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Dissertations / Theses on the topic 'Infrared waves'
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Naraniya, Om Prakash. "Studies on efficient mid-infrared generation using quasi-phase-matched second order nonlinear interactions in ferroelectric substrates." Thesis, IIT Delhi, 2016. http://localhost:8080/iit/handle/2074/7065.
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STEIJN, KIRK WILLIAM. "COUPLING AND PROPAGATION OF SURFACE PLASMONS IN THE FAR-INFRARED (NEAR-MILLIMETER WAVES, SUB-MILLIMETER WAVES)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183973.
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This work describes a study of the propagation properties of a modified surface plasmon mode, and of the coupling properties of that mode using a grating coupler. The surface plasmon, a polariton involving coupling of electromagnetic waves to the plasma oscillations of a metal, is modified by the application of a dielectric overlayer to the interface between the metal and air. In the far infrared region of the electromagnetic spectrum, the overlayer causes dramatic changes in several properties of the mode, which can be verified by measuring the propagation length of the mode. Measurements at a wavelength of 118.8 μm of the propagation length as a function of the thickness of a polycrystalline silicon overlayer on silver showed that the mode has the expected properties. They also indicated that the Drude model of the dielectric function of the silver is valid at 118.8 μm, even when using established Drude parameters, which are based on measurements in the visible and near infrared region of the electromagnetic spectrum. The coupling study measured the fundamental coupling parameters, also at a wavelength of 118.8 μm, for coupling via a grating between free-space waves and the surface plasmon, and measured the effect of the overlayer on these parameters. Efficient coupling was achieved, but a theoretical treatment of the coupling system proved to be beyond the scope of first-order grating-coupler theory. This was true despite the fact that the grating amplitude was a small fraction of the wavelength, a common criterion for the application of such a theory. Several possible reasons for the breakdown of the theory were considered, but definite answers require additional experiments. The most prominent possibilities are the shape factor, and the depth of the grating compared to the penetration depth of the fields into the metal. Though not all the data is completely explained, the studies herein demonstrate that the overlayer eliminates many of the deficiencies which limit the generation and control of far-infrared surface plasmons.
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Ward, Barry. "Generation of acoustic waves by focused infrared neodymium-laser radiation." Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/10626.
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When the radiat Ion from a sufficient Iy powerful pulsed laser Is focused into transparent gaseous, liquid or solid media, dielectric breakdown may occur around the beam waist giving rise to a shortI ived high-temperature plasma which quickly heats the surrounding material. As a consequence of various energy-coupling mechanisms, this phenomenon causes the emission of one or more high-frequency ultrasonic acoustic waves whose speeds of propagation are dependent upon the physical propert les of the host medium. In the high-speed photographic studies described In this doctoral thesis, the 1.06-l'm near-Infrared radlat Ion from an 8-ns, lO-mJ Q-swl tched Nd:YAG laser Is focused In or onto a variety of fluid and solid materials. The rapid variations In density around the resulting plasma events are visualised using a Mach-Zehnder Interferometer with a sub-nanosecond dye-laser light source and a vldeo-Imaglng system. Calculat Ions of the corresponding transient pressure distributions are then enacted from the digitally-recorded Interferograms using a semi-automat Ic procedure under the control of a personal computer. Measurements of position. displacement and velocity are also carried out using the same opt ical apparatus In schlleren and focused shadowgraph highspeed photographic arrangements. The experimental work outlined In the following chapters is divided Into three broad fields of Interest. In the first of these, a study of the laser-generation of spherical shock waves· in atmospheric air is carried out. In the second, the neOdymium-laser beam Is focused onto different solid-fluid Interfaces resulting In the formation of bulk longitudinal and shear waves and surface acoustic waves. The Interactions of these waves with various obstacles and defects are Investigated with reference to their application to non-destructive test Ing. In the third and most important field, a detailed study of the dynamics of laser-Induced cavitation bubbles In water Is carried out. With regard to the associated phenomenon of cavitation erosion, particular attention Is paid to the formation of spherical acoustic waves by radlally-oscillatlng vapour cavities at various distances from transparent rigid boundaries.
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Zappa, Christopher Joseph. "Microscale wave breaking and its effect on air-water gas transfer using infrared imagery /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10184.
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Rønning, Snorre Stavik. "Optimizing an Infrared Camera for Observing Atmospheric Gravity Waves from a CubeSat Platform." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20915.
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The NTNU Test Satellite (NUTS) is a double CubeSat deigned by master students at NTNU. The goal of the project is to image atmospheric gravity waves in the OH airglow layer. This thesis explores the theory behind gravity waves and discuss the design of an infrared camera as a payload onboard. Different requirement based on scientific and mechanical limitations are presented. Based on this a suitable infrared camera is presented.
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Krisch, Isabell [Verfasser]. "Tomographic observations of gravity waves with the infrared limb imager GLORIA / Isabell Krisch." Wuppertal : Universitätsbibliothek Wuppertal, 2020. http://d-nb.info/1216653283/34.
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Mickan, Samuel Peter. "T-ray biosensing /." Title page, table of contents and abstract only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phm6253.pdf.
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Ferguson, Bradley Stuart. "Three dimensional T-Ray inspection systems /." Title page, Table of contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phf3521.pdf.
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Khalaf, Reem. "Image reconstruction for optical tomography using photon density waves." Thesis, University of Hertfordshire, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302304.
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Kucheruk, V. Yu, I. A. Dudatiev, В. Ю. Кучерук, and І. А. Дудатьєв. "Physical nature metrological select of range of infrared waves to optical absorbtion methods of control flue gas boilers." Thesis, ВНТУ, 2013. http://ir.lib.vntu.edu.ua/handle/123456789/8105.
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Martínez-Sansigre, Alejo. "Distant obscured quasars." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:a764a410-4464-4b92-831d-34e8a383d78f.
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This thesis presents a study of high-redshift obscured (type-2) quasars, selected at mid-infrared and radio wavelengths. This population had remained elusive, even to hard X-ray surveys, and in Chapter 2 I compare the selection of type-2 quasars in X-ray and mid-infrared surveys, as well as explaining the criteria I will use to search for these objects at z ~ 2, around the peak in the unobscured (type-1) quasar activity. Chapter 3, presents a sample of radio-intermediate type-2 quasars selected from the criteria de- scribed in Chapter 2. Optical spectroscopy shows indeed that at least half of the objects have the characteristic narrow emission lines, and lie around the expected redshift of z = 2. The other half of the objects are consistent with also being type-2 quasars at similar redshifts, although no emission lines are visible. In Chapter 4,1 discuss the possibility of two types of obscured quasars, some obscured by a dusty torus and some by a dusty host galaxy, to explain the lack of emission lines in half of the sample. I model the number of type-1 quasars expected to follow similar selection criteria and at the same redshifts as our type-2 quasars, and find that the obscured quasars outnumber the unobscured by a ~2-3:1 ratio. I conclude that most supermassive black hole growth is obscured by dust. When comparing this to predictions from unified schemes, I find that this result is only consistent with the schemes provided host-obscuration is indeed happening. The lower ratio of type-2 to type-1 quasars inferred from X-ray surveys (~1:1) suggests that some of the type-2 quasars in this sample might be Compton thick. Radio data taken at three frequencies, are presented in Chapter 5, to study the spectral properties and intrinsic luminosities of our sample. I show that some type-2 quasars have flat radio spectra, which is inconsistent with obscuration by the torus, but consistent with host-obscuration. Some gigahertz-peaked spectra, characteristic of young radio jets, are present, but the majority of the sources have very steep spectra. These steep spectral indices can be explained by active developed jets in which continuous injection of electrons is accompanied by inverse-Compton losses against the cosmic microwave background. In Chapter 6, I select a similar sample of type-2 quasars in a different field, where X-ray data are available. The selection criteria are kept identical, except for the radio flux density cut, which is lowered. This is expected to introduce significant numbers of starburst contaminants. To filter these out, and due to a lack of spectroscopy, I use a bayesian method to fit the spectral energy distributions, obtain photometric redshifts, and select between a quasar and a starburst model. I measure the X-ray properties for the resultant sample of type-2 quasars. The entire sample is found to be Compton-thick, and repeating the modelling of Chapter 4, I find that the population of Compton-thick quasars is at least comparable to the population of unobscured quasars, and probably larger.
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Cowperthwaite, P. S., E. Berger, V. A. Villar, B. D. Metzger, M. Nicholl, R. Chornock, P. K. Blanchard, et al. "The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626064.
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We present UV, optical, and near-infrared (NIR) photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at 0.47-18.5 days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/ FLAMINGOS-2 (GS/F2), and the Hubble Space Telescope (HST). The spectral energy distribution (SED) inferred from this photometry at 0.6 days is well described by a blackbody model with T approximate to 8300 K, a radius of R approximate to 4.5 x 10(14) cm (corresponding to an expansion velocity of v approximate to 0.3c), and a bolometric luminosity of L-bol approximate to 5 x 10(41) erg s(-1). At 1.5 days we find a multi-component SED across the optical and NIR, and subsequently we observe rapid fading in the UV and blue optical bands and significant reddening of the optical/ NIR colors. Modeling the entire data set, we find that models with heating from radioactive decay of Ni-56, or those with only a single component of opacity from r-process elements, fail to capture the rapid optical decline and red optical/NIR colors. Instead, models with two components consistent with lanthanide-poor and lanthanide-rich ejecta provide a good fit to the data; the resulting "blue" component has M-ej(blue) approximate to 0.01 M-circle dot and v(ej)(blue) approximate to 0.3c, and the "red" component has M-cj(red) approximate to 0.04 M-circle dot and v(cj)(red) approximate to 0.1 c. These ejecta masses are broadly consistent with the estimated r-process production rate required to explain the Milky Way r-process abundances, providing the first evidence that binary neutron star (BNS) mergers can be a dominant site of r-process enrichment.
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Trujillo, Victor Esteban. "Global Shipping Container Monitoring Using Machine Learning with Multi-Sensor Hubs and Catadioptric Imaging." W&M ScholarWorks, 2019. https://scholarworks.wm.edu/etd/1582642585.
