We propose a novel real-time joint-Transform correlation (JTC) technique for optical pattern recognition. To replace the film recording aspect of performing optical correlation, conventional real-time joint-Transform correlation (JTC) optical systems make use of a spatial light modulator (SLM) located in the Fourier plane to record the interference intensity to achieve real-time processing. However, the use of a SLM in the Fourier plane, is a major drawback in these systems since SLMs are limited in resolution, phase uniformity and contrast ratio. Thus, they are not desirable for robust applications. In this thesis, we developed a hybrid (optical/electronic) processing technique to achieve real-time joint-Transform correlation (JTC). The technique employs acousto-optic heterodyning scanning. The proposed real-time JTC system does not require a SLM in the Fourier plane as in conventional real-time JTC systems. This departure from the conventional scheme is extremely important, as the proposed approach does not depend on SLM issues. We have developed the theory of the technique and substantiated it with optical experimental as well as computer simulation results. / Master of Science

In the temporal study of faint, extended sources at high resolving power, Spatial Heterodyne Spectrometer (SHS) can offer significant advantages about conventional dispersive grating spectrometers. We describe here a four-year continuous progress in Mt. Hamilton, Lick Observatory, toward development of a prototype reflective Spacial Heterodyne Spectrometer, Khayyam, instrument-telescope configuration to combine all of the capabilities necessary to obtain high resolving power visible band spectra of diffuse targets from small aperture on-axis telescopes where significant observing time can be obtained. We will discuss the design considerations going into this new system, installation, testing of the interferometer-telescope combination, the technical challenges and procedures moving forward.

This thesis describes the work undertaken in producing the passive radio-frequency section of a heterodyne receiver for use on the United Kingdom Infra-Red Telescope at signal frequencies in the 200-300 GHz range. This is a Quasi-Optical system, comprised of a Martin-Puplet polarising interferometer employed as a diplexer and the lenses and feed horns by which the diplexer was coupled to the telescope, local oscillator, and mixer. The Gaussian beam-mode approach was employed to develop a theoretical basis for understanding the operation of such a system upon coherent paraxial beams. Quasi-Optical systems were then designed and their performance predicted by the application of this extension of Gaussian optics. Two such systems were constructed and their performance determined by laboratory measurements to be as predicted. One of these systems was then installed on the telescope where it was shown to function as designed. As part of the calibration and test routine on the telescope a number of astronomical measurements were made, including a determination of the apparent temperatures of the planets Jupiter and Saturn by a method different to that employed for results previously published. The Quasi-Optical receiver was successfully calibrated and commissioned as a common-user instrument. As such it will continue to be used in a variety of astronomical research programs undertaken by various groups.

The purpose of this work is to study the interference between the coherent nonresonant four-wave-mixing (FWM) background and the Raman-resonant signal in the coherent anti-Stokes Raman spectroscopy (CARS). The nonresonant background is usually considered as a detriment to CARS. We prove that the background can be exploited in a controllable way, through the heterodyne detection due to the interference, to amplify the signal and optimize the spectral shape of the detected Raman signal, and hence enhance the measurement sensitivity. Our work is based on an optimized CARS technique which combines instantaneous coherent excitation of multiple characteristic molecular vibrations with subsequent probing of these vibrations by an optimally shaped, time-delayed, narrowband laser pulse. This pulse configuration mitigates the nonresonant background while maximizing the resonant signal, and allows rapid and highly specific detection even in the presence of multiple scattering. We investigate the possibility of applying this CARS technique to non-invasive monitoring of blood glucose levels. Under certain conditions we find that the measured signal is linearly proportional to the glucose concentration due to optical interference with the residual background light instead of a quadratic dependence, which allows reliable detection of spectral signatures down to medically-relevant glucose levels. With the goal of making the fullest use of the background, we study the interference between an external local oscillator (nonresonant FWM field) and the CARS signal field by controlling their relative phase and amplitude. Our experiment shows that this control allows direct observation of the real and imaginary components of the third-order nonlinear susceptibility (χ(3)) of the Raman sample. In addition, this method can be used to amplify the signal significantly. Furthermore, we develop an approach by femtosecond laser pulse shaping to precisely control the interference between the Raman-resonant signal and its intrinsic nonresonant background generated within the same sample volume. This technique is similar to the heterodyne detection with the coherent background playing the role of the local oscillator field. By making fine adjustments to the probe field shape, we vary the relative phase between the resonant signal and the nonresonant background, and observe the varying spectral interference pattern. These controlled variations of the measured pattern reveal the phase information within the Raman spectrum, akin to holographic detection revealing the phase structure of a source.

