Microwave holography is a well established method of using the Fourier relationship between an antenna’s current distribution and its complex beam-pattern to produce surface maps of large parabolic antennas. As the final part of a surface upgrade, a holographic map of the HartRAO 26 m telescope was produced. This showed that the surface has an RMS error of 0.45 mm. The measurement used a small reference dish to correlate against and retrieve amplitude and phase values. Due to system phase instabilities, this dish had to be attached to the measured antenna in order to enable sharing a high frequency local oscillator (LO). The movement was modelled and corrected for. However, a slight distortion remained. It is recommended that, either the LO distribution system is stabilised by using multiple PLLs or amplifiers and low loss cables are used to enable moving the reference antenna to a stationary position.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 09 February 2016. / The main goal of this dissertation is to construct a better understanding of the subtleties that arise in the holographic computation of extremal correlators. It is well known that these computations, in the gravitational description, su er from divergences, but the interpretation and origin of these divergences is unclear. The study starts with detailed computations of two- and three-point functions of a scalar eld minimally coupled to gravity on Euclidean AdSd space, three-point functions of two giant gravitons and one light graviton, and three-point functions of the Kaluza-Klein gravitons, using supergravity theory. Further, we also give the computation of these same correlators in the dual CFT. These involve novel techniques in the matrix model, including methods that employ Schur polynomials in the dual gauge theory analysis. By employing the usual AdS=CFT dictionary, we argue that extremal correlators are naturally related to collinear particles. There are divergences that arise in collinear amplitudes as a consequence of the fact that the particles momenta are parallel. We therefore reach the suggestive idea that the divergences in extremal correlator computations are linked to collinear divergences. Much remains to be done to really establish this connection. / LG2018

Title also in Chinese. / Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 92-93.

Chan Tak Shun = 摻鐵鈮酸鋰晶體中相位相關的亮光生伏打空間孤子的相互作用的觀察及光生伏打媒介中高調制深度下所寫的光折變全息圖的理論研究 / 陳德信. / Thesis submitted in: July 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 115-116). / Abstracts in English and Chinese. / Chan Tak Shun = Shan tie ni suan li jing ti zhong xiang wei xiang guan de liang guang sheng fu da kong jian gu zi de xiang hu zuo yong de guan cha ji guang sheng fu da mei jie zhong gao diao zhi shen du xia suo xie de guang zhe bian quan xi tu de li lun yan jiu / Chen Dexin. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / References --- p.9 / Chapter Chapter 2 --- Background --- p.10 / Chapter 2.1 --- Space-Charge Field and Band Transport Model --- p.10 / Chapter 2.2 --- Photorefractive Effect and Nonlinear Wave Equation --- p.24 / Chapter 2.3 --- Two-Wave Mixing and Diffraction of Light Incident onto an Index Grating --- p.34 / Chapter 2.4 --- Photorefractive Spatial Solitons --- p.48 / References --- p.60 / Chapter Chapter 3 --- Relevance of interpretation of experimental results of interactions of optical spatial solitons and interaction geometry --- p.62 / Chapter 3.1 --- Introduction --- p.62 / Chapter 3.2 --- Theoretical Model --- p.63 / Chapter 3.3 --- Results and Discussion --- p.65 / Chapter 3.4 --- Conclusions --- p.71 / References --- p.72 / Chapter Chapter 4 --- Experimental investigation of phase-dependent interactions of photovoltaic bright spatial solitons in photorefractive Fe:LiNb03 --- p.75 / Chapter 4.1 --- Introduction --- p.75 / Chapter 4.2 --- Theoretical Background --- p.76 / Chapter 4.3 --- Experiment --- p.83 / Chapter 4.4 --- Results and Discussion --- p.86 / Chapter 4.5 --- Conclusions --- p.90 / References --- p.91 / Chapter Chapter 5 --- Photorefractive hologram writing with high modulation depth in photovoltaic media under different boundary conditions --- p.94 / Chapter 5.1 --- Introduction --- p.94 / Chapter 5.2 --- Theoretical Model and Method --- p.97 / Chapter 5.3 --- Results and Discussion --- p.99 / Chapter 5.4 --- Conclusions --- p.114 / References --- p.115 / Chapter Chapter 6 --- Conclusions and future outlook --- p.117

Thesis (M.S.V.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references (leaf 34). / by Donald Karl Thornton. / M.S.V.S.