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We describe a framework for global shipping container monitoring using machine learning with multi-sensor hubs and infrared catadioptric imaging. A wireless mesh radio satellite tag architecture provides connectivity anywhere in the world which is a significant improvement to legacy methods. We discuss the design and testing of a low-cost long-wave infrared catadioptric imaging device and multi-sensor hub combination as an intelligent edge computing system that, when equipped with physics-based machine learning algorithms, can interpret the scene inside a shipping container to make efficient use of expensive communications bandwidth. The histogram of oriented gradients and T-channel (HOG+) feature as introduced for human detection on low-resolution infrared catadioptric images is shown to be effective for various mirror shapes designed to give wide volume coverage with controlled distortion. Initial results for through-metal communication with ultrasonic guided waves show promise using the Dynamic Wavelet Fingerprint Technique (DWFT) to identify Lamb waves in a complicated ultrasonic signal.
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Brilla, Pavol. "Realizace zařízení pro měření rozptylu elektromagnetického záření ve struktuře solárních článků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229105.
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The master thesis discusses the principles, design and realization of the original device for measuring of the electromagnetic radiation scattering in the structure of solar cells. It follows the results of a previous project "Analýza optických vlastností solárných článku" (ev.n.FT-TA3/142) and as well as knowledge gained from Ing. Vladimir Grundling’s master thesis, which has been done under this project. The subject of this thesis was to make a device for measuring of the electromagnetic radiation scattering in the visible spectrum. The aim of this work is an innovation of the previous device, so that the electromagnetic radiation scattering in the near infrared spectrum can be studied. This makes the possibility to qualify the influence of the rear surface of an active part of solar cell on electromagnetic radiation scattering, i.e., on the conversion efficiency of solar energy into electric. For this reasons it was necessary to modify the device, so that we can change the radiation source and detector because of the transparency of silicon wafers for the near infrared area. The work is supported by the project „Barevné solární články s vysokou účinností pro architektonické aplikace“ (FRTI1/168) in cooperation with Solartec s.r.o.
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Shu, Bo [Verfasser], and Christof [Akademischer Betreuer] Schulz. "Mid-infrared absorption sensor for CO concentration and temperature measurements for pyrolysis and oxidation behind reflected shock waves / Bo Shu ; Betreuer: Christof Schulz." Duisburg, 2018. http://d-nb.info/1155722744/34.
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Leiton-Thompson, Roger. "Resolving the cosmic infrared background with the Herschel space observatory." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112146.
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Au cours des dernières décennies, l’astronomie infrarouge a changé notre point de vue au sujet de l’évolution des galaxies, en particulier à de grandes distances. Nous avons accès à une grande variété d’informations physiques grâce au domaine spectral infrarouge. Toutefois, les limites de diffraction des instruments infrarouges et l’existence d’un grand nombre de sources font de l’identification individuelle des galaxies une tâché difficile. La première partie de cette thèse est consacrée à Résoudre le fond extragalactique infrarouge avec l’observatoire spatial Herschel, à, l’aide de simulations réalistes, correspondant aux images les plus profondes jusqu’ici obtenues en infrarouge lointain. Nous avons étudié l’origine du bruit de confusion dans les images GOODS-Herschel et résolu une partie de fond cosmique infrarouge en galaxies individuelles. De nouvelles techniques ont été développées pour prédire les flux en infrarouge lointain à partir de la connaissance préalable des positions, décalages spectraux et densités de flux des sources dans l’infrarouge moyen. Les images simulées ont été construites en utilisant les flux prédits afin d’évaluer le rôle du bruit local de confusion et d’identifier des sources individuelles. La deuxième partie de la thèse concerne l’étude de la Destruction de grains de poussières par des jets vus en radio. Nous avons étudié les effets des noyaux actifs de galaxies dans le milieu interstellaire, en particulier le mécanisme qui donne lieu à la région des raies étroites dans les galaxies de type Seyfert. Des spectres en infrarouge proche à fente longue a ont été enregistrés sur un ensemble de galaxies Seyfert de type 2 afin de mesurer les raies d’émission de ([Fe II], [P II] et Paβ) qui révèlent la destruction de poussières par les ondes de choc produites par les jets radio. Nous avons constaté que le mécanisme dominant l’ionisation près du noyau des galaxies Seyfert est le champ de rayonnement produit par l’activité du trou noir. Dans la partie extérieure de la région des raies étroites, des ondes de choc induites par des jets de radio contribuent également au budget énergétique du milieu interstellaire et à la destruction des grains de poussière. Cette thèse s’est déroulée en co-encadrement au Service d’Astrophysique du CEA-Saclay et au Département d’Astronomie de l’Université de Concepción, au ChiliDuring the last decades, infrared astronomy has changed our view about the evolution of galaxies, especially at large distances. We have access to large variety of physical information in the infrared bands. However, diffraction limits of the infrared instruments and the existence of a large number of sources makes individualization of galaxies a difficult task. The first part of this thesis is entitled Resolving the Cosmic Infrared Background with the Herschel Space Observatory where, by the use of far-infrared realistic simulations of the deepest infrared images of the Universe, we have studied the origin of the confusion noise in the GOODS-Herschel images and resolved a substantive part of the Cosmic Infrared Background into individual galaxies. New techniques were developed to predict the fluxes in the far-infrared from prior knowledge in the mid-infrared. Mock images were built using those predicted fluxes to evaluate the role of local confusion noise and identify individual sources. The second part of the thesis concerns the study of the Destruction of dust grains by radio jets. We study the effects of active galactic nuclei in the insterstellar medium, in particular in the mechanism that gives rise to the narrow-line region in Seyfert galaxies. Long-slit near-Infrared spectra of a set of type-2 Seyfert galaxies were taken to measure diagnostic emission lines ([Fe II], [P II] and Paβ) that reveal the destruction of dust grains due to the shock waves produced by the radio jets. We found that the dominant mechanism of ionization close to the nuclei of the Seyfert galaxies is the radiation field produced by the back hole activity. In the outer part of the narrow-line region, shock waves induced by the radio jets also contribute to the energy budget of the interstellar medium and sputter the dust grains. This was a co-advising thesis performed in the Service d’Astrophysique CEA-Saclay and the Astronomy Department of the University of Concepción, Chile
Durante las últimas décadas, la astronomía infrarroja ha cambiado nuestra visión sobre la evolución de galaxias, en especial revelando que a grandes distancias (z >1) las galaxias individuales son típicamente Galaxias Infrarrojas Ultraluminosas (cuyas siglas en inglés son ULIRGs por Ultraluminous Infrared Galaxies, 1012 < Lbol < 1013 L⊙). Actualmente tenemos acceso a una gran variedad de información física basada en la emisión en bandas espectrales infrarrojas (IR), radiación que en el caso de las galaxias es producida en su mayoría por granos de polvo. Sin embargo, el límite de difracción de los instrumentos infrarrojos junto con el gran número de fuentes de emisión hace de la individualización de galaxias una tarea difícil. La primera parte de esta tesis se titula Resolviendo el Fondo Cósmico Infrarrojo con el Observatorio Espacial Herschel donde, con el uso de simulaciones realistas de las imágenes más profundas del Universo, hemos estudiado el origen del ruido de confusión en las imágenes GOODS-Herschel y resuelto en galaxias individuales una parte sustantiva del Fondo Cósmico Infrarrojo. Nuevas técnicas fueron desarrolladas para predecir los flujos en el infrarrojo lejano a partir del conocimiento a priori en el infrarrojo medio. Las imágenes simuladas fueron construidas usando esos flujos predichos y con ellos evaluar el rol del ruido de confusión local así como identificar fuentes individuales. La segunda parte de la tesis trata del estudio sobre la Destrucción de granos de polvo por chorros en ondas de radio. Este proyecto que se concentró en la observación de galaxias Seyfert y ULIRGS y apunta a entender mejor el ciclo de vida del polvo al estudiar la destrucción de granos en galaxias con nucleos activos y los efectos de la actividad de estas últimas en el medio interestelar, en particular en el mecanismo que da origen a la región de líneas de emisión angostas en las galaxias Seyfert. Se obtuvo espectros infrarrojos de rendija larga de galaxias Seyfert del tipo 2 para medir líneas de emisión ([Fe II], [P II] y Paβ) las cuales revelan la destrucción de granos de polvo debido a las perturbaciones de las ondas de choque producidas por chorros detectados en ondas de radio. Hemos encontrado que el mecanismo dominante de la ionización cerca de los núcleos de las galaxias Seyfers es el campo de radiación producido por la actividad del agujero negro central. En la parte externa de la región de líneas de angostas, las ondas de choque inducidas por los chorros en radio también contribuyen al balance energético del medio interestelar y desintegran los granos de polvo. Esta fue una tesis de co-tutela llevada a cabo en el Departamento de Astronomía de la Universidad de Concepción y en el Service d’Astrophysique del Commissariat á l’Énergie Atomique (CEA), Francia
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Erdozain, Jack Jr. "Long wave infrared structured light." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121664.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 69-72).
3D sensing technologies have been exploited for many applications in autonomous vehicles, manufacturing, and consumer products, however, existing techniques may suer in challenging conditions, where scattering due to fog, dust, or smoke is present. While light in the visible and near IR spectrum are heavily affected by by common scattering mediums, long-wave infrared (also known as thermal IR) experiences less scattering, especially when scattering particles are small. This thesis proposes and demonstrates a structured light scanning approach which operates in the long-wave IR Spectrum. We believe that structured light technique with long-wave IR leads to more robust 3D sensing in some challenging environments. In this thesis the conceptual framework behind the technology is presented, the technology is demonstrated, and testing of long-wave infrared projection is compared to the visible spectrum.
by Jack Erdozain Jr.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Sevison, Gary Alan. "Silicon Compatible Short-Wave Infrared Photonic Devices." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1523553057993197.
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Franke, Daniel. "Fluorescent materials for short-wave infrared imaging." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/121616.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2018
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 223-247).
Our understanding of the fundamental processes that drive biology and medicine is, in large part, based on our ability to visualize biological structures and monitor their transformations over time. Fluorescence imaging is one of the most transformative technologies of modern biomedical imaging as it provides a low cost, high sensitivity method for real-time molecular imaging in vivo. As the scattering and absorption of light through biological tissue impose significant restrictions on imaging penetration depth, acquisition speed, and spatial resolution, the development of novel optical imaging technologies has increasingly shifted toward the use of light of longer wavelengths. Fluorescence imaging in the shortwave infrared (SWIR, 1000 - 2000 nm) spectral region mitigates the negative effects of light attenuation and benefits from a general lack of tissue autofluorescence.
