A study on the wireless power transfer efficiency of electrically small, perfectly conducting electric and magnetic dipoles

This paper presents a general theoretical analysis of the Wireless Power Transfer (WPT) efficiency that exists between electrically short, Perfect Electric Conductor (PEC) electric and magnetic dipoles, with particular relevance to near-field applications. The figure of merit for the dipoles is derived in closed-form, and used to study the WPT efficiency as the criteria of interest. The analysis reveals novel results regarding the WPT efficiency for both sets of dipoles, and describes how electrically short perfectly conducting dipoles can achieve efficient WPT over distances that are considerably greater than their size

Study of wireless power transfer link with metallic plates

In this paper, the wireless power transfer link with metallic plates is studied. By enforcing the boundary conditions along metallic surface, the magnetic fields are well confined between two plates and its flux focusing can be also improved. Meanwhile, the large metallic plates can also help to achieve higher transfer efficiency of the wireless power transfer link. Based on the filter theory, these enhanced field intensity effectively enlarge the dynamic range of coupling degree, thus improving the efficiency of the energy transmission. Finally, a 40.68MHz wireless transfer link with the highest measured efficiency of 86.56% is obtained and demonstrated. © 2013 IEEE.published_or_final_versio

Development of semiconductor light sources for photonic-enabled quantum communication

Quantum information technologies have attracted tremendous attentions and development efforts by worldwide research organizations and governments in the past decades. It comprises the generation, manipulation, and transfer of quantum bits `qubits' based on the laws of quantum mechanics, enabling the applications of quantum metrology, quantum computation, quantum communication, etc. As one of the frontier quantum technologies, quantum communication features unconditionally secure data transfer between parties over long distance in theory, which can be accomplished through quantum state of light photons, due to their weak interaction with the environment and their remaining coherence over long distance. Meanwhile, quantum repeaters, similar as amplifier in classical communication are believed to be indispensable components to address the photon absorption and decoherence in noisy quantum channels, which scales exponentially with the distance. Quantum repeaters generally consist of three basic elements, namely entanglement swapping, entanglement purification, and quantum memories. In spite of significant breakthroughs achieved with a variety of optical protocols theoretically and experimentally, lack of near-perfect deterministic light sources with fast repetition rates, high degree of single photon purity, indistinguishability, and entanglement still impedes the practical applications. Semiconductor quantum dots are one of the leading system that have exhibited their potential for on-demand generation of high-quality single and entangled photon pairs for above applications. In this work, epitaxially grown III-V semiconductor quantum dots are investigated for driving their application in future quantum networks. First, an individual quantum dot emitting two pairs of entangled photons under pulsed two-photon resonant excitation has been utilized for realization of entanglement swapping, with the swapped photon pairs yielding a fidelity of 0.81 ± 0.04 to the Bell state Ψ+. To explore the practical limits of future quantum networks featuring multiple semiconductor based sources, we scrutinize the consequences of device fabrication, dynamic tuning techniques, time evolution of entanglement, and statistical effects on two separated quantum dot devices adapted in an entanglement swapping scheme. A numerical model based on the observed experimental data is proposed, serving not only as a benchmark for scalability of quantum dot devices, but also laying a roadmap for optimization of solid-state quantum emitters in quantum networks. For real-world quantum applications envisioned with quantum dots, the brightness of the quantum light sources is one of the key enabling factors, which is determined by the source excitation and extraction efficiency, as well as system detection system efficiency. Usually, the primary issue restricting the extraction of photons from III-V semiconductor quantum dots is the high-refractive index material of the host matrix which causes at the semiconductor-vacuum interface. To improve the photon extraction efficiency, a simple and efficient structure based on the principle of optical antennas is developed, resulting in an observed extraction of 17% of single photons in the telecom O-band, and a broadband enhancement of up to 180 times compared to the as-grown sample. A further limiting factor in the source efficiency is caused by the presence of charges in the solid-state environment. Charge fluctuation occur that quench radiative emission processes in resonant excitation schemes and induce fluorescence intermittence (blinking) that deteriorates the quantum yield. The photo-neutralization of GaAs/AlGaAs quantum dots excited by two-photon resonant pumping is investigated. Applying weak gate laser light to the quantum dot allows for controlling the charges capture processes. By adjusting the gate laser power and wavelength, an increase in excitation efficiency of 30% is observed compared to the two-photon resonant excitation without optical gating. The transition rates between the neutral and charged ground state are investigated by means of auto-/cross- correlation measurements. Furthermore, by studying a series of surface-passivated samples with different dot-to-surface distance as close to 20 nm, ODT was found to be an effective compound to neutralize the surface states, leading to reduced formation of non-radiative transition channels. It is anticipated that such a passivation method paves the way of near-field coupling related nano-photonic devices, or elimination of surface states for well-preserved emission properties towards the development of uncapped structure, fundamentally getting rid of total internal reflection to the maximum extent.European Research Council (ERC)/Starting Grant/QD-NOMS/E

Design And Construction Of A Robotic Vehicle To Assist During Planetary Surface Operations

In the near future, astronauts will explore new planetary surfaces in the Solar System. To enable peak performance, these astronauts will need to utilize all of the tools at their disposal. It is proposed that one such tool is a planetary surface rover designed specifically to assist the astronauts during their Extra-Vehicular-Activities (EVA’s). This rover is designed and built to operate in concert with existing analog planetary surface infrastructure at the University of North Dakota (UND). This rover will be remotely controlled by an astronaut located on the planetary surface, enabling real-time operation and obstacle avoidance. The rover will act primarily as a relay for audio and video communications between the astronauts in the field and the Inflatable Lunar Habitat (ILH), or another planetary outpost. This rover will be designed to enable storage for tools and samples, freeing the astronauts from the tedious and physically demanding task of carrying items for long distances encumbered by an EVA suit. This thesis will describe the design of the rover and the rationale for each design decision. Upon completion of the rover, this thesis will report on the real-world performance of the rover, the effectiveness of the subsystems, and the lessons learned as a result of initial testing. Using the rover and the information obtained from this thesis, future astronaut-rover interaction studies will be conducted that will be important to the future of human planetary exploration