Diffractive optical elements (DOEs) are thin, light-weight devices capable of shaping light both spatially and spectrally. Classical light is a multivariate vector field: at each wavelength and at each point in space, it is characterized an amplitude and phase for two orthogonal polarizations. “Metasurfaces” are a class of DOEs composed of subwavelength structures engineered to alter a featureless wavefront into a custom wavefront; a multivariate metasurface may control several parameters simultaneously and independently. If limited to low-loss dielectric materials, metasurfaces promise functionalities and efficiencies unparalleled in other DOEs, and are manufacturable by mature micro- and nanofabrication methods. Here, we expand the capabilities of metasurfaces to generate multivariate wavefronts. By engineering both the phase and the phase dispersion, we experimentally demonstrate metasurfaces focusing light to a single point independently of wavelength or polarization. By tuning the structural birefringence and in-plane orientation angle of rectangular nanostructures, we experimentally demonstrate arbitrary control of both phase and amplitude, enabling holography as it was originally envisioned. By maximizing the in-plane Bragg scattering of a Photonic Crystal Slab, and then successively adding symmetry-breaking perturbations to the otherwise perfect lattice, we may control angular dependence, optical lifetime, and polarization dependence of up to four optical resonances simultaneously and independently (which we study using Group Theory and fullwave simulations). By spatially varying the perturbations, the wavefronts at the resonance frequencies may be spatially tailored while the non-resonant frequencies are unaffected, promising DOEs uniquely suitable for augmented reality applications.

No description available.

Rainbow holography is the medium I have chosen to specialize in. Holography itself uses light as a sculptural element. In regards to my work, rainbow holography stresses the field of experimentation with the light spectrum until a certain point that I define as travelling the superhighway from reality to virtual worlds. My work appears then as the documentation, in the form of rainbow holograms, of this travel. It depicts narrative imagery while capturing the moments I existed in this virtual world set behind the rainbow. This project aims to present through still, 3D and filmic imagery the co ??? existence of the physical body and its psychological realm. The psychological reality is articulated as a fictional landscape and the rainbow is used as a metaphor for travel between real and virtual worlds. More importantly, I see holography or rainbow holography as a means of crystallising the vision of the unreachable world behind the rainbow. I see my practice as a new way of using this medium by using this rainbow world as subject matter within the rainbow hologram. By experimenting with combined image processing techniques within rainbow holography, such as analogue white light transmission holograms, full colour digital stereograms, and dot matrix holograms, it becomes possible to generate a synthetic new world. Here each pixel can have the potential to be every color of the rainbow spectrum simultaneously, depending on the angle of the eye of the perceiver. It is here that my investigation through holographic representation has led me to explore and create other worldly landscapes and to extend reality. Our longing to travel over the rainbow into our imagination is with us from a very young age. For me this desire has lasted well into adulthood and has somehow found itself at the centre of my creations over the last few years. The childlike and na??ve appearance of my imagery has the ability to evoke the feeling in the viewers of the nostalgia they may have felt as a child, when confronted with the intense experience and wonder of the imaginings of the rainbow. My work trades on a misunderstanding that the medium of holography is taken as a direct representation of an existing reality. My first hologram I???m a rainbow depicts an alter-egotistical projection of myself as a rainbow princess living in a far away fairytale rainbow galaxy, and communicating with earth beings via the technology of the message contained within the hologram. The hologram has often been associated in science fiction with a message to save the planet. This body of work invites viewers to delve into the depths of their imagination, to save this place where I have travelled by believing in it. As in the story of peter pan where the children are asked to clap their hands if they believe in fairies, by others believing in my imagination they are able to save it. The world within the imagination holds no fixed place; it is a shifting and dynamic space. This quality is shared with the rainbow, which is similarly ephemeral, vanishing and appearing within the eye of the beholder according to weather patterns. The rainbow hologram is a fixed rainbow. When replayed through the eyes of the viewer, the interaction with the real rainbow is recalled, and the viewer enters into the imagination to perceive the work. Throughout this paper I have referred to concepts and techniques in other fields such as physics, anthropology, art history and theory. My research is by no means intended as primarily a technical examination of the medium of rainbow holography. The holographic environments I have made rearrange elements from the real world with fictitious realities. They make people feel as if they are viewing a world that is real, but which imitates unreal ideas. These holographic environments enable viewers to experience ideas as a real place. As Rainbow holography is a relatively new medium, and as my own work uses the rainbow as a multi-layered tool I feel it necessary to investigate the appearance of the rainbow in nature and the reaction of humans to the rainbow as a mythical component in ancient cultures. I am interested in investigating how the rainbow has been used a metaphor for travelling from a material world to ???other worlds??? through its presence in various imaging processes through specific art works. The different ways the rainbow has been used have enabled me to more accurately understand my own work as being a nexus between depicting and generating rainbows. Furthermore, in the discussion of the application of rainbow holography I can show that my own work is necessarily different because of the way I am depicting a rainbow to explore undiscovered territory in which I am the author. Finally I look at how holography is perceived by the public, which helps me to explain the way in which my own work is perceived. Deliberately using the idea of an image in its surrounding context has helped to achieve my desired outcome: to make people believe that the world behind the rainbow really does exist and that I have travelled there, and that they too can do so via viewing my work.