As a result, SWIR imaging promises higher contrast, sensitivity, and penetration depths compared to conventional visible and near-infrared (NIR) fluorescence imaging. However, the lack of versatile and functional SWIR emitters has prevented the general adoption of SWIR imaging both in academic and clinical settings. Here, we will present progress toward the synthesis of a new generation of SWIR-emissive materials and discuss their use in enabling biomedical imaging applications. In the first part of this thesis, we will examine the synthesis of SWIR-emissive indium arsenide (InAs) quantum dots (QDs). To address existing challenges in the synthesis of these semiconductor nanocrystals, we will investigate the processes that govern nanoparticle formation and growth.
Combining experimental and theoretical methods, we demonstrate that the synthesis of large nanocrystals is hindered by slow growth rates for large particles, as well as the formation and persistence of small cluster intermediates throughout nanocrystal growth. Based on these insights, we design a novel, rational synthesis for large InAs QDs with high brightness across the SWIR spectral region. Second, we will discuss the use of InAs-based QDs in functional SWIR imaging applications in pre-clinical settings. We will present three QD surface functionalizations that enable the non-invasive real-time imaging of hemorrhagic stroke, the quantification of metabolic activity in genetically-engineered animals, and the measurement of hemodynamics in the brain vasculature of mice. In addition, we will present preliminary results for the synthesis of SWIR-emissive QD probes for the molecular targeting of biological entities and for advanced particle tracking applications.
Using a QD-based broadband SWIR emitter, we will further investigate the eæect of SWIR imaging wavelength on image contrast and tissue penetration depth. While it was previously assumed that reduced scattering of light at longer wavelengths is the primary cause for increased image contrast, our results indicate that for imaging scenarios with strong fluorescent background signals, image contrast and penetration depth correlate closely with the absorptive properties of biological tissue. As a result, deliberate selection of imaging wavelengths at which biological tissue is highly absorptive can help to overcome contrast-limited imaging scenarios. In the last part of this thesis, we will take a closer look at SWIR emitters with the potential for translation into clinical settings.
We will demonstrate that the FDA-approved NIR dye indocyanine green (ICG) exhibits an unexpectedly high SWIR brightness that arises from a large absorption cross-section and a vibronic shoulder in its fluorescence spectrum that extends well into the SWIR spectral region. We expand on this finding by showing that ICG outperforms commercial SWIR dyes during in vivo imaging, and additionally by demonstrating a variety of high-contrast and high-speed imaging applications in small animals. These results suggest that ICG enables the direct translation of SWIR imaging into the clinic. In summary, this thesis will paint a comprehensive picture of the current state of SWIR-emissive materials, present the synthesis of novel versatile SWIR probes, and show their application in unprecedented functional SWIR imaging applications.
by Daniel Franke.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry
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KOMATSU, LUIZ G. H. "Estudo comparativo de nanocompósitos de polipropileno modificado sob condições de envelhecimento ambiental e acelerado." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26380.
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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T12:34:18Z
No. of bitstreams: 0Made available in DSpace on 2016-06-22T12:34:18Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Padhye, Anuja Arun. "Novel continuous-wave infrared parametric sources and noise analysis of infrared upconversion detectors." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669321.
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The ability to manipulate frequency of light, through parametric frequency conversion sources based on X(2) nonlinear materials, offers an effective route to spectral regions unapproachable by conventional lasers. Most importantly, three-wave mixing processes provide tunable coherent radiation over a broad spectral range. Among the most important tunable devices, narrow linewidth continuous-wave (cw) infrared (IR) optical parametric oscillators (OPOs) are indispensable excitation sources for many applications in molecular spectroscopy and precision metrology. In order to exploit such applications, the development of cw OPOs deploying different wavelength tuning schemes and novel nonlinear materials is highly dezirable, as presented in this thesis. We demonstrated a rapidly tunable cw OPO based on fan-out grating design periodically-poled KTiOPO4 (PPKTP) crystal at room temperature. This approach allows continuous wavelength tuning by avoiding increased thermal fluctuations at higher operating crystal temperatures. The 532 nm-pumped, output-coupled singly-resonant oscillator (OC-SRO) provides widely tunable near-IR radiation across 741-922 nm and 1258-1884 nm, with total output power of 1.65 W. The use of output coupling for the resonating wave reduces thermal loading and enables 30% enhancement in the OPO extraction efficiency over the pure SRO configuration. Towards the goal of developing a next-generation cw source >4 µm using a new found quasi-phase-matched semiconductor material, orientation-patterned gallium phosphide (OP-GaP), we demonstrated the first realization of a tunable cw mid-IR source based on OP-GaP by exploiting single-pass difference-frequency-generation (DFG) between a Tm-fiber laser at 2010 nm and a home-built OPO based on MgO-doped periodically-poled LiNbO3 (MgO:PPLN) crystal. The DFG source generates up to 43 mW of output power, with >30 mW across 96% of the tuning range 4608-4694 nm, in high beam quality. As the tunable mid-IR sources are making great strides, the availabilityof fast and sensitive mid-IR detectors become equally important. However, the conventional mid-IR detectors demand cryogenic systems for low-noise operation which sets a major drawback as these devices are often bulky and expensive. In this context, the nonlinear frequency upconversion technique has emerged as a promising alternative to the direct detection of mid-IR radiation at room temperature. An upconversion detector (UCD) can be further optimized by identifying and suppressing its noise sources. In order to do so, we experimentally and theoretically investigated noise properties of 1064 nm-pumped single-pass UCD designed for signal detection in telecom and mid-IR range using MgO:PPLN crystals. We studied the dependence of newly discovered SHG (532 nm)-induced spontaneous parametric downconversion (SHG-SPDC) noise intensity on the pump power and crystal temperature, and compared it with the well-known UCD noise source upconverted spontaneous parametric downconversion (USPDC). The measurements deduce that SHG-SPDC must be given a careful consideration since it can act as a dominant noise source under certain operating conditions. However, SHG-SPDC can be avoided by choosing a proper combination of MgO:PPLN grating period,operating temperature, and bandpass filter.La capacidad de manipular la frecuencia de la luz, a través de sintonizables fuentes de conversión de frecuencia paramétrica basadas en materiales no lineales del tipo ¿(2), ofrece un acceso eficaz a las regiones espectrales inaccesible por los láseres convencionales. Entre los dispositivos sintonizables más importantes, los osciladores ópticos paramétricos (OPOs) de onda continua (cw) en el infrarrojo (IR) con ancho de banda estrecho, son fuentes esenciales para muchas aplicaciones en espectroscopia molecular y metrología de precisión. Con el fin de explotar tales aplicaciones, es muy deseable el desarrollo de OPOs de cw mediante diferentes esquemas de sintonización de longitud de onda y nuevos materiales no lineales, como se presentan en esta tesis. Mostramos aquí un OPO de cw rápidamente sintonizable basado en un cristal periodically-poled KTiOPO4 con diseño de red fan-out a temperatura ambiente. Este enfoque permite una sintonización continua de la longitud de onda evitando el aumento de las fluctuaciones térmicas a temperaturas de funcionamiento más altas de los cristales. El OPO resonante con acoplador de salida bombeado a longitud de onda de 532 nm, proporciona radiación sintonizable en el infrarrojo cercano (near-IR) a través de 741-922 nm y 1258-1884nm, con una potencia de salida máxima de 1.65 W. El uso del acoplador de salida para la onda resonante reduce la carga térmica y permite una mejora del 30% en la eficiencia de extracción del OPO sobre la configuración SRO pura. Con el objetivo de desarrollar la nueva generación de fuentes de onda continua con longitud de onda >4 µm utilizando la técnica de quasi-phase-matching con materiales semiconductores, presentamos la primera demostración de una fuente de onda continua sintonizable en el infrarrojo medio (mid-IR) utilizando el patrón de orientación de fosfuro de galio (OP-GaP) y generación de frecuencia diferencia (DFG) entre láser de fibra Tm a longitud de onda de 2010 nm y otro OPO hecho en el laboratorio basado en un cristal MgO-doped periodically-poled LiNbO3 (MgO:PPLN). La fuente DFG genera hasta 43 mW de potencia de salida, con >30 mW a través de un 96% del rango de sintonización 4608-4694 nm, con una alta calidad de haz. A medida que las fuentes de emisión en el mid-IR sintonizables mejoren sus prestaciones, la disponibilidad de detectores de mid-IR rápidos y sensibles se vuelve igualmente importante. Sin embargo, los detectores de mid-IR convencionales requieren sistemas criogénicos para operar con poco ruido, lo que presenta un gran inconveniente ya que estos dispositivos suelen ser voluminosos y caros. En este contexto, la técnica no lineal de conversión ascendente de frecuencia ha surgido como una alternativa prometedora a la detección directa de la radiación de mid-IR a temperatura ambiente. Un detector de conversión ascendente (UCD) se puede optimizar aún más dentificando y suprimiendo sus fuentes de ruido. Para hacerlo, investigamos teórica y experimentalmente las propiedades de ruido de un UCD de un solo paso bombeado a 1064 nm diseñado para la detección de señales en telecomunicaciones y rango mid-IR, utilizando cristales MgO:PPLN. Descubrimos una nueva fuente de ruido llamada ruido espontáneo paramétrico de conversión descendente inducido por generación de segundo harmónico SHG (SHG-SPDC). Estudiamos, también, la dependencia de la intensidad de este ruido (SHG-SPDC) con la potencia de bombeo y la temperatura del cristal. Finalmente, también comparamos su intensidad con el conocido ruido generado por el detector UCD, llamado ruido de conversión ascendente por conversión paramétrica descendente espontánea (USPDC). Los resultados obtenidos nos dicen que se debe considerar cuidadosamente el SHG-SPDC, ya que puede actuar como una fuente de ruido dominante en ciertas condiciones de operación. Sin embargo, el SHG-SPDC se puede evitar al elegir una combinación adecuada de MgO:PPLN, el período de red la temperatura de operación y el filtro de tipo pasa banda.
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Haran, Terence. "Short-Wave Infrared Diffuse Reflectance of Textile Materials." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/phy_astr_theses/5.
