Investigation of in-situ parameter control in novel semiconductor optical amplifiers

Fibre optic networks form the backbone of modern communications systems. As demand for ever increasing bandwidth continues to grow, technologies that enable the expansion of optical networks will be the key to future development. The semiconductor optical amplifier (SOA) is a technology that may be crucial in future optical networks, as a low cost in-line amplifier or as a functional element. As fibre networks extend closer to the end user, economical ways of improving the reach of these networks are important. SOAs are small, relatively inexpensive and can be readily integrated in photonic circuits. Problems persist with the development of SOAs, however, in the form of a relatively high noise figure and low saturation output power, which limits their use in many circumstances. The aim of this thesis is to outline a concept for control of these parameters such that the SOA can achieve the performance required. The concept relies on the control of the carrier density distribution in the SOA. The basic characteristics of the SOA and how they are affected by changes in the carrier density are studied. The performance of the SOA in linear and high power transmission of CW and pulsed signals is determined. Finally, the wavelength conversion characteristics of the SOA are outlined. The role of the carrier density control in shaping all of these characteristics will be explained

Novel design for noise controlled semiconductor optical amplifier

The use of semiconductor optical amplifiers (SOA) in optical communications networks has so far been limited due to their inherent large noise figure (NF) compared to Erbium Doped Fibre Amplifiers. Therefore improvement of the noise performance of SOAs is critical to their widespread adoption in future networks. We propose to reduce the NF of the SOA by introducing a lasing cavity lateral to the axis of amplification of the device. The carrier density within the cavity is clamped at the lasing threshold. It is thus possible to engineer the carrier density distribution along the active waveguide by controlling the cavity design. According to our simulations, some of the cavity designs lead to a reduction of the noise figure in this novel SOA

Semiconductor optical amplifier-based heterodyning detection for resolving optical terahertz beat-tone signals from passively mode-locked semiconductor lasers

An all-optical heterodyne approach based on a room-temperature controlled semiconductor optical amplifier (SOA) for measuring the frequency and linewidth of the terahertz beat-tone signal from a passively mode-locked laser is proposed. Under the injection of two external cavity lasers, the SOA acts as a local oscillator at their detuning frequency and also as an optical frequency mixer whose inputs are the self-modulated spectrum of the device under test and the two laser beams. Frequency and linewidth of the intermediate frequency signal and therefore, the beat-tone signal are resolved by using a photodiode and an electrical spectrum analyze

Chronic brain stimulation using Micro-ECoG devices

Recording and stimulating brain activity has had great success both as a research tool and as a clinical technique. Neural prosthetics can replace limbs, restore hearing, and treat disorders like Parkinson’s and epilepsy, but are relatively crude. Current neural prosthetic systems use penetrating electrodes to achieve high precision, but the invasive nature of these devices provoke a strong immune response that limits chronic use. (Polikov et al) In our study we evaluate micro-electrocortiographic (micro-ECoG) devices which sit under the skull and on the surface of the brain for stimulation over chronic timescales. We anticipate these devices with their less invasive placement will evoke less extreme immune responses compared to penetrating electrodes and allow for stable stimulation over long periods of time (months to years). These devices were developed by the NITRO Lab of University of Wisconsin. (Thongpang et al) In short, Sprague Dawley rats were implanted with micro-ECoG devices over either somatosensory or auditor cortex. They were stimulated electrically through these devices on a daily basis to evaluate their chronic performance in vivo. Sensitivity to stimulation was determined via an operant behavioral task and the implants’ electrical properties were measured daily to monitor functionality and approximate of the immune response. After at least two months of implantation, animals were perfused and a histological analysis was performed to evaluate the chronic immune response. From preliminary results we expect to see that the micro-ECoG devices are capable of long term stimulation and evoke a smaller immune response from the brain than penetrating neural implants. In addition, we have found that removing the dura in rats for device implantation causes significant brain swelling, which indicates a strong immune response preventing effective stimulation. This research shows that micro-ECoG devices can chronically stimulate brain tissue and show great promise as a less invasive method of neural interfacing compared to traditional penetrating electrodes

Ballistics Analysis of Orion Crew Module Separation Bolt Cover

NASA is currently developing a new crew module to replace capabilities of the retired Space Shuttles and to provide a crewed vehicle for exploring beyond low earth orbit. The crew module is a capsule-type design, which is designed to separate from the launch vehicle during launch ascent once the launch vehicle fuel is expended. The separation is achieved using pyrotechnic separation bolts, wherein a section of the bolt is propelled clear of the joint at high velocity by an explosive charge. The resulting projectile must be contained within the fairing structure by a containment plate. This paper describes an analytical effort completed to augment testing of various containment plate materials and thicknesses. The results help guide the design and have potential benefit for future similar applications

Kinetic and structural mechanism for DNA unwinding by a non-hexameric helicase

UvrD, a model for non-hexameric Superfamily 1 helicases, utilizes ATP hydrolysis to translocate stepwise along single-stranded DNA and unwind the duplex. Previous estimates of its step size have been indirect, and a consensus on its stepping mechanism is lacking. To dissect the mechanism underlying DNA unwinding, we use optical tweezers to measure directly the stepping behavior of UvrD as it processes a DNA hairpin and show that UvrD exhibits a variable step size averaging ~3 base pairs. Analyzing stepping kinetics across ATP reveals the type and number of catalytic events that occur with different step sizes. These single-molecule data reveal a mechanism in which UvrD moves one base pair at a time but sequesters the nascent single strands, releasing them non-uniformly after a variable number of catalytic cycles. Molecular dynamics simulations point to a structural basis for this behavior, identifying the protein-DNA interactions responsible for strand sequestration. Based on structural and sequence alignment data, we propose that this stepping mechanism may be conserved among other non-hexameric helicases