abstract: The Kilopixel Array Pathfinder Project (KAPPa) advances the number of coherent high-frequency terahertz (THz) receivers that could be packed into a single focal plane array on existing submm telescopes. The KAPPa receiver, at 655-695 GHz, is a high frequency heterodyne receiver that can achieve system temperatures of less than 200 K, the specification for ALMA band-9. The KAPPa receiver uses a novel design of a permanent magnet to suppress the noise generated by the DC Josephson effect. This is in stark contrast to the benchmark solution of an electromagnet that is both too expensive and too large for use in kilo-pixel arrays. I present a simple, robust design for a single receiver element that can be tessellated throughout a telescope's focal plane to make a ~1000 pixel array, which is much larger than the current state-of-the-art array, SuperCam, at 64 pixels and ~345 GHz. While the original goal to develop receiver technologies has been accomplished, the path to this accomplishment required a far more holistic approach than originally anticipated. The goal of the present work has expended exponentially from that of KAPPas promised technical achievements. In the present work, KAPPa and its extension, I present solutions ranging from 1) the creation of large scale astronomical maps, 2) metaheuristic algorithms that solve tasks too complex for humans, and 3) detailed technical assembly of microscopic circuit components. Each part is equally integral for the realization of a ~1000 pixel THz arrays. Our automated tuning algorithm, Alice, uses differential evolution techniques and has been extremely successful in its implementation. Alice provides good results for characterizing the extremely complex tuning topology of THz receivers. More importantly, it has accomplished rapid optimization of an entire array without human intervention. In the age of big data astronomy, I have prepared THz heterodyne receiver arrays by making cutting edge community-oriented data analysis tools for the future of large-scale discovery. I present a from-scratch reduction and analysis architecture developed for observations of 100s of square degree on-the-sky maps with SuperCam to address the gulf between observing with single dish antennas versus a truly integrated focal plane array. / Dissertation/Thesis / Doctoral Dissertation Astrophysics 2016

In this report, we give a deeper investigation of the loss-compensated recirculating delayed self-heterodyne interferometer (LC-RDSHI) for ultra-narrow linewidth measurement, including the theoretical analysis, experimental implementation, further modification on the system and more applications. Recently, less than 1kHz linewidth fiber lasers have been commercialized. But even the manufacturers face a challenge on accurately measuring the linewidth of such lasers. There is a need to develop more accurate methods to characterize ultra-narrow laser linewidth and frequency noises. Compared with other currently available linewidth measurement techniques, the loss-compensated recirculating delayed-heterodyne interferometer (LC-RDSHI) technique is the most promising one. It overcomes the bottle-neck of the high resolution requirement on the delayed self-heterodyne interferometer (DSHI) by using a short length of fiber delay line. This method does not need another narrower and more stable laser as the reference which is the necessary component in heterodyne detection. The laser spectral lineshape can be observed directly instead of complicated interpretation in frequency discriminator techniques. The theoretical analysis of a LC-RDSHI gives us a guidance on choosing the optimal parameters of the system and assists us to interpret the recorded spectral lineshape. Laser linewidth as narrow as 700Hz has been proved to be measurable by using the LC-RDSHI method. The non-linear curve fitting of Voigt lineshape to separate Lorentzian and Gaussian components was investigated. Voigt curve fitting results give us a clear view on laser frequency noises and laser linewidth nature. It is also shown that for a ultra-narrow linewidth laser, simply taking 20dB down from the maximum value of the beat spectrum and dividing by $2\sqrt{99}$ will over estimate the laser linewidth and coherent length. Besides laser linewidth measurement in the frequency domain, we also implemented time-domain frequency noise measurement by using a LC-RDSHI. The long fiber delay obtained by a fiber recirculating loop provides a higher resolution of frequency noise measurement. However, spectral width broadening due to fiber nonlinearity, environmental perturbations and laser intrinsic 1/f frequency noises are still potential problems in the LC-RDSHI method. A new method by adding a transmitter switch and a loop switch is proposed to minimize the Kerr effect caused by multiple recirculation. / Ph. D.