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This thesis analyzes the reflectance behavior of textiles in the short-wave infrared (SWIR) band (1 – 2 microns) in order to identify/design potential diagnostic tools that allow the remote detection of human presence in a scene. Analyzing the spectral response of fabrics in the SWIR band has gained significant interest in the remote sensing community since it provides a potential path to discriminate camouflaged clothing from backgrounds that appear similar to the object of interest in the visible band. Existing research, originating primarily from the textiles community, has thoroughly documented the behavior of clothing fabrics in the visible band. Other work has shown that the differences in spectral response in the SWIR band allows for discrimination of materials that otherwise have the same visible spectral response. This work expands on those efforts in order to quantify the reflectance behavior and to better understand the physical basis for that behavior.
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Harizi, Walid. "Caractérisation de l'endommagement des composites à matrice polymère par une approche multi-technique non destructive." Thesis, Valenciennes, 2012. http://www.theses.fr/2012VALE0033.
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Cette étude novatrice consiste à mettre en oeuvre dans un même protocole expérimental, trois techniques de caractérisation non destructive en simultané : l’émission acoustique, la thermographie infrarouge et les ultrasons pour la caractérisation de l’endommagement des matériaux Composites à fibres continues et à Matrice Polymère (CMP) à plis croisés [0/90]S. Chaque technique a permis demontrer sa potentialité à révéler l’endommagement dépendant de ses spécificités intrinsèques. L'émission acoustique a été utilisée sous sa forme classique et couplée avec une classification de données obtenue par les k-means et la carte de Kohonen. La thermographie infrarouge a été étudiée selon ses deux formes passive et active, les méthodes ultrasonores ont été exploitées en termes d’amplitude et de vitesse des ondes longitudinales et des ondes de Lamb respectivement. Il a été montré que l’approche multitechnique adoptée dans ce travail est très intéressante pour obtenir un diagnostic complet sur l’état de santé du matériau au repos et sous différents niveaux de chargement mécanique en traction. Il s’est avéré aussi que l’aspect « complémentarité » entre les trois techniques était plus envisageable que celui de la « redondance ». La fusion des données a été utilisée pour avoir une prise de décision fiable, complète et plus crédible sur les différents mécanismes d’endommagement susceptibles d’apparaître dans un matériau CMP. Ceci n’a été possible que pour les deux techniques d’imagerie, le C-scan ultrasonore et la thermographie infrarouge. En conclusion, les résultats montrent que ces trois techniques sont potentiellement capables de qualifier l’état d’endommagement du matériau, mais qu’elles ne le quantifient pas de la même manièreThis innovative study consists to implement in the same experimental procedure three non destructive techniques simultaneously: acoustic emission, infrared thermography and ultrasonic waves for the characterization of damage in cross ply Polymer Composite Materials (PCM) [0/90]S. Each technique has demonstrated its potential to reveal the damage that depends on its intrinsic characteristics. Acoustic emission has been used in its classical form and coupled with a data classification obtained by k-means and Kohonen map. Infrared thermography has been studied using both passive and active forms, ultrasonic methods have been used by exploiting amplitude and velocity of longitudinal and Lamb waves respectively. It has been shown that the adopted multi-technique approach is veryinteresting to obtain a full diagnostic of the health state of the material before and after uniaxial mechanical loading. The “complementarity” aspect between the three used techniques is showed more interesting that “redundancy” aspect. The data fusion theory was used to have a reliable, comprehensive and credible decision about the different damage mechanisms may appear in PCM material. This has been possible only for the two imaging techniques, ultrasonic C-scan and infrared thermography. All in all, the results show that these three techniques are potentially able to describe the damage state of the material, but they don’t quantify it with the same manner
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Gluchko, Sergei. "Manipulation d’énergie thermique avec des ondes de surface électromagnétique aux échelles micro- et anoscopiques." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC075/document.
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Les phonons polaritons de surface (SPhPs) sont des ondes électromagnétiques de surface évanescentes générées par le couplage phonon-photon et se propageant le long d’une interface entre un milieu polaire (tel que SiO2 et SiC) et un diélectrique. Dans ce mémoire, nous nous intéressons à de possibles applications des SPhPs pour améliorer les performances thermiques des nanosystèmes, en focalisant leur énergie thermique avec des micro- et nanostructures, en réduisant leurs angles de diffraction à travers des ouvertures sub-longueur d’onde, et en démontrant leur émission thermique cohérente large-bande. Nous avons aussi effectué des mesures par microscopie spectrophotométrique infrarouge de micro-objets et démontré l’excitation thermique de modes de grandes longueurs de propagation dans un large domaine spectral. Nos résultats sont obtenus sur des bases à la fois théoriques, de simulations numériques et expérimentales. Ces travaux sont pertinents dans les domaines liés au transfert thermique, à l’optique infrarouge, au rayonnement thermique de champ proche, à la microscopie infrarouge, et à la polaritoniqueSurface phonon-polaritons (SPhPs) are evanescent electromagnetic surface waves generated by the phononphoton coupling and that propagate along the interface of a polar medium (such as SiO2 and SiC) and a dielectric one. In this work, we investigate possible applications of SPhPs for enhancing the thermal performance of micro- and nanoscale devices, focusing of thermal energy with micro-structures, decreasing the diffraction angles of infrared radiation on subwavelength apertures, and demonstrating broadband coherent thermal emission. We also perform infrared spectroscopy microscopy measurements of microscale objects and demonstrate long-range thermally excited surface modes in a broad frequency range. The results presented in this thesis can have possible applications in fields related to heat transfer, infrared optics, near-field thermal radiation, infrared microscopy, and polaritonics
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Bolat, Beldek Tugba. "Short Wave Infrared Camera Design And Focal Plane Analysis." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614150/index.pdf.
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The subject of this study is the design of a camera, which has maximum volume of 50 mm x 50 mm x 300 mm, using short infrared wavelength providing Rayleigh criteria. Firstly, the required flux per pixel has been calculated. Throughout these calculations, atmospheric losses have been obtained by MODTRAN program. Also signal to noise ratio has been examined at minimum and maximum integration time intervals. The focal length of the camera has been calculated as it receives 1 m resolution from 8 km distance. Moreover, the lens materials have been used as N-F2, LIF and BaF2 in this six lens system. The design has been done using ZEMAX optical design program and the performance of the system at focal plane was investigated by the help of Seidel aberrations, Modulation transfer Function (MTF), Spot diagram and Optical Path Difference (OPD) fan plot analyses.
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McCarron, Andrew, and Andrew McCarron. "Long Wave Infrared Scan Lens Design And Distortion Correction." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/621849.
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The objective of this Thesis is to design a scan lens for a long wave infrared laser marking system. The system is comprised of a laser source emitting a collimated beam coupled with a 14mm aperture dual axis galvanometer scanning system capable of scanning a range ± 11° (mechanical). Multiple scan lens options will be considered. Each scan lens will be optimized to maximize peak irradiance and operate at, or near, the diffraction limit over a 210x110 mm 'plus' shaped field. Unintended distortion evident in some lens designs and will be compensated for by developing equations that allowed the proprietary imaging algorithm to adjust the angle of the scanning mirror appropriately to achieve an undistorted image. The accuracy of the distortion correction will be within 1% of the shortest image dimension. Commercially available scan lenses are designed for generic scanning systems with no apriori knowledge of the imaging model and are typically available in arbitrary focal length increments. As a result, use of off the shelf scan lenses result in sub-optimal performance. This thesis presents background information on galvanometer based scanning systems followed by a review of classical scan lenses. The imaging application and systems constraints for the marking system are defined. The steps taken to design and optimize a conventional, aspheric, and F-Theta scan lens are described, and their performances are compared with respect to the design requirements. The Conventional scan lens coupled with a distortion correction equation was found to offer the best performance to cost ratio and was deemed the most appropriate lens for the marking system.
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Koerperick, Edwin John Boggess Thomas F. Prineas John P. "High power mid-wave and long-wave infrared light emitting diodes device growth and applications /." Iowa City : University of Iowa, 2009. http://ir.uiowa.edu/etd/304.
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Constantinou, Marios, Michael Gehde, and Ronald Dietz. "Emitter - Material – A complex system." Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-198230.
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Der Vortrag zeigt die Komplexität der Wechselwirkungen zwischen Infrarotstrahler und Werkstoff beim Infrarotschweißen von Kunststoffen auf. Hierfür werden die Haupteinflüsse auf die Strahler-Werkstoff-Wechselwirkungen beschrieben. Diese sind das Emissionsverhalten des Infrarotstrahlers und das Absorptionsverhalten des Kunststoffs. Der Einfluss der Infrarotstrahlerart (Quarzglasstrahler, Metallfolienstrahler) und von Füllstoffen (Ruß, Glasfasern) im Kunststoff wird näher betrachtet. Zudem enthält der Vortrag eine Empfehlung für die Vorgehensweise beim Infrarotschweißen von Kunststoffen, die Vor- und Nachteile des Fügeverfahrens und einen Einblick in aktuelle Forschungsaktivitäten auf dem Gebiet des Infrarotschweißens von Kunststoffen.
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Johnson, Jennifer Erin. "Remote sensing applications of uncooled long-wave infrared thermal imagers." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/johnson/JohnsonJ0812.pdf.
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The commercial development of microbolometer uncooled long-wave thermal infrared imagers in conjuncture with advanced radiometric calibration methods developed at Montana State University has led to new uses of thermal imagery in remote sensing applications. As a result of being uncooled, microbolometer imagers are notably lighter and cheaper than typical cooled imagers, making them ideal for remote sensing. Two novel uses are discussed in the work presented here. The first is the imaging of beehives in order to remotely determine the hive vitality. Bees thermally regulate their hives to a narrow range of temperatures that creates a thermal signature seen in thermal infrared images. For each of the hives imaged, frame counts (or the number of full frames of bees in each hive) were found by manual inspection. Linear regressions of the normalized frame counts of the hives were performed versus the measured hive thermal radiance values. The resulting plots showed a strong relationship between the normalized frame count and the mean radiance of each hive, particularly in images taken just prior to dawn. The second novel use was imaging vegetation exposed to large ground concentrations of CO ����� over a four-week period in summer for use in leak detection. A CO ����� leak was simulated in a test field run by the Zero Emissions Research and Technology Center. Thermal infrared images were acquired along with visible and near-infrared reflectance images of the exposed vegetation and healthy control vegetation. Thermal radiance statistics were measured and a regression was performed versus the day of the experiment. The infrared data were found to have a strong R ² value and clearly show the effect of the CO ����� on the vegetation. An additional regression was run on the infrared data combined with the reflectance data, and this was found to not add any unique information to the vegetation reflectance data. Both methods were found to independently indicate the potential of a CO ����� leak before it was detected visually.
