In many applications such as beam shaping, mode conversion, and phase encoding it is necessary to alter the spatial phase profile of a beam via a phase mask. Conventional techniques to accomplish this either involve surface relief profiling in thin films such as PMMA or refractive index modulation in bulk photorefractive crystals such as lithium niobate. These materials have been used extensively for the past several decades and perform admirably in low power conditions. However, in high power systems these materials will be destroyed, requiring a new means of producing phase masks. In this dissertation a method for producing robust phase masks in the bulk of photo-thermo-refractive glass is developed and successfully demonstrated. Three main applications of phase masks were studied in detail. The first is mode conversion, where binary phase masks convert a Gaussian beam to higher order modes. The second is beam shaping, where phase masks are used as focusing elements and for optical vortex generation. Near-theoretical conversion efficiency was achieved for all elements in these cases. The third application is aberration analysis and correction. Here the degradation of volume Bragg gratings recorded in an aberrated holographic system was modeled, with the simulations indicating that correcting elements are generally necessary for high-quality production of gratings. Corrective phase masks are designed which can selectively correct one or multiple aberrations of varying magnitudes are shown. A new type of optical element is also developed in which a phase mask is encoded into a transmitting Bragg grating. This technique combines the local phase modulation of a phase mask with the multiplexing ability of transmitting Bragg gratings, allowing for multiple phase masks to be recorded in a single element. These masks may be used at any wavelength iii satisfying the Bragg condition, increasing the useful wavelength regime of a single element by orders of magnitude.

<p>Biodynamic imaging (BDI) is a high-content optical imaging technology based on Fourier-domain digital holography and Doppler spectroscopy of intracellular dynamics. There are three main functions of the BDI technique, which are optical coherence imaging (OCI), motility contrast imaging (MCI) and tissue dynamics spectroscopy (TDS). OCI is related to <em>en face</em> optical coherence tomography (OCT) using partially coherent speckle generated by broad-area illumination with coherence detection through digital holography. MCI provides noninvasive functional imaging by treating intracellular motility as an endogenous dynamic imaging contrast agent. TDS produces broad-band Doppler fluctuation power spectra that contain the ensemble of all intracellular motions by collecting and extracting depth-resolved quasi-elastic dynamic light scattering from inside multicellular living tissue. This thesis presents the development and applications of BDI systems. Doppler spectral clustering analysis is demonstrated when comparing fresh canine lymphoma biopsies and their corresponding flash-Frozen samples. Doppler spectral phenotyping analysis is used to identify a non-predictive phenotype of TDS that shows a systemic red-shift of frequencies. Doppler spectral shift analysis is used to monitor bacterial infection of living tissue. </p>

This thesis presents two quantitative holographic reconstruction techniques for the imaging of dielectric targets. The first method is a quasi-real-time holographic reconstruction technique, which is capable of imposing physically based constraints on the real and imaginary parts of the permittivity. The other method is a real-time holographic reconstruction technique that is faster than the constrained method but cannot accommodate constraints on the reconstructed permittivity in its current form. The goal of this thesis is to introduce both methods and recommend which is best. Microwave holography has been used by our research group to reconstruct images of a target’s shape and location from microwave scattering parameters. This thesis will demonstrate that holography can be extended to quantify the permittivity distribution in a region of interest. The problems presented in this thesis are generic and are meant to show that near-field quantitative holography is a valid approach for applications such as tissue imaging, baggage inspection, concealed weapon detection, etc. The holographic inversion is carried out in the spectral domain (Fourier space), which allows for the use of Fourier transform properties to expedite the algorithm. This differs from sensitivity-based imaging (another inversion method developed by Tu et al. (2015)) where the inversion is performed in real space and is unable to take advantage of the techniques proposed in this thesis to improve the speed of reconstruction. Mutual coupling is not taken into consideration in the forward model of scattering used here; however, this technique is meant to be viewed as a foundation for a more sophisticated reconstruction algorithm, like the iterative Born method, which can overcome such limitations. Iterative reconstruction methods require an accurate initial guess, which can be provided by the quantitative technique presented in this thesis. Moreover, this technique, implementing fast and efficient linearized inversion, can serve as a module, which is called repetitively by the iterative algorithm. Such a module will take the current estimate of the total field distribution inside the imaged volume as an input and will return an estimate of complex permittivity distribution. / Thesis / Master of Applied Science (MASc)

The scientific community has employed multiple methods to analyze and describe the jet noise emanating from the turbulent exhaust flow from modern military aircraft engines, with the goal that better characterization of the sound radiation will improve noise reduction efforts. This thesis utilizes three different approaches to characterize the noise source region from a static F-22A Raptor. First, the energy flow field along planes near the aircraft and along an arc is measured using a multidimensional vector intensity probe. The resulting vector intensity maps give a clear indication of the directionality of the noise as a function of frequency at different engine conditions. A straightforward ray-tracing method show the utility of vector intensity measurements in source characterization by estimating the region from which the loudest portions of sound are emanating. Second, intensity reconstructions from near-field acoustical holography (NAH) provide an estimate of the three-dimensional radiated energy flow field. The sound field is shown to be dominated by mutually incoherent radiation lobes, which can be partially isolated by a partial decomposition method. Lastly, a wavepacket source model is optimized in light of amplitude-based NAH reconstructions near the jet axis. The wavepacket model successfully fits the NAH-reconstructed partial fields, especially at frequencies above 50 Hz, indicating that the source may be modeled by multiple wave packets at each frequency.

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Real-time holographic recording using an optical heterodyne scanning technique was proposed by Poon in 1985. The first part of this dissertation provides a detailed theoretical treatment of the technique, based on a Gaussian beam analysis. Topics to be addressed include the derivations of the optical transfer function (OTF) and impulse response of the scanning holographic recording system, reconstructed image resolution and magnification, methods of carrier frequency hologram generation and experimental verification of the recording technique based on careful measurements of a hologram corresponding to a simple transmissive slit. Furthermore, computer simulations are presented pertaining to the incoherent nature of the scanning holographic process and it is shown that this new technique can be used to reduce the effects of bias buildup common in conventional incoherent holographic methods. The reconstruction of holograms generated by the heterodyne scanning technique is then considered in the second part of the dissertation. The primary concentration is on real-time reconstruction using an electron beam addressed spatial light modulator (EBSLM). For comparison, experimental coherent reconstruction methods are presented as well. Additional topics to be addressed are the spatial frequency limitations of the EBSLM and the derivation of the overall incoherent point spread function (PSF) for the holographic imaging (recording/reconstruction) system. Based upon the derived overall PSF, the reconstructed real image of a simple slit object is formulated, compared to, and shown to be consistent with experimental observations. / Ph. D.

Optical scanning holography (OSH) [1] has the benefit of recording the entire three-dimensional (3-D) volume of a specimen in the form of a two-dimensional (2-D) hologram. Reconstruction of the original volume can be accomplished by applying digital reconstruction or decoding techniques to the recorded hologram. Accurate reconstruction of the 3-D volume and more specifically, the individual 2-D optical sections without artifacts such as out-of-focus haze from adjacent sections has been the focus of much work including algorithms, optical techniques, and combinations of the two. This dissertation presents several different techniques for enhancing the reconstruction of a recorded specimen and its optical sections including the use of optical coding and phase filtering techniques in the traditional OSH optical system. / Ph. D.

Real-time holography using an active optical heterodyne scanning technique for recording and electron beam addressed spatial light modulator-based reconstruction has recently been studied and demonstrated. Advances in this area are presented in this thesis. For the first time, holograms of two dimensional objects have been recorded and two-dimensional images have been reconstructed using this system. The ability to digitally store holograms recorded by this method has been added to the system. This capability increases the robustness of the overall system and allows for digital processing of the holograms for improved reconstruction. Nonlinear digital processing for fringe contrast enhancement is demonstrated. The use of an intermediate display process has previously been identified as a major drawback in the real-time optical scanning holographic system. A digital frame memory is introduced into the system, eliminating the need for the intermediate display process, and thus improving the system. The two systems are compared. / Master of Science