Business Models for Energy Entrepreneurship in Emerging Markets

Access to electricity produces greater levels of economic value and increases the quality of life in emerging markets across the globe. Emerging economies have surpassed developed nations in clean energy investment and deployment1 , but based on our review of the literature, there is a lack of high-level study on the factors that most affect the success of these businesses. The goal of this project is to identify these success factors, and use them to inform entrepreneurs’ strategic decision-making as well as elucidate the environments in which these ventures have a higher probability of success. By better understanding what drives success in the renewable energy industry, both entrepreneurs and key stakeholders such as policy makers, investors, and interested non-governmental organizations (NGOs) can better prioritize their efforts and investments to drive increased levels of clean energy adoption. This project focuses on clean energy business models in two emerging economies: India and Uganda. These countries have significant differences in levels of access to energy and development of their entrepreneurial landscapes, and therefore, provide a broad scope for analysis. This report presents an overview of existing empirical research on factors that hinder or increase success of business models, identifies potential gaps in this research, and presents analysis based on qualitative, in-country interviews conducted by our team. Based on a comparative analysis between the literature review and interview findings, the team drew conclusions about factors that would benefit from better coordination and investment from industry players. The team also identified aspects of the entrepreneurial experience in developing countries that are strong candidates for further academic research. Throughout the project, entrepreneurs and industry experts (such as the stakeholders above) highlighted several of the key topics identified in existing research, including the challenge of attracting private investment, strategies for revenue collection given limited ability to pay among customers, the effect of domestic energy policy, and the industry’s lack of institutional support, whether it be nonexistent or ineffective small business associations, trade associations, lobbying groups, etc. While it was reassuring to see entrepreneur and stakeholder interviews validate what had been uncovered in the literature review, the key value created by this project was largely the nuance the interviews provided regarding the structural issues that were inhibiting growth for the renewable and clean energy industries, and provide context around how some of these issues were overcome in India and Uganda. Our research questions aimed to understand how entrepreneurs can directly improve their prospects for success and where their efforts require coordination with other partners in the renewable energy value chain or key policymakers. The interviews revealed a clear distinction between the factors that entrepreneurs and industry experts found to be most relevant and important to the success of clean energy entrepreneurs. Factors such as positioning/strategy, company structure, ability to collect revenue, and business model flexibility were by far more relevant for entrepreneurs than industry experts. This understanding of which factors are more directly in entrepreneurs’ control can allow them to prioritize which factors to focus their attention and resources on. In contrast, industry experts regularly mentioned factors that were not top of mind for entrepreneurs in interviews such as domestic energy policy, customer financial resources, and distribution and utility infrastructure. Despite the relative dichotomy between entrepreneurs and industry experts, there was some overlap among what factors the two groups found to be the most important. These factors include talent attraction and retention, accessibility of private investment, competitive landscape, consumer education and strategic partnerships. The overlapping factors indicate the significance of these challenges, and highlights the potential areas where strategic partnerships would be the most beneficial to foster a healthier entrepreneurial ecosystem. Overall, the interviews raised new issues that were not discussed as in-depth in the literature. For example, the conclusion that there is a lack of product awareness and trust among most consumers, and that regulatory uncertainty of even the most well-intentioned policies can be extremely detrimental. In India, there were difficulties retaining employees. In Uganda, there appears to be a weak pipeline of educated, local talent. These issues demand comprehensive solutions that can only be realized by greater cooperation and coordination between entrepreneurs, industry experts, and policy makers. In sum, the hope is that this research will inform market players of key factors of entrepreneurial success and act as a catalyst for future research. In particular, what factors do entrepreneurs and industry experts see affecting success, where do they see greater opportunities for coordination, and how are the Indian and Ugandan experiences representative of other emerging markets?Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttps://deepblue.lib.umich.edu/bitstream/2027.42/148815/1/Business Models for Energy Entrepreneurship in Emerging Markets_P46.pd

Noise controlled semiconductor optical amplifier based on lateral cavity laser

Experimental characterisation of a novel noise-controlled semiconductor optical amplifier (NCSOA) is presented. The design utilises grooves etched parallel to the active waveguide, at the output sections of the NCSOA, so as to induce lasing laterally to the propagation axis. This clamps the carrier density in a relevant region, allowing for the engineering of a specific longitudinal carrier density profile, corresponding to an improved noise figure performance. Results have demonstrated the effectiveness of carrier density profile engineering as a means of reducing the noise figure in semiconductor optical amplifier

Impact of bias current distribution on the noise figure and power saturation of a multi-contact semiconductor optical amplifier

We present an experimental investigation of a multi-contact semiconductor optical amplifier. This first-generation device allows for direct control of the carrier density profile along the length of the waveguide. This is used to control the device noise figure, with a minimum value of 5 dB observed at a gain of 15 dB for an optimum carrier density profile. The opposite carrier density profile results in an increase of the power saturation by 3 dB