Superconductor-Insulator-Superconductor (SIS) mixers are now used regularly in sub- millimetre astronomical receivers. They have already achieved sensitivity approaching the quantum limit at frequencies below the superconducting gap of niobium (~680 GHz). Above that, the mixer performance is compromised by losses, unless materials with higher superconducting gap are employed in conjunction with the niobium tunnel junction. In this thesis, we present the development of 700 GHz niobium SIS mixers, employing a unilateral finline taper on a thin Silicon-On-Insulator (SOI) substrate. These mixers are broadband with full on-chip planar circuit integration, and require only a very simple mixer block. They were designed using rigorous 3-D electromagnetic simulator (HFSS), in conjunction with a quantum mixing software package (SuperMix), and have demonstrated good performance with the best noise temperature measured at 143 K. Our mixer devices were fed by multiple flare angle smooth-walled horns, which are easy to fabricated, yet retain the high performance of corrugated horns. The radiation patterns measured from 600–740 GHz have shown good beam circularity, low sidelobe and cross-polarization levels. In this thesis, we also present SIS mixer designs with balanced and sideband separ- ating capability. These mixers employ back-to-back finline tapers, so that the RF and local oscillator (LO) signals can be injected separately without a beam splitter. We have fabricated and tested the performance of the balanced mixers, and analysed their performance thoroughly. We have also investigated a new method of generating LO signals by beating the tones of two infrared lasers. Using the current 16-pixel 350 GHz SIS receiver, HARP-B, we have observed the ¹²CO J=3→2 emission lines from two nearby galaxies. An important result we found is that the ¹²CO J=3→2 correlates strongly with the 8 μm Polycyclic Aromatic Hydrocarbon emission.

Thesis (D.Sc.)--University of the Witwatersrand, Faculty of Science, 1959.