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Zeng, Tianyi. "Long-wave infrared frequency combs based on quantum cascade lasers." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113922.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 93-105).
Ever since the invention of quantum cascade laser (QCL), the performance and the flexibility in design has made it a desirable source for a wide range of applications, such as trace-chemical sensing, health monitoring, frequency metrology, noninvasive imgaing and infrared countermeasures. The LWIR region (or mid-infrared region), roughly ranging from 2-20 [mu]m, is of particular importance to spectroscopy applications, since many molecular species have their strongest rotational-vibrational absorption bands in that area. Infrared laser spectroscopy began about 40 years ago and has been using a variety of different tunable laser-based sources, particularly lead salt diodes, color center lasers, difference frequency generation and optical parametric oscillators. The large tunabilitiy in the design (lasing frequency, tunability, power, material system, etc.) and the compactness in fabrication and packaging has made QCL an ideal source for laser-based spectroscopy. Traditional spectroscopy systems suffer from problems like large physical dimensions, long data-processing times and spectral resolution restrictions. Therefore the development of a simple, robust, compact and inexpensive optical source/system like QCL frequency combs can largely benefit spectroscopy systems. In the past few years, QCLs have proven to be able to form comb radiation in both LWIR and THz regions. And dual comb spectroscopy has been demonstrated using QCL frequency combs with very short acquisition time ([mu]s). The development of a broadband, high power, narrow linewidth and stable LWIR frequency comb based on quantum cascade laser is the key to realizing such broadband ultrafast spectrometer in the mid-infrared range. This thesis explores the design, fabrication and characterization techniques towards the development of LWIR QCL frequency comb devices for spectroscopic purposes. A complete wet etch epi-up fabrication process is reported, with preliminary results on the dry-etch technique to incorporate dispersion compensation strucutre and epi-down fabricaiton for high power CW mode QCL device. Formation of comb(-like) regime has been observed in two devices, with the Gires-Tournois Interferometer (GTI) mirror providing dispersion from the rear facet. In order to improve the comb performance of these devices, dispersion of the device is measured to provide essential information for the design of chirped top cladding for dispersion compensation. This thesis provides an important step towards the realization of a room temperature, broadband, CW mode LWIR QCL frequency comb device for spectroscopic purposes.
by Tianyi Zeng.
S.M.
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Koerperick, Edwin John. "High power mid-wave and long-wave infrared light emitting diodes: device growth and applications." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/304.
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High brightness light emitting diodes based on the InAs/GaSb superlattice material system have been developed for use in mid-wave and long-wave infrared optoelectronic systems. By employing a multiple active region device configuration, high optical output has been demonstrated from devices in the 3-5μm and 7-12μm spectral bands. Mid-wave infrared optical output in excess of 0.95mW/sr has been observed from 120×120μm2 devices with peak emission at 3.8μm, and nearly 160μW/sr has been measured from devices of the same size operating at 8μm. Larger devices (1×1mm^2) with output as high as 8.5mW/sr and 1.6mW/sr have been demonstrated with mid-wave and long-wave devices, respectively, under quasi-DC bias conditions.
The high switching speed inherent to small area light emitting diodes as well as potentially high optical output make these devices appealing candidates to improve upon the current state-of-the-art in infrared projection technology. Simulation of thermal scenes with wide dynamic range and high frame rates is desirable for calibration of infrared detection systems. Suitable projectors eliminate the need for observation of a live scene for detector calibration, thereby reducing costs and increasing safety. Current technology supports apparent temperature generation of up to approximately 800 Kelvin with frame rates of hundreds of frames per second; strong desire exists to break these barriers.
Meeting the requirements of the aforementioned application requires development of the InAs/GaSb superlattice material system on multiple levels. Suppressing parasitic recombination channels via band structure engineering, improving carrier transport between active regions and confinement within active regions, reduction of defect-assisted recombination by optimizing device growth, and improving device fabrication and packaging are all routes requiring exploration. This work focuses on the latter two components of the optimization process, with emphasis on molecular beam epitaxial growth of high quality devices. Particular attention was paid to tailoring devices for thermal imaging applications and the design tradeoffs and limitations which impact that technology. Device performance and optimization success were gauged by electronic, optical, morphological, and structural characterization.
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Chanda, Geoffrey. "Terahertz and infrared spectroscopy of novel superconductors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-157061.
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The present thesis is devoted to the investigation of novel superconductors by phase-sensitive terahertz transmission and infrared to ultraviolet spectroscopy. In particular, a nominally undoped Pr2CuO4 superconducting thin film, an FeTe0.5Se0.5 thin film, and a LiFeAs single crystal have been investigated. The emphasis is on the low-frequency part of the optical spectrum (i.e., the terahertz and infrared spectrum), as the goal of the study was to shed light on the size and symmetry of the superconducting gaps and also to determine the temperature dependences as well as the absolute values of the penetration depth, which are key input parameters for models applicable for new superconductors. In addition, niobium has been investigated as a reference, so as to see what is expected from conventional superconductors and to clarify the electrodynamics of niobium.
A superconducting Nb thin film with Tc of 8.04 K has been investigated by backward wave oscillator-based (BWO-based) and time-domain terahertz (TDT) spectrometers in the frequency range between 4 and 100 cm−1 for temperatures ranging from 2 to 10 K. From these measurements an energy gap of 22.50 cm−1 = 2.79 meV = 4.02kBTc have been determined. The optical conductivity below Tc could nicely be described by calculations according to the Eliashberg theory, with the electron-phonon interaction evaluated from tunneling measurements.
Absolute values of the penetration depth have been calculated from phase-sensitive terahertz measurements. The zero-temperature limit of at T = 0 is found to be 115 ± 5 nm. From this value, a London penetration depth of 43 ± 2 nm has been obtained. The overall temperature dependence of the penetration depth follows a behavior typical for conventional s-wave superconductors.
A superconducting Pr2CuO4 film with T0 structure and Tc of 27 K has been investigated by use of optical methods in a wide frequency (5 – 55000 cm−1) and temperature (2 – 300 K) range. A Drude-like peak centered at zero frequency is observed in the optical conductivity below 150 K, above which it shifts to finite frequencies. The detailed analysis of the low-frequency conductivity reveals that the Drude peak and a far-infrared (FIR) peak centered at about 300 cm−1 persist at all temperatures. The FIR spectral weight is found to grow at the expense of the Drude spectral weight with increasing temperature. Absolute values of the penetration depth have been obtained from temperature and frequency-dependent measurements. The zero-temperature limit of is estimated to be 1600 ± 100 nm. The overall temperature dependence of follows a behaviour typical for cuprate superconductors. However, a closer look at the penetration depth at T 12 K reveals a flattening in the temperature dependence.
A superconducting FeTe0.5Se0.5 thin film with Tc = 19 K has been investigated using a combination of BWO and TDT spectroscopy in the frequency range 4 - 80 cm−1 and between 3 and 150 K. From such measurements, a superconducting energy gap of 30 cm−1, representing a coupling strength = 2.27, is observed. Further, the penetration depth has been derived from the temperature dependence of the imaginary part of complex conductivity with the penetration depth = 530 ± 10 nm at lowest measured temperature. The temperature-dependent normalized superfluid density, just as is the case with most iron-based superconductors, could nicely be described by the so-called two-gap gamma model.
Finally, a superconducting LiFeAs single crystal with Tc = 18 K has been investigated by optical spectroscopy in the frequency range 15 - 55000 cm−1 between 5 and 300 K. From these measurements, no clear signature of the superconducting energy-gap opening could be identified in spite of the spectral weight been suppressed in the infrared frequency regime below Tc. This indicates that LiFeAs single crystal is in a clean limit. With the aid of the Ferrell-Glover-Tinkham (FGT) sum rule, an absolute penetration depth of 215 nm has been calculated from the missing area at 5 K.
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Hill, Stephen. "Far-infrared and millimetre wave magneto-optical studies of interacting quasiparticles." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260147.
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Abdel, Rahman Mohamed. "ANTENNA-COUPLED TUNNEL DIODES FOR DUAL-BAND MILLIMETER-WAVE/INFRARED F." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2597.
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The infrared and millimeter-wave portions of the spectrum both have their advantages for development of imaging systems. Because of the difference in wavelengths, infrared imagers offer inherently high resolution, while millimeter-wave systems have better penetration through atmospheric aerosols such as fog and smoke. Shared-aperture imaging systems employing a common focal-plane array that responds to both wavebands are desirable from the viewpoint of overall size and weight. We have developed antenna-coupled sensors that respond simultaneously at 30 THz and at 94 GHz, utilizing electron-beam lithography. Slot-antenna designs were found to be particularly suitable for coupling radiation into metal-oxide-metal (MOM) tunnel diodes at both frequencies. The MOM diodes are fabricated in a layered structure of Ni-NiO-Ni, and act as rectifying contacts. With contact areas as low as 120 nm × 120 nm, these diodes have time constants commensurate with rectification at frequencies across the desired millimeter-wave and infrared bands. One challenge in the development of true focal-plane array imagers across this factor-of-300 bandwidth is that the optimum spatial sampling interval on the focal plane is different in both bands. We have demonstrated a focal plane with interleaved infrared and millimeter-wave sensors by fabricating infrared antennas in the ground plane of the millimeter-wave antenna. Measured performance data in both bands are presented for individual antenna-coupled sensors as well as for devices in the dual-band focal-plane-array format.Ph.D.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
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Middleton, Charles. "ANTENNA-COUPLED INFRARED AND MILLIMETER-WAVE DETECTORS: FABRICATION, MEASUREMENT AND OPTIMIZATION." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2598.
