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Title: Far-infrared bands in plasmonic metal-insulator-metal absorbers optimized for long wave infrared.
Creator: Evans, Rachel, Peale, Robert, Ishigami, Masahiro, Lyakh, Arkadiy, University of Central Florida
Abstract / Description: Metal(-)insulator(-)metal (MIM) resonant absorbers comprise a conducting ground plane, a thin dielectric, and thin separated metal top-surface structures. Long-wave infrared (LWIR) fundamental absorptions are experimentally shown to be optimized for a ratio of dielectric thickness to top-structure dimension t/l (>) 0.08. The fundamental resonance wavelength is predicted by different analytic standing-wave theories to be ~2nl, where n is the dielectric refractive index. Thus, for the...
Show moreMetal(-)insulator(-)metal (MIM) resonant absorbers comprise a conducting ground plane, a thin dielectric, and thin separated metal top-surface structures. Long-wave infrared (LWIR) fundamental absorptions are experimentally shown to be optimized for a ratio of dielectric thickness to top-structure dimension t/l (>) 0.08. The fundamental resonance wavelength is predicted by different analytic standing-wave theories to be ~2nl, where n is the dielectric refractive index. Thus, for the dielