Seismic or wavefield interferometry refers to a set of methods that synthesize wavefields between pairs of receivers, pairs of sources, or a source and a receiver, using wavefields propagating from and to surrounding boundaries of sources and/or receivers. Starting from cross-correlations of ambient seismic noise recordings, which provide the signal between two receivers as if one of them had been an active source, interferometric methods developed rapidly within the last decade, revolutionizing the way in which seismic, acoustic, elastic, or electromagnetic waves are used to image and monitor the interior of a medium. Only recently, an explicit link was found between the methods of source-receiver interferometry (SRI) and seismic imaging, a technique widely used in seismic exploration to map diffractors and reflectors in the subsurface, but also in more academic studies investigating, for example, deep crustal processes. This link is particularly interesting because SRI, in contrast to classical imaging schemes, does not rely on the single-scattering assumption but accounts for all multiple-scattering effects in the medium. While first non-linear imaging schemes based on SRI have been proposed, the full potential of the method remains to be explored and a number of open questions concerning, for example, the role of non-physical energy in interferometric wavefield estimates, require further investigation. The aim of this thesis is to gain more insight into the method of source-receiver interferometry in the context of wavefield construction and analysis in multiply scattering media, especially when theoretical requirements of the method (such as complete boundaries of sources and receivers, surrounding the medium of interest) are not met. First I analyse the single diffractor case using partial surface boundaries only. I find that only two out of eight terms of the SRI equation are required to construct a robust estimate of the scattered wavefield, and that one of these two terms is also used in seismic imaging. The other term provides a pseudo-physical estimate of the scattered wave; this is a new type of non-physical energy that emulates the kinematics of a physically scattered wave. I then proceed to a multiple scattering scenario, using the pseudo-physical term to predict the travel times and exact scattering paths of multiply diffracted waves. The presented algorithm is purely data-driven and fully automated and, as a by-product, provides a new tool to isolate primary diffracted waves from a complex multiply diffracted wavefield. Finally, the concept is expanded to multiply reflecting media. In reflection seismic data, multiply reflected waves should be removed prior to migration in order to avoid artefacts in the seismic image. I demonstrate how internal multiples can be estimated and attenuated using pseudo-physical energy constructed from SRI. Moreover, an explicit link is derived between the internal-multiple equation based on SRI and the internal-multiple equation derived from the inverse-scattering series (ISS), currently the most capable algorithm for internal-multiple attenuation. Using the insight provided by the SRI approach, I suggest an alternative equation that estimates internal multiples more effciently compared to the current method. Overall, this thesis improves our understanding of how physical, non-physical, and pseudo-physical wavefields are constructed in SRI, how new information about multiply scattered wavefields can be inferred, and how SRI relates to other methods of wavefield analysis, in particular seismic imaging and the ISS.

This Dissertation describes how I used a three nanograting Mach-Zehnder atom beam interferometer to precisely measure a wavelength of light, known as a tune-out wavelength, that causes zero energy shift for an atom. I also describe how such measurements can be remarkably sensitive to rotation rates. It is well known that atom interferometry can be used to measure accelerations and rotations, but it was a surprise to find out that tune-out wavelength measurements can under certain conditions be used to report the absolute rotation rate of the laboratory with respect to an inertial frame of reference. I also describe how we created conditions which improve the accuracy of tune out wavelength measurements. These measurements are important because they serve as a benchmark test for atomic structure calculations of line strengths, oscillator strengths, and dipole matrix elements. I present a new measurement of the longest tune-out wavelength in potassium, λzero = 768.9701(4) nm. To reach sub-picometer precision, an optical cavity surrounding the atom beam paths of the interferometer was used. Although this improved the precision of our experiment by increasing the light-induced phase shifts, the cavity also brought several systematic errors to our attentions. For example, I found that large ±200 pm shifts in tune-out wavelengths can occur due to the Earth's rotation rate. To solve this problem, I demonstrated that controlling the optical polarization, the magnetic field, and the atom beam velocity distribution can either suppress or enhance these systematic shifts. Suppressing these systemic shifts in tune-out wavelengths is useful for precision measurements used to test atomic structure calculations. By enhancing these systematic shifts, the interferometer can be a gyroscope that utilizes tune-out wavelengths.

M.Ing. / Bragg gratings are important components for sensing and for wavelength-division multiplexed optical communication systems. These gratings are manufactured by either side-writing of the fiber with a high intensity UV light through a phase mask, or by exposing the fiber to interference fringes through an interferometer arrangement. With one phase mask, only a small range of grating wavelengths is possible. This is achieved by pre-straining the fiber during the writing process. The limitation arises from the break strength of the fi ber, allowing a maximum range of Bragg wavelengths of only approximately 10 nm. The interferometric technique uses a beam splitter to divide a single input UV beam into two and intersecting them at the fiber. The angle at which the beams intersect will determine the period of the interference fringes and thus the Bragg grating written in the optical fiber. The Argon-ion laser is used with a 1060 nm phase mask (used to split beam) to write Bragg gratings with reflections from 1012 to 1600 nm. Three accurate- translation and rotation stages are used to keep the fiber at the beam intersection. Alignment, mechanical stability and coherence of laser are critical.

This thesis reports the calibration, imaging and analysis of one epoch of VLBI observations of the v (italics) = J (italics) = 1-0 transition of SiO towards VY CMa. Full polarisation information was recorded, allowing high resolution synthesis maps of each of the four Stokes parameters to be produced. A total of 81 maser components were extracted from the total intensity map, each approximately 1 mas in size. The emission spans approximately 100 x 80 mas in right ascension and declination and is concentrated to the east. The maser component positions were fitted to a ring of radius ~ 3.2R₊ (italics), or 7.2 x 1O¹⁴ cm for a stellar distance of 1.5 kpc. If the stellar position is assumed to be the centre of this ring then almost all of the maser components fall within the inner dust shell radius, which is at ~ 5R (italics)ϰ All of the maser components fall between 1.5R (italics)ϰ and 6R (italics)ϰ. A velocity gradient with position angle was observed in the sparsely filled western region of the maser ring. If interpreted as evidence of shell rotation, this gradient implies a rotational velocity of v (italics) rot (subscirpt) sin i (italics) = 18 km.s⁻¹. The fractional circular and linear polarisations of the maser spots were derived from the Stokes parameter maps. The mean fractional circular polarisation of the masers components was ~ 2 percent and the median fractional linear polarisation was ~ 6 percent, with many spots displaying over ~ 30 percent linear polarisation. The mean circular polarisation implies a magnetic field of ~ 4 G in the SiO maser region if the polarisation is due to Zeeman splitting. Two maser components display a rotation of linear polarisation position angle with velocity, possibly implying a connection between the magnetic field and the velocity field variations in the region of these components.

Les systèmes planétaires sont nés du gaz et de la poussière des disques circumstellaires autour des étoiles jeunes. Pour comprendre comment les systèmes planétaires se forment, une connaissance détaillée de la structure et de l'évolution de ces disques est requise. Bien que, cela soit presque bien compris pour les régions des disques observés à des échelles spatiales de plusieurs unités astronomiques, la structure de ces disques explorés à l'échelle de quelques unités astronomiques et surtout à moins d'une unité astronomique reste une énigme. Au cours de ces dernières années, il est devenu possible de directement résoudre spatialement la région interne des disques protoplanétaires avec les techniques d'interférométrie optiques. L'objectif de cette thèse est une étude multi-longueur d'onde de l'évolution des disques protoplanétaires en déterminant leur distribution de densité et de température, leur taille, la composition de la poussière et aussi la cinématique du gaz. J’ai construit ma thèse en étudiant trois domaines de longueurs d'onde complémentaires: étude de la photosphère de l'étoile et de son disque gazeux à proximité par le biais de l'interférométrie visible, étude de la structure radiale et verticale du bord interne d'un disque de pré-transition à des fractions d'unité astronomique en interférométrie proche infra-rouge, et la caractérisation des régions des disques situées à quelques unités astronomiques de l'étoile centrale, au travers de la spectroscopie et de l'interférométrie infra-rouge moyen / Planetary systems are born in circumstellar gas and dust disks surrounding Young Stellar Objects (YSOs). To understand how planetary systems form, a detailed knowledge of the structure and evolution of these disks is required. Although, this is almost well understood for the regions of the disks observed with a spatial resolution of several AUs, the structure of these disks probed at a few AU scale and especially inward of 1 AU remains a puzzle. In recent years, it has become possible to directly spatially resolve the inner region of protoplanetary disks with optical interferometry technique. The context of this thesis is a multi-wavelength investigation of the protoplanetary disks evolution by determining their density distribution, their temperature distribution, the size and com- position of the dust components and finally the kinematics of the gas. I have developed my thesis following three complementary wavelength domains: study of the photosphere of the star and its nearby gaseous disk through visible interferometry, study of the radial and vertical structure of the inner rim of a pre-transitional disk at fractions of an AU through near-IR interferometry, and, the characterization of the disk regions at a few AUs from the central star through spectroscopic and mid-IR interferometry. To analyse the visible-, near- and mid-IR interferometric observations, I have focused my attention on three well known sources, 51 OPh, HD 100546 and MWC 480 respectively that they have not been observed in these wavelengths.