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Antenna-coupled detectors provide uncooled, cost-effective solutions for infrared and millimeter-wave imaging. This work describes the design, fabrication, measurement, and optimization of several types of antenna-coupled detectors for LWIR (8 - 12 µm) and 94 GHz radiation. Two types of millimeter-wave antenna-coupled detectors were fabricated and tested: a slot antenna coupled to a bolometer, and a patch antenna coupled to a SiC Schottky diode. Electromagnetic modeling of the antennas helped guide the design of antennas with better impedance matching to the detectors. Schottky diodes are discussed as detectors for millimeter-wave and infrared radiation, with the goal of increasing the cutoff frequency to allow infrared detection. The magnitude of response of antenna-coupled bolometric detectors to infrared radiation is affected by the thermal-conduction properties of the sensor structure. Two fabrication processes were developed to improve the thermal isolation of the antenna-coupled bolometer from its substrate. The first process creates a membrane beneath the device. Measured results show a factor of 100 increase in responsivity over an identical device without a membrane. The second process thermally isolates the device from its substrate by suspending the metallic structure in air. Several factors for optimization of infrared antenna-coupled detectors are investigated. The complex dielectric function of the metal from which the antenna is constructed can affect the performance of the device. The use of a ground plane and dielectric standoff layer beneath the antenna can increase the sensor responsivity. Dielectric material properties and thicknesses are considered, and incorporated in device simulations. Finally, a potential fabrication process is presented for via connections from the antenna-coupled detector through a ground plane to bond pads to mitigate the effect of bias lines on antenna behavior.Ph.D.
Other
Optics and Photonics
Optics
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Wabby, Anas. "Design and development of techniques in infrared and millimetre-wave imaging." Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408201.
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Xiang, Hengyang. "Colloidal nanocrystals applied for short-wave infrared photodetectors with fast response." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS423.
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L'infrarouge à ondes courtes (SWIR) désigne généralement les photons dans la plage de longueurs d'onde allant de 1 à 3 micromètres. Les applications dans cette fenêtre de longueur d'onde exploitent divers avantages tels qu’une grande longueur de pénétration dans le tissu biologique, la couverture spectrale pour la vision nocturne atmosphérique et l'énergie d'excitation caractéristique de certains modes de vibration moléculaire. Les photodétecteurs SWIR sont donc les composants technologiques essentiels pour la communication optique, la détection de gaz dans l’environnement, le biodiagnostic et la vision nocturne passive. Les technologies SWIR actuelles reposent principalement sur des semi-conducteurs composés à faible bande interdite, tels que InGaAs, InSb, PbS et HgCdTe. Alors que les photodétecteurs SWIR classiques présentent une excellente détectivité, ils sont coûteux (en raison de la croissance requise par l'épitaxie) et / ou présentent un risque environnemental car impliquant des éléments hautement toxiques. Par conséquent, des efforts continus en matière de recherche et de développement concernant des systèmes de matériaux alternatifs et des méthodes de fabrication permettant d'élargir le champ des applications de la photodétection SWIR sont en cours. Ces dernières années, de nombreux nouveaux matériaux ont été proposés, notamment les nanocristaux de phosphore noir, de graphène, de MoS2 et de PbS colloïdal. Ils sont très prometteurs en termes de fonctionnement à des fréquences de modulation élevées et avec une excellente sensibilité. Cependant, certains inconvénients les éloignent toujours du marché: processus de production difficile (faible reproductibilité), non-adaptabilité à la fabrication à grande échelle, préoccupations de sécurité lors de la production en usine (en raison de l’utilisation d’éléments hautement toxiques). Alternativement, les nanoparticules colloïdales traitées en solution, telles que les nanorods d’or colloïdal (Au NR) et les nanoparticules fonctionnant par up-conversion (UCNP), présentent des caractéristiques intéressantes permettant de surmonter ces inconvénients: capacité de synthèse et de production à grande échelle et à faible coût, haute stabilité, faible toxicité biologique et bonne absorption optique des photons SWIR. Cette thèse a pour objectif d'appliquer ces nanoparticules colloïdales à la fabrication de photodétecteurs SWIR et d’étudiere des possibilités d’application dans le domaine de la photodétection. Quelques photodétecteurs SWIR (Au-NRs / Thermistance, photodétecteur Au-NRs / Pt et photodétecteur UCNPs / Polymers) ont été développés dans ce travail, montrant une sensibilité élevées. De plus, la fabrication de ces dispositifs est un procédé peu coûteux et évolutif vers la production de masse au niveau de la fois à la synthèse des matériaux et de la fabrication des composants, et ouvre une nouvelle voie sur le marché de la prochaine génération de photodétecteursShort-wave infrared (SWIR) typically refers to the photons in the wavelength range from 1 to 3 micrometers. Applications in this wavelength window exploit various advantages such as long penetration length in biological tissue, spectral coverage of the atmospheric nightglow, and the characteristic excitation energy of certain molecular vibration modes. SWIR photodetectors are thus the key technological components to achieve optical communication, environmental gas sensing, biodiagnostics, and passive night vision. Current SWIR technologies mainly rely on low-bandgap compound semiconductors, such as InGaAs, InSb, PbS, and HgCdTe. While classical SWIR photodetectors exhibit excellent detectivity, they are costly (due to epitaxial growth requirement) and/or environment unfriendly involving highly toxic elements. There are, therefore, continuous research and development efforts for alternative material systems and fabrication methods to expand the scope of applications of SWIR photodetection. In recent years, many new materials have been proposed, including black phosphorus, graphene, MoS2, and colloidal PbS nanocrystals. They show great promise in terms of operation at high modulation frequencies or high sensitivity. But some disadvantages still keep them away from the market: rigorous production process (poor reproducibility), non-adaptability to scale-up fabrication, manufactory safety and security concerns (due to the use of highly toxic elements). Alternatively, solution-processed colloidal nanoparticles, such as colloidal gold nanorods (Au NRs) and upconversion nanoparticles (UCNPs), exhibit interesting characteristics possible to overcome these disadvantages: capability of scaling-up synthesis, solution-processability adaptable to low-cost fabrication, high stability, low biological toxicity, and good optical absorption for SWIR photons. This PhD thesis aims to apply these colloidal nanoparticles to fabricate SWIR photodetectors and verifies their possibilities for new generation of photodetection. A few SWIR photodetectors (Au-NRs/Thermistor, Au-NRs/Pt photodetector and UCNPs/Polymers photodetector) were developed in this work, showing high responsivity and sensitivity. In addition, the preparation of these devices is a low-cost and scalable up to mass production process both in the materials synthesis and device fabrication, opening a new and convenient path to the next-generation SWIR photodetectors
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La, Rosa Henrry. "Investigation of a Rectenna element for infrared and millimeter wave application." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002221.
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Smith, Mark William. "Design, construction, and calibration of a portable short wave infrared spectroradiometer." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185990.
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This dissertation describes the design, construction, and calibration of a portable short wave infrared (SWIR) spectroradiometer. The main use for the instrument is the collection of ground reflectance and radiance data for the radiometric calibration of operational and proposed high spectral resolution remote-sensing systems, such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS), the Moderate Resolution Imaging Spectroradiometer (MODIS), the High Resolution Imaging Spectrometer (HIRIS), and the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER). The instrument will also be used for cross calibrating Earth Observing System (EOS) calibration facilities and for a variety of high spectral resolution studies in earth science. The instrument is designed to be carried as a backpack unit, on a vehicle, or in a helicopter or airplane. The spectroradiometer covers the range from 1.05 to 2.45 μm. The spectral sampling interval is 1.37 nm and the spectral resolution is variable from about 5 nm to more than 100 nm. A single spectrum can be acquired in as little as 1 s. The signal-to-noise ratio (SNR) for a single 1-s scan is about 90 at a wavelength of 2.2 μm for a lambertian surface of 100% reflectance illuminated by the sun at normal incidence with 14-nm spectral resolution, a 25° background temperature, and no atmospheric attenuation. The SNR can be improved by averaging multiple scans. Field-of-view defining optics are coupled by a flexible fiber optics bundle to the spectroradiometer, which consists of a non-scanning concave holographic diffraction grating with flat focal field imaged onto a 1024-element liquid-nitrogen-cooled PtSi linear-array detector. The combination of concave grating and linear-array detector was chosen in preference to Fourier transform, Hadamard transform, and scanned grating monochromator systems on the basis of simplicity, high SNR, and greatest radiometric accuracy.
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Garden, Rognvald Peebles. "An infrared and millimeter-wave spectroscopic study of the DR21 outflow." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/28084.
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In this thesis, new high-angular resolution infrared and millimeter-wave spectroscopic observations of the enigmatic outflow activity associated with the luminous DR21 star-form ing region are presented and discussed. The intent is to use these observations to undertake a detailed investigation of the physical nature of the central driving engine and the related dynamical processes involved in collimating the hypersonic outflow gas. In the infrared, large-scale mapping and high-spectral resolution profile measurements of the vibrational H2 v = l-0 S(l) line are used to investigate the morphology and kinematic structure of the hot, dense gas that is collisionally excited behind fast shocks. The H2 emission delineates a highly-collimated pair of bipolar jets that extend over a projected distance of ~ 5 pc, centred on the DR21 molecular cloud core; this is undoubtedly the most luminous (in H2 line emission) and extended galactic outflow source yet discovered. Furthermore, the H2 line profiles at certain locations within the jets possess high-velocity wings that extend to beyond 100 km s-1 from the DR21 rest velocity. These observations pose interesting dynamical consequencies as at such high velocities H 2 should be entirely dissociated. In an attempt to derive the mass distribution and velocity structure of the molecular gas participating in the outflow, and hence the driving force and associated mechanical luminosity, detailed observations were also undertaken at millimeter-wavelengths in the CO J= 1 -0 and CS J = l-0 , J= 2-l lines. It is found that the DR21 outflow is considerably more massive and energetic than any other outflow source studied to date. Another feature unique to the DR21 region is the discovery of extended high-velocity CS emission that is dynamically associated with the outflow lobes and extends to a distance of ~ 3 pc from the cloud core; this component presumably originates from am bient gas that has been swept up and compressed by the outflow. The high-velocity CS may be overabundant by 2 orders of magnitude, in good agreement with current numerical models of post-shock chemistry. The CS observations further reveal the existence of an extremely massive, slowly rotating disc of high-density neutral gas that surrounds the central outflow source. It is most probable that the large momentum flux in outflow material derives from efficient mass-loss from the surface of this disc, mediated via a centrifugally propelled, magneto-hydrodynamic wind. An additional confinment mechanism is required to collimate the outflow at large distances from the flow origin. If this confinment is primarily pressure driven, then sudden changes in the ambient cloud pressure could induce a succession of oblique shocks within the outflow that may give rise to the periodic clumpy structure that characterizes the H2 emission-line jets. Other consequencies of the pressure-confinment mechanism are discussed and a broad resemblance to extragalactic radio jets is remarked upon.
