Study of conceptual deep space monitor communications systems using a single earth satellite. Volume III - Appendix Final report

Condensed technical survey for deep space monitor communications system using earth satellit

Calibration of planetary brightness temperature spectra at near-millimeter and submillimeter wavelengths with a Fourier-transform spectrometer

A medium-resolution Fourier-transform spectrometer for ground-based observation of astronomical sources at near-millimeter and submillimeter wavelengths is described. The steps involved in measuring and calibrating astronomical spectra are elaborated. The spectrometer is well suited to planetary spectroscopy, and initial measurements of the intrinsic brightness temperature spectra of Uranus and Neptune at wavelengths of 1.0 to 1.5 mm are presented

Femtosecond lasers for datacommunications applications

The work presented in this thesis details the development of all-solid-state ultrashort pulsed lasers suitable for datacommunications applications at either 1300nm or 1550nm. This is achieved through the design and construction of three different types of laser system based on the gain materials Cr⁴⁺:forsterite (chromium-doped magnesium iron silicate) and Cr⁴⁺:YAG (chromium-doped yttrium aluminium garnet). A Cr⁴⁺:forsterite based system is the first laser that is presented. This configuration utilises a relatively novel GalnNAs semiconductor device to initiate the generation of 130fs pulses around 1300nm. Although GalnNAs devices have previously been used to generate pulses of light in the picosecond domain, this is the first time ultrashort pulses have been achieved in the femtosecond domain. As such, it has been possible to use the results from this laser system to further the understanding of various dynamics of GalnNAs devices. An SBR mode-locked Cr⁴⁺:YAG laser system introduces the concept of Femtosecond pulse generation around 1550nm. This is done in order to lay the necessary foundations for understanding the motivation and physics behind high pulse repetition frequency (prf) all-solid state femtosecond lasers suitable for datacommunications applications. Details are then given for the construction and operation of a simple 3-element Cr⁴⁺:YAG laser that generates 70fs pulses at a prf greater than 4GHz. The success of this system leads to the development of a compact and robust engineered prototype with a footprint of 215x 106mm². Integration of the high prf laser systems into novel optical time division multiplexing/wavelength division multiplexing (OTDM/WDM) based assessments prove successful with the demonstration of a datacommunications system capable of generating 1.36Tb/s. This still remains to be the only system capable of achieving such a high capacity from a single source and demonstrates the ongoing success of femtosecond lasers through continued research and development

Interaction between light and highly confined hypersound in a silicon photonic nanowire

In the past decade there has been a surge in research at the boundary between photonics and phononics. Most efforts have centred on coupling light to motion in a high-quality optical cavity, typically geared towards manipulating the quantum state of a mechanical oscillator. It was recently predicted that the strength of the light-sound interaction would increase drastically in nanoscale silicon photonic wires. Here we demonstrate, for the first time, such a giant overlap between near-infrared light and gigahertz sound co-localized in a small-core silicon wire. The wire is supported by a tiny pillar to block the path for external phonon leakage, trapping 10 GHz phonons in an area of less than 0.1 mu m(2). Because our geometry can also be studied in microcavities, it paves the way for complete fusion between the fields of cavity optomechanics and Brillouin scattering. The results bode well for the realization of optically driven lasers/sasers, isolators and comb generators on a densely integrated silicon chip

On the advancement of core/shell titanium dioxide nanomaterials for microwave absorption

Title from PDF of title page viewed May 21, 2020Dissertation advisor: Xiaobo ChenVitaIncludes bibliographical references (pages 139-160)Thesis (Ph.D.)--Department of Chemistry and Department of Geosciences. University of Missouri--Kansas City, 2020Controlling the interactions between incident electromagnetic energy and matter is of critical importance for many civil and military applications, such as photocatalysis, solar cells, optics, radar detection, communications, information processing and transport, et al. For interactions in the microwave region of the electromagnetic spectrum, the generation of materials which have desirable dielectric and magnetic properties is critical, as these properties ultimately determine how a material system interacts with these incident electromagnetic waves. In this dissertation, we present a comprehensive report of the microwave absorption properties of metal/hydrogen treated anatase titanium dioxide nanoparticles, where the synergistic treatment induces favorable structural, optical, and microwave absorption properties, which can be fine-tuned via controlling the temperature of materials treatment. Furthermore, this material demonstrates strong reflection loss and effective bandwidth properties, which places its performance within the top quintile of all materials produced. The high efficiency of microwave absorption is likely linked to the disordering-induced property changes in the materials. Along with the increased microwave absorption properties are largely increased visible-light and IR absorptions, and enhanced electrical conductivity and reduced skin-depth, which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the metal/hydrogen treatment.Introduction -- Proposal -- Methods -- Aluminum/hydrogen treated titanium dioxide nanoparticles -- Magnesium/hydrogen treated titanium dioxide nanoparticles -- Closing remarks -- Appendix A. Supplemental figures -- Appendix B. Softwar

Light-Sound Interaction in Nanoscale Silicon Waveguides

This thesis studies the interaction between near-infrared light and gigahertz sound in nanoscale silicon waveguides. Chapter 2 introduces photon-phonon coupling and its theoretical description, describing basic mechanisms and developing a quantum field theory of the process. Chapter 3 explores the dynamical effects in both waveguides and cavities. It also proves a connection between the Brillouin gain coefficient and the vacuum coupling rate. Chapter 4 deals with the observation of Brillouin scattering in nanoscale silicon waveguides. The waveguides tightly confine $193 \, \text{THz}$ light and $10 \, \text{GHz}$ acoustic vibrations. The acoustic quality factor remains limited to about $300$ because of leakage into silica substrate. These waveguides are optically transparent in a narrow band of frequencies at a pump power of $25 \, \text{mW}$. Besides this amplification, we translate a $10 \, \text{GHz}$ microwave signal across $1 \, \text{THz}$. Chapter 5 extends the experimental work of chapter 4 by fabricating a cascade of fully suspended nanowires held by silica anchors. This enhances the mechanical quality factor from $300$ to $1000$, enabling the observation of Brillouin amplification exceeding the propagation losses in silicon. The amount of amplification is mostly limited by a rapid drop in acoustic quality as the number of suspensions increases. We propose a mechanism to cancel this inhomogeneous broadening. Chapter 6 looks at the potential of narrow silicon slot waveguides to enhance the optomechanical coupling. For certain dimensions, these waveguides support opto-acoustic modes with an interaction efficiency simulated an order of magnitude above those of single-nanobeam systems.Comment: PhD thesis defended at Ghent Universit

Time-Domain Channel Estimation for Extremely Large MIMO THz Communications with Beam Squint

In this paper, we study the problem of extremely large (XL) multiple-input multiple-output (MIMO) channel estimation in the Terahertz (THz) frequency band, considering the presence of propagation delays across the entire array apertures, which leads to frequency selectivity, a problem known as beam squint. Multi-carrier transmission schemes which are usually deployed to address this problem, suffer from high peak-to-average power ratio, which is specifically dominant in THz communications where low transmit power is realized. Diverging from the usual approach, we devise a novel channel estimation problem formulation in the time domain for single-carrier (SC) modulation, which favors transmissions in THz, and incorporate the beam-squint effect in a sparse vector recovery problem that is solved via sparse optimization tools. In particular, the beam squint and the sparse MIMO channel are jointly tracked by using an alternating minimization approach that decomposes the two estimation problems. The presented performance evaluation results validate that the proposed SC technique exhibits superior performance than the conventional one as well as than state-of-the-art multi-carrier approaches