xii, 207 leaves : ill., photos., graphs, tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1979) from the Dept. of Mechanical Engineering, University of Adelaide

Rainbow holography is the medium I have chosen to specialize in. Holography itself uses light as a sculptural element. In regards to my work, rainbow holography stresses the field of experimentation with the light spectrum until a certain point that I define as travelling the superhighway from reality to virtual worlds. My work appears then as the documentation, in the form of rainbow holograms, of this travel. It depicts narrative imagery while capturing the moments I existed in this virtual world set behind the rainbow. This project aims to present through still, 3D and filmic imagery the co ??? existence of the physical body and its psychological realm. The psychological reality is articulated as a fictional landscape and the rainbow is used as a metaphor for travel between real and virtual worlds. More importantly, I see holography or rainbow holography as a means of crystallising the vision of the unreachable world behind the rainbow. I see my practice as a new way of using this medium by using this rainbow world as subject matter within the rainbow hologram. By experimenting with combined image processing techniques within rainbow holography, such as analogue white light transmission holograms, full colour digital stereograms, and dot matrix holograms, it becomes possible to generate a synthetic new world. Here each pixel can have the potential to be every color of the rainbow spectrum simultaneously, depending on the angle of the eye of the perceiver. It is here that my investigation through holographic representation has led me to explore and create other worldly landscapes and to extend reality. Our longing to travel over the rainbow into our imagination is with us from a very young age. For me this desire has lasted well into adulthood and has somehow found itself at the centre of my creations over the last few years. The childlike and na??ve appearance of my imagery has the ability to evoke the feeling in the viewers of the nostalgia they may have felt as a child, when confronted with the intense experience and wonder of the imaginings of the rainbow. My work trades on a misunderstanding that the medium of holography is taken as a direct representation of an existing reality. My first hologram I???m a rainbow depicts an alter-egotistical projection of myself as a rainbow princess living in a far away fairytale rainbow galaxy, and communicating with earth beings via the technology of the message contained within the hologram. The hologram has often been associated in science fiction with a message to save the planet. This body of work invites viewers to delve into the depths of their imagination, to save this place where I have travelled by believing in it. As in the story of peter pan where the children are asked to clap their hands if they believe in fairies, by others believing in my imagination they are able to save it. The world within the imagination holds no fixed place; it is a shifting and dynamic space. This quality is shared with the rainbow, which is similarly ephemeral, vanishing and appearing within the eye of the beholder according to weather patterns. The rainbow hologram is a fixed rainbow. When replayed through the eyes of the viewer, the interaction with the real rainbow is recalled, and the viewer enters into the imagination to perceive the work. Throughout this paper I have referred to concepts and techniques in other fields such as physics, anthropology, art history and theory. My research is by no means intended as primarily a technical examination of the medium of rainbow holography. The holographic environments I have made rearrange elements from the real world with fictitious realities. They make people feel as if they are viewing a world that is real, but which imitates unreal ideas. These holographic environments enable viewers to experience ideas as a real place. As Rainbow holography is a relatively new medium, and as my own work uses the rainbow as a multi-layered tool I feel it necessary to investigate the appearance of the rainbow in nature and the reaction of humans to the rainbow as a mythical component in ancient cultures. I am interested in investigating how the rainbow has been used a metaphor for travelling from a material world to ???other worlds??? through its presence in various imaging processes through specific art works. The different ways the rainbow has been used have enabled me to more accurately understand my own work as being a nexus between depicting and generating rainbows. Furthermore, in the discussion of the application of rainbow holography I can show that my own work is necessarily different because of the way I am depicting a rainbow to explore undiscovered territory in which I am the author. Finally I look at how holography is perceived by the public, which helps me to explain the way in which my own work is perceived. Deliberately using the idea of an image in its surrounding context has helped to achieve my desired outcome: to make people believe that the world behind the rainbow really does exist and that I have travelled there, and that they too can do so via viewing my work.