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Smith, Daniel Gene. "High Dynamic Range Calibration for an Infrared Shack-Hartmann Wavefront Sensor." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194779.
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Since its invention in the early seventies, the Shack-Hartmann wavefront sensor has seen a wide variety of applications and has had great success in the fields of Adaptive Optics and Ophthalmology, where interferometry is usually impractical. Its application to optical shop testing has been less visible perhaps because shop environments can be manipulated to sufficiently remove vibration and turbulence to a degree that can support interferometry. However, with the growing need to accurately test aspheric optics, the Shack-Hartmann has an advantage; its dynamic range can be manipulated through the design of the lenslet array, rather than being directly tied to the wavelength of light and therefore lessen the need for expensive null optics.When the Shack-Hartmann is pushed to the limits of dynamic range, several issues must be dealt with. First, to reach the limits of dynamic range, those limits must be well understood. This dissertation presents a graphical approach to designing the Shack-Hartmann sensor that makes the trade-off between sensitivity and dynamic range, and accuracy and resolution intuitively clear. Next, the spots that once landed neatly in the region behind each lenslet, may now wander several lenslets away and the data reduction must be able handle this. This dissertation presents a novel and robust method for sorting these widely wondering spots and is shown to work in measurements of highly aspheric elements. Finally, in the high dynamic range regime, induced aberrations can severely limit the accuracy of the instrument. In this dissertation, these non-linear and measurement-dependent errors are studied in detail and a method of compensation is presented along with experimental results that illustrate the efficacy of the approach.
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Mares, Aimee Gail. "Remotely sensed density measurements of volcanic sulfur dioxide plumes using a spectral long wave infrared imager." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Sep%5FMares.pdf.
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Thesis (M.S. in Space Systems Operations)--Naval Postgraduate School, September 2002.Thesis advisor(s): Richard C. Olsen, Paul G. Lucey. Includes bibliographical references (p. 123-125). Also available online.
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Samanta, Goutam Kumar. "High-power, continuous-wave optical parametric oscillators from visible to near-infrared." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/29963.
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This thesis presents the development of a new class of high-power, continuous-wave (cw) optical parametric oscillators (OPOs) with extended tunability from visible to near-infrared (near-IR). While lasers have been in use for nearly 50 years, it is still difficult to develop laser systems that can cover many regions of the optical spectrum, from ultraviolet (UV) and visible to the near and mid-infrared wavelength range, with potential applications in the fields such as spectroscopy, remote sensing, trace gas detection, and many more.
Development of cw OPOs in singly-resonant oscillator (SRO) configurations, the focus of this thesis, is challenging due to the high threshold pump power (several watts). In addition, with visible pumping, photorefractive effect and thermal lensing effects become important issues to overcome. Therefore, the realization of practical cw SROs requires optimal cavity design, suitable nonlinear materials, and high-power laser with high spectral and spatial quality.
High-power, single-frequency, cw SROs based on 30-mm-long MgO-doped, stoichiometrically grown, periodically-poled LiTaO3 (MgO:sPPLT) have been developed. The oscillators were pumped in the green by a frequency-doubled cw diode-pumped Nd:YVO4 laser at 532 nm. With a single grating period of 7.97 µm, continuous signal and idler coverage over 848-1430 nm is obtained by temperature tuning between 52 oC and 248 oC. In a linear cavity configuration and double-pass pumping, an oscillation threshold of 2.88 W has been obtained, and single-pass idler powers in excess of 1.51 W have been generated over 1104-1430 nm for 6 W of pump power at an extraction efficiency of 25.2% and photon conversion efficiency of 56.7%.
For single-frequency performance of the cw SRO across 848-1430 nm, we have used a compact ring cavity configuration along with a frequency selecting element (etalon). Using the same MgO:sPPLT crystal, the SRO oscillation threshold of 2.84 W has been obtained, and single-pass idler powers in excess of 1.59 W have been generated over 1104-1430 nm with a maximum SRO extraction efficiency of 25.2% and pump depletions as much as 67%. The single-frequency idler output has a linewidth of ~7 MHz. Under free-running conditions and in the absence of thermal isolation, the idler power exhibits a peak-to-peak stability of 16% over 5 hours.
Although the cw SRO can provide optical radiation across 848-1430 nm, the high output power was only available over 1104-1430 nm, due to the high reflectivity of the cavity mirrors for SRO operation. Using finite output coupling of the resonant wave, we have extended the available practical output power across the entire tuning range. The cw out-coupled SRO (OC-SRO) can deliver total power of up to 3.6 W at 40% extraction efficiency with a linewidth of 3 MHz across 848-1430 nm. The signal power shows a peak-to-peak power stability <10.7% over 40 minutes in a TEM00 spatial mode with M2 <1.52. Without any active stabilization, the resonant signal exhibits a natural long-term frequency stability <75 MHz over 15 minutes and short-term frequency stability <10 MHz over 10 seconds, demonstrating the potential of the system for spectroscopic applications.
Using internal second-harmonic-generation of the resonant near-infrared signal radiation of the MgO:sPPLT cw SRO in a 5-mm-long BiB3O6 crystal, we have generated 1.27 W of cw, single-frequency blue power over a tunable range of 425-489 nm with a linewidth of 8.5 MHz and a Gaussian spatial beam profile. The blue source is frequency-stable to better than 280 MHz, limited by the resolution of the wavemeter.
We have also developed cw green sources, in a simple single-pass experimental configuration by frequency-doubling a fiber laser using MgO:sPPLT and periodically-poled KTiOPO4 (PPKTP) crystals, generating as much as 9.6 W of green radiation in TEM00 spatial beam profile (M2 <1.33) with a single-pass efficiency of 32.7% in MgO:sPPLT. This green source has also successfully been used to pump cw SROs and will be used to pump Ti:sapphire lasers.
Using this frequency-doubled green source, we have demonstrated cw OC-SRO providing a stable single-frequency output power up to 2 W across the tuning range of 855-1408 nm, with peak-to-peak power stability <11.7%, frequency-stability <10 MHz over 10 seconds, in TEM00 (M2 <1.26) spatial beam profile.Esta tesis presenta el desarrollo de una nueva clase de osciladores ópticos paramétricos (OPOs) de onda continua (cw) y alta potencia con extendida sintonización desde el visible al infrarrojo (IR) cercano. A pesar de que los láseres están en uso desde hace casi 50 años, todavía es difícil desarrollar sistemas láser que puedan cubrir muchas regiones del espectro óptico en los rangos de longitud de onda desde el ultravioleta (UV) y visible hasta el infrarrojo cercano y medio, con potenciales aplicaciones en campos como la espectroscopia, sensores remotos, detección de trazas de gases, entre muchas otras. El desarrollo de cw OPOs en configuraciones de oscilador simplemente resonante (SRO), objetivo principal de esta tesis, es un gran desafío debido al alto umbral de potencia de bombeo (varios watts). Además, cuando se emplea bombeo visible, los efectos fotorrefractivo y de lente térmica adquieren especial relevancia y son difíciles de superar. Por lo tanto, la realización de cw SROs prácticos requiere de un óptimo diseño de cavidad, adecuados materiales no lineales y láseres de alta potencia con excelente calidad tanto espectral como espacial. Se han desarrollado cw SROs de alta potencia y frecuencia única basados en cristales de LiTaO3 de 30 mm de longitud, de crecido estequiométrico, con dopado de MgO y periódicamente pulidos (MgO:sPPLT). Los osciladores fueron bombeados en el verde mediante el láser de cw Nd:YVO4 bombeado por diodos y doblado en frecuencia. Utilizando un único periodo de red de 7.97 m, se ha obtenido cobertura continua de los campos señal y pivote en el rango 848-1430 nm por sintonización de temperatura entre 52ºC y 248ºC. Empleando una configuración de cavidad lineal y bombeo de doble paso, se ha logrado un umbral de oscilación de 2.88 W y se han generado potencias superiores a 1.51 W para el campo pivote en simple paso dentro del rango 1104-1430 nm para 6 W de potencia de bombeo, eficiencia de extracción del 25.2% y eficiencia de conversión de fotón del 56.7%. Con el objetivo de operar el cw SRO en frecuencia única a través del rango 848-1430 nm, hemos utilizado una configuración compacta de cavidad en anillo junto a un elemento para la selección de frecuencia (etalon). Utilizando el mismo cristal de MgO:sPPLT, se ha obtenido un umbral de oscilación del SRO de 2.84 W y se han generado potencias superiores a 1.59 W para el campo pivote en paso único dentro del rango 1104-1430 nm con una eficiencia máxima de extracción del 25.2 % y agotamiento del bombeo tan alto como el 67%. La salida del campo pivote en frecuencia única tiene un ancho de línea de ~ 7 MHz. Bajo condiciones de sistema libre y en ausencia de aislamiento térmico, la potencia del campo pivote exhibe estabilidad de pico a pico de 16% durante 5 horas. A pesar de que el cw SRO puede proveer radiación óptica en el rango 848-1430 nm, la alta potencia de salida solo se consiguió obtener en el rango 1104-1430 nm a causa de la alta reflectividad de los espejos de la cavidad para operar en SRO. Utilizando un acoplamiento de salida finito de la onda resonante, hemos extendido la disponibilidad de prácticas potencias de salida a través de todo el rango de sintonía. El cw SRO con acoplador de salida (OC-SRO) puede entregar un apotencia total de hasta 3.6 W con una eficiencia de extracción del 40% y con un ancho de línea de 3 MHz en el rango 848-1430 nm. La potencia del campo señal muestra fluctuaciones en potencia de pico a pico <10.7% durante 40 minutos y modo espacial TEM00 con M2<1.52. En ausencia de estabilización activa, el campo señal resonante exhibe una estabilidad en frecuencia natural a largo término con fluctuaciones <75 MHz durante 15 minutos, así como a corto término con fluctuaciones<10MHz durante 10 segundos, demostrando el potencial del sistema para aplicaciones en espectroscopia. Utilizando generación interna de segundo harmónico del campo señal resonante en el rango del infrarrojo cercano del MgO:sPPLT cw SRO mediante un cristal de BiB3O6 de 5 mm de longitud, hemos logrado generar 1.27 W de potencia cw y frecuencia única en el azul dentro del rango de sintonía 425-489 nm y con un ancho de línea de 8.5 MHz y un perfil espacial del haz de tipo Gaussiano. La estabilidad en frecuencia de la fuente azul es mejor que 280 MHz, donde la limitación viene impuesta por la resolución del medidor de longitud de onda empleado. Adicionalmente, hemos desarrollado fuentes verdes en cw en una sencilla configuración experimental de único paso, mediante el doblado en frecuencia de un láser de fibra con cristales de MgO:sPPLT y KTiOPO4 pulido periódicamente (PPKTP), generando hasta 9.6 W de radiación verde en modo espacial TEM00 (M2<1.33) con una eficiencia de paso único de 32.7% en MgO:sPPLT. Esta fuente verde has sido también empleada exitosamente para bombear cw SROs y será utilizada para bombear láseres de Ti:sapphire. Mediante esta fuente verde doblada en frecuencia, hemos demostrado que el cw OC-SRO proporciona una salida estable en frecuencia única con potencia de hasta 2 W a través del rango de sintonía 855-1408 nm, con estabilidad en potencia de pico a pico <11.7%, estabilidad en frecuencia <10 MHZ durante 10 segundos y modo espacial TEM00 (M2<1.26).
