterial templates. Mechanistic studies have also been conducted on selected compounds, for example the natural products from Hypericum acmosepalum were found to inhibit ATP- dependent MurE ligase, a key enzyme involved in bacterial cell wall biosynthesis. Other examples included the main component of cinnamon (Cinnamomum zeylanicum), an ancient medicinal material cited in the Bible in Exodus, which has been used in antiquity as an anti-infective substance. The main compound from this medicinal material is trans-cinnamaldehyde, a simple phenylpropanoid which has been shown to inhibit Acetyl-CoA Carboxylase, a pivotal enzyme that catalyses the first committed step in fatty acid biosynthesis in all animals, plants and bacteria. In collaboration with the marine natural product chemist Professor Vassilios Roussis, we have also been able to characterise the antibacterial activities of marine plants, particularly compounds of the diterpene class that display promising levels of antibacterial activity against MRSA and S. aureus strains. Work on the antibacterial properties of Cannabis sativa showed that some of the main cannabinoids display excellent potency towards drug-resistant variants of S. aureus and support the ancient medicinal usage of Cannabis as an anti-infective and wound healing preparation. The acylphloroglucinol class of plant natural products are also noteworthy, particularly from Hypericum and Mediterranean medicinal plant species such as Myrtle (Myrtus communis), again with MIC values reaching 1 mg/L against pathogenic bacteria. We synthesised some of these acylphloroglucinols and made analogues and not surprisingly, were unable to improve the activity as nature really is the best chemist of all. The final section describes early and continuing research into the isolation and structure elucidation of natural products from plants and microbes. The rationale for this research is manifold: training for isolation to understand the medicinal use of a plant or microbe, chemotaxonomic investigations, the ecological relevance of phytochemicals in plants that are halophytic and xerophytic and in some cases just plain academic curiosity. These studies use classical phytochemical techniques to isolate and determine the structures of the species of investigation and where possible, absolute stereochemistry is undertaken. It should be noted however that isolation can be exceptionally challenging and frustrating. This can be due to the paucity of biomass, low concentrations of compounds, complexity of the resulting natural product mixtures and finally a lack of chemical stability of the products. All of these issues need to be faced before structure determination can even be attempted. A word of caution is therefore needed to the young natural product chemist embarking on their first isolation project. However, words of encouragement are also needed: the isolation of new, chemically complex and exquisitely biologically active molecules is a beautiful endeavour and exceptionally rewarding on many levels