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The diagnostic and pharmaceutical industries rely on tools for characterizing, discovering, and developing bio-molecular interactions. Diagnostic assays require high affinity capture probes and binding specificity for accurate detection of biomarkers. Selection of drug candidates depends on the drug residency time and duration of drug action. Further, biologic drugs can induce anti-drug antibodies, which require characterization to determine the impact on the drug safety and efficacy. Label-free biosensors are an attractive solution for analyzing these and other bio-molecular interactions because they provide information based on the characteristics of the molecules themselves, without disturbing the native biological systems by labeling. While label-free biosensors can analyze a broad range of analytes, small molecular weight analytes (molecular weight < 1kDa) are the most challenging. Affinity measurements for small molecular weight targets require high sensitivity and long-term signal stability. Additional difficulties occur with different liquid refractive indices that result from to temperature, composition, or matrix effects of sensor surfaces. Some solutions utitlize strong solvents to increase the solubility of small molecules, which also alter the refractive index. Moreover, diagnostics require affinity measurements in relevant solutions, of various refractive indices. When a refractive index difference exists between the analyte solution and the wash buffer, a background signal is generated, referred to as the bulk effect, obscuring the small signal due to surface binding in the presence of large fluctuations due to variations of the optical refractive index of the solutions. The signal generated by low molecular weight analytes is small, and conventional wisdom tends toward signal amplification or resonance for detection of these small signals. With this approach, Surface Plasmon Resonance (SPR) has become the gold standard in affinity measurement technologies. SPR is an expensive and complex technology that is highly susceptible to the bulk effect. SPR uses a reference channel to correct for the bulk effect in post-processing, which requires high precision and sophisticated temperature control, further increasing the cost and complexity. Additionally, multiplexing is desirable as it allows for simultaneous measurements of multiple ligands; however, multiplexing is only possible in the imaging modality of SPR, which has lower sensitivity and difficulty with referencing. The Interferometric Reflectance Imaging Sensor (IRIS) is a low-cost, optical label-free bio-molecular interaction analysis technology capable of providing precise binding affinity measurements; however, limitations in sensitivity and usability have previously prevented its widespread adaptation. Overcoming these limitations requires the implementation of automation, compact and easy-to-use instrumentation, and increased sensitivity. Here, we explore methods for improved sensitivity and usability. We achieve noise reduction and elimination of solution artifacts (bulk effect) through engineered illumination uniformity and temporal and spatial image processing. To validate these methods, we experimentally analyze small molecule molecular interactions to demonstrate highly sensitive kinetic binding measurements, independent of solution refractive index. / 2023-09-24T00:00:00Z

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No description available.

Optical-based techniques have found merit in measuring displacement and strain for decades. These techniques are commonly used in numerous applications ranging from large displacements in wind tunnel experiments to displacement measurements on the submicron scale. Projection Moiré Interferometry (PMI) is an out-of-plane displacement measurement technique, and consists of capturing reference and deformed images of a grid pattern projected on the test object. By differencing the reference and deformed images of the projected grid pattern, a fringe pattern is generated from which the displacement field can be extracted. This computation requires calibration procedures that analyze a number of fringe patterns from known displacements to compute the fringe sensitivity constant (FSC) values. This process can be time consuming and for large-scale applications, very costly. In addition, due to the projection-oriented nature of this technique, measuring displacements in applications with non-viewable, hidden, or inaccessible reference surfaces excludes the use of PMI. In this thesis, a technique is developed which eliminates calibration procedures through implementation of virtual calibration methods, and typical PMI measurement processes are extended to include digital reference images in determining displacements from inaccessible surfaces. Using camera calibration routines and ray tracing techniques, each major component of the PMI arrangement is modeled as virtual components within a computer simulation where the entire calibration process can be performed. A CAD model of the inaccessible surface is then converted to a point cloud and a surface interpolation function is implemented to generate a displacement field, which can be correlated and differenced from the displacement field of the actual object. Many potential applications exist in the automobile, aerospace, and other manufacturing industries. These industries provide numerous large-scale applications where conventional calibration is not cost-effective. In addition, these applications provide instances where differences between the deformed and reference images represent the manufacturing errors due to dimensional variations and assembly processes. An automated, self-calibrating, whole-field projection measuring system would greatly increase inspection efficiency of large production parts and final assemblies. It is in these types of circumstances that the developed techniques would be of most use.