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Walmsley, Byron Alan. "Micromechanical investigation of MEMS-based short-wave infrared tunable Fabry-Perot filters." University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0188.
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[Truncated abstract] This study investigates the mechanical and physical properties of low-temperature (100-300 ?C) plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiNxHy) thin films for the fabrication of short-wave infrared tunable Fabry-Perot filters with high fill factor, high cavity finesse and low actuation voltages. It has been the intensions of this work to fabricate a tunable filter that can be monolithically integrated with temperature-sensitive substrates, namely mercury cadmium telluride (Hg(1-x)CdxTe) photoconductors and photodiodes. A range of methods have been utilised to determine the Young's modulus (E), residual stress ([sigma]0), density ([rho]) and Poisson's ratio ([nu]) of PECVD SiNxHy thin films. In order to understand how E, [sigma]0, [rho] and [nu] are affected by process conditions, a range of SiNxHy thin films deposited with varying chuck temperatures, RF powers and chamber pressures were measured. The resonance method was used to determine E and [nu] of SiNxHy thin films deposited under varying process conditions. The resonance method involves exciting the bending and torsional vibration modes of a microcantilever beam fabricated from a film. The E and G values can be extracted directly from the bending and torsional vibration modes and the [nu] value can be determined from the calculated E and G values. The density of the films was determined using the quartz crystal microbalance method. In order to determine the validity of the resonance method, finite element modelling was used to determine its dependence on microcantilever beam dimensions. ... Increasing the temperature also increases the tensile residual stress of the films. This study also reveals that increasing the RF power and decreasing the chamber pressure increases E and [rho], as well as increasing the compressive residual stress of the films. The theoretical design and analysis, as well as the fabrication of a new surface micromachined short-wave infrared tunable Fabry-Perot filter for adaptive infrared photon detectors is also presented in this study. The proposed structure, termed the suspension filter, uses broad spectral range, high reflectivity distributed Bragg reflector (DBR) mirrors, resulting in very high finesse filters. The device utilises multiple sacrificial layers to define the resonant cavity spacer and the separation of the top mirror from the supporting flexures. The flexures were fabricated from low-temperature (PECVD) SiNxHy thin films. Separation of the top mirror from the supporting flexures allows for improved fill-factors (up to 79%), as well as increased tuning range. Theoretical optical and electromechanical results shows large wavelength tuning ranges (1.5-2.5 [mu]m) at low actuation voltages (<30 V) are possible using the proposed design, whilst still maintaining a high cavity finesse. Optical characterisation of fixed filter micro-cavities on Si substrates show transmissions of ~60% with small line widths (35 nm) are achievable using the proposed mirror system. Mirror displacement versus applied bias voltage curves obtained from a released filter fabricated on Si show a stable mirror displacement of 620 nm was achieved, whilst theoretical results suggested the required 750 nm mirror displacement is possible using the proposed design.
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Du, Bosq Todd. "FAR-INFRARED/MILLIMETER WAVE SOURCE AND COMPONENT DEVELOPMENT FOR IMAGING AND SPECTROSCOPY." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3101.
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The far-infrared and millimeter wave (FIR/mmW) (wavelength 75 micrometer to 10 mm) portion of the electromagnetic spectrum is fairly underdeveloped technologically, owing to the large amount of atmospheric attenuation in that range. At present, the FIR/mmW region is lacking in compact, high-brightness radiation sources and practical imaging systems. This dissertation focuses on development of two complementary technologies in this area – an active mmW imaging system and high-reflectivity Bragg mirrors for the FIR p-Ge laser. The imaging system uses a vector network analyzer in the frequency range of 90-140 GHz as the radiation source and receiver. Raster scanning is used to map a two-dimensional field of view, demonstrating the detection and imaging of buried plastic landmines. Principal components analysis is used for hyperspectral signal processing, where a series of images is taken at discrete frequencies. Results are obtained as a function of depth and disturbance of the soil surface. In support of this study, various types of soils were characterized for scattering loss across the mmW/FIR region, with measured results compared to theory. This mmW imaging system was also used to demonstrate imaging through walls and other obscuring materials, as well as for imaging of rocks beneath volcanic sand, simulating the conditions encountered by an imaging system on a Mars rover vehicle. Furthermore, a high-reflectivity Si-etalon FIR mirror design was developed and demonstrated as a cavity mirror for the p-Ge laser. These components stand to have a number of systems-level impacts on FIR imagers. In the context of an active illuminator, they may allow narrowband selection from the broad emission spectrum of the p-Ge laser source. These mirrors can also be used in a Fabry-Perot FIR scanning spectrometer, where the resulting high finesse would give discrimination advantages in chemical sensing and astrophysical spectroscopy applications.Ph.D.
Department of Physics
Sciences
Physics PhD
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Dean, Andrew E. "Scanning and beam-forming techniques for passive infrared and millimetre-wave imaging." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394492.
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Schuh, K., M. Kolesik, E. M. Wright, J. V. Moloney, and S. W. Koch. "Self-Channeling of High-Power Long-Wave Infrared Pulses in Atomic Gases." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/623047.
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We simulate and elucidate the self-channeling of high-power 10 mu m infrared pulses in atomic gases. The major new result is that the peak intensity can remain remarkably stable over many Rayleigh ranges. This arises from the balance between the self-focusing, diffraction, and defocusing caused by the excitation induced dephasing due to many-body Coulomb effects that enhance the low-intensity plasma densities. This new paradigm removes the Rayleigh range limit for sources in the 8-12 mu m atmospheric transmission window and enables transport of individual multi-TW pulses over multiple kilometer ranges.
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Sun, Yu. "SIGNAL PROCESSING FOR SHORT WAVE INFRARED (SWIR) RAMAN SPECTROSCOPY DIAGNOSIS OF CANCER." Master's thesis, Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/446864.
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BioengineeringM.S.
Raman spectroscopy is an effective optical analysis of the biochemically specific characterization of tissues without contrast agents or exogenous dyes. Applications of Raman spectroscopy include analysis and biomarker investigation, disease diagnosis and surgical guidance. One major challenge in Raman spectroscopy is removing inherent fluorescence background present in samples to acquire Raman signatures. In some tissues, like liver, kidney and darkly pigment skin, the auto-fluorescence background is strong enough to overwhelm the Raman peaks in conventional Near-Infrared (NIR) Raman systems. Recent publications have shown that using Raman systems with excitation sources with wavelengths beyond 830 nm and short-wave infrared (SWIR) InGaAs Array detectors resulted in dramatically reduced auto-fluorescence. The unique characteristics of Raman signals collected from SWIR systems versus NIR Raman systems requires inspection of the suitability of spectral pre-processing techniques. This thesis focused on the development of spectral processing techniques at three different steps; 1) detector background & noise reduction; 2) Auto-fluorescence background subtraction; 3) detection of outlier measurements to assist statistical classification. Detector background and noise reduction was compared between two different techniques, and a direct subtraction method resulted in better performance to reduce fixed pattern noise unique to InGaAs arrays. For the aim 2, three different algorithms for fluorescence background removal were developed, and a modified polynomial fitting method was found to be most appropriate for the low signal-to-noise (SNR) spectra. Finally, local outlier factor(LOF), a multivariate statistical outlier metric, was implemented in a two-stage fashion, and shown to be effective at identifying raw measurement errors and Raman spectra outliers. The overall outcome of this thesis was the evaluation of spectral processing techniques for SWIR Raman spectroscopy systems, and the development of specific techniques to optimize data quality and best prepare spectra for statistical analysis.
Temple University--Theses
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Boynton, Ansel John. "EARLY WILDFIRE DETECTION USING TEMPORAL FILTERING AND MULTI-BAND INFRARED ANALYSIS." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1048.
Full textAbstract:
Every year wildfires threaten or destroy ecological habitats, man-made infrastructure and people’s lives. Additionally millions of dollars are spent each year trying to prevent and control these fires. Ideally if a wildfire can be detected before it rages out of control it can be extinguished and avoid large scale devastation. Traditional manned fire lookout towers are neither cost effective nor particularly efficient at detecting wildfire. It is proposed that temporal filtering can be used to isolate the signals created at the beginnings of potential wildfires. Temporal filtering can remove any background image and any periodic signals created by the camera movement. Once typical signals are analyzed, digital filters can be designed to pass fire signals while blocking the unwanted signals. The temporal filter passes only fire signals and signals generated by moving objects. These objects can be distinguished from each other by analyzing the objects mid and long wave energy profile. This algorithm is tested on 17 data sources and its results analyzed.
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Schuh, K., P. Rosenow, M. Kolesik, E. M. Wright, S. W. Koch, and J. V. Moloney. "Nonlinear rovibrational polarization response of water vapor to ultrashort long-wave infrared pulses." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/625977.
Full textAbstract:
We study the rovibrational polarization response of water vapor using a fully correlated optical Bloch equation approach employing data from the HITRAN database. For a 10-mu m long-wave infrared pulse the resulting linear response is negative, with a negative nonlinear response at intermediate intensities and a positive value at higher intensities. For a model atmosphere comprised of the electronic response of argon combined with the rovibrational response of water vapor this leads to a weakened positive nonlinear response at intermediate intensities. Propagation simulations using a simplified noncorrelated approach show the resultant reduction in the peak filament intensity sustained during filamentation due to the presence of the water vapor.