L'observation du milieu interstellaire est très importante aux fréquences mm / (sub) mm / Thz pour comprendre comment se forment les étoiles et les planètes. De telles observations dépendent des récepteurs hétérodynes. Ces instruments atteignent une résolution spectrale très élevée en convertissant un signal haute fréquence à une fréquence plus basse. Dans un récepteur hétérodyne, le signal collecté est superposé sur un signal artificiel, bien connu, monochromatique, généré par l'oscillateur local (OL), donc ce signal artificiel est plus-ou-moins la fréquence du signal du ciel. Le mélangeur produit le signal de la fréquence du battement. Cette fréquence est équivalente à la différence entre le OL et la fréquence du signal du ciel. Ainsi, le signal du ciel est traduit à une fréquence plus basse, pour qu'il soit facile à amplifier et détecter. Habituellement, les récepteurs hétérodynes ont seulement un pixel spatial avec de nombreux canaux en fréquences. Notre objectif est de développer des réseaux de centaines de pixels. Pour faire cela, certains composants de l'hétérodyne doivent être repensés radicalement, tels que l'antenne de réception et le diviseur de faisceau OL. En effet, l'antenne réceptrice est généralement constituée d'une antenne à double fentes sur une lentille, ou d'une antenne cornet. Par contre, ces antennes ne sont pas les meilleurs choix pour des réseaux de nombreux pixels car elles doivent être usinées et montées individuellement. Au lieu de cela, il est commode de développer des structures planaires qui peuvent être facilement produites toutes ensembles. En particulier, nous avons conçu et simulé des réseaux d'antennes patch, de réseaux de transmission, et de plaques de zone. Le réseau d'antennes patch consiste d'un réseau de patchs métalliques reliés par une ligne microruban et séparés du plan de masse par un substrat diélectrique. Cette configuration profite du facteur du réseau pour réduire la largeur de faisceau du signal collecté. Cependant, nos simulations nous montrent que la bande RF des réseaux d'antennes patch est étroite. Pour cette raison, nous avons analysé la possibilité d'utiliser une autre solution : le réseau de transmission. C'est un réseau de plusieurs cellules qui déphase une onde afin de transformer son front de phase de forme planaire en forme sphérique. Le but de la matrice de transmission est de focaliser le faisceau collecté vers une antenne et mélangeur à double fentes. La thés démontre qu'un effet de focalisation satisfaisant est atteint sur une ligne. Nous avons fabriqué un tel réseau de transmission et l'avons testé en laboratoire. En raison des petites dimensions de quelques millimètres, ces tests sont difficiles à réaliser. Au sein de l'erreur de mesure, la conception et les simulations sont cohérentes. Une troisième option (d'une lentille planaire) a été étudiée dans la thèse : la plaque de zone. C'est un type particulier de réseau de transmission qui ne présente que deux déphasages de 0 ° et 180 °. Le plaque de zone focalise bien, mais est peu efficace. La dernière partie de la thèse introduit un type de diviseur de faisceau particulier qui permet une division du faisceau du signal OL vers un réseau de quatre mélangeurs très serrés. Diviser le faisceau avec des angles suffisamment petits est très difficile avec les réseaux de Fourier et Dammann classiques. Pour cette raison la méthode que nous avons proposée pour concevoir un tel diviseur est très novatrice. En effet, il permet la formation de motifs de faisceaux de forme arbitraire, qui ne sont pas limités par les ordres de diffraction. Les simulations montrent des efficacités allant jusqu'à 80% qui sont très bonnes en comparaison avec les réseaux classiques. En résumé, dans cette thèse, j'ai essayé plusieurs moyens radicalement différents pour simplifier les récepteurs hétérodynes et ouvrir la voie aux grandes matrices hétérodynes avec des centaines de pixels. / The observation of the interstellar medium is very important at mm/(sub)mm/THz frequencies to understand how stars and planets form. Generally such observations rely on heterodyne receivers. These are instruments that achieve very high spectral resolution by down converting a high frequency signal towards a lower frequency one. In a heterodyne receiver the incoming signal is superimposed onto an artificial, well-known, monochromatic signal generated by the local oscillator (LO), chosen to be close to the frequency of the sky signal. The mixer produces the beat frequency signal. It has a frequency equivalent to the difference between the LO and sky signal frequency. Thus the sky signal is translated to a lower frequency, and it is easier to amplify and detect. Usually heterodyne receivers have only one spatial pixel with many frequency channels. Some prototypes have been realized recently with few pixels. Our objective is to develop arrays of hundreds of pixels. In order to do that, some components which compose the heterodyne receiver must be radically rethought, such as the receiving antenna and the LO beam divider.Indeed the receiving antenna generally consists of a double slot antenna on a lens, or a horn antenna. Such antennas are not the best choice for arrays of many pixels since they have to be machined and mounted individually. Instead it is convenient to develop planar structures which can be easily produced in bulk in a single process. In particular we designed and simulated arrays of patch antennas, transmit-arrays and zone plates. The array of patch antennas consists of an array of metallic patches connected via a microstrip line and separated from the ground plane by a dielectric substrate. This configuration takes advantage of the array factor to reduce the beamwidth of the incoming signal in place of the lens. However our simulations showed the array of patch antennas to be quite narrowband for a general purpose application, and quite difficult to realize. For this reason we also analyzed the possibility to use another solution such as the transmit-array. It is an array of several cells which provide a certain phase shift to an incoming wave in order to transform its phase front from planar to spherical. The purpose of the transmit-array is to focus the incoming beam towards a double slot antenna and a mixer placed below it. The simulations showed that a good focusing effect can be reached on a line. We fabricated such a transmit-array and tested it in the laboratory. Because of the small dimensions of a few millimeters these tests are difficult to carry out. Within the measurement error design and simulations are consistent. A third option of a planar lens was studied in the thesis: the zone plate. This is a particular kind of transmit-array which presents only two phase shift of 0° and 180°. The zone plates focus well, but are unfortunately not very efficient.The final part of the thesis introduces a particular kind of beam divider which allows beam splitting of the LO signal towards an array of four very closely packed mixers. To split the beam with such small relative angles is very difficult with the classical Fourier and Dammann grating, for this reason the method we proposed to design such a beam divider is very innovative. Indeed it allows the forming of arbitrary shaped beam patterns, which are not limited by the diffraction orders. Simulations show efficiencies up to 80% which are very good in comparison with classical gratings.In summary in this thesis I have tried several radically different approaches to simplify heterodyne receivers and made a first step towards for large heterodyne arrays with hundreds of pixels.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by David Michael Papurt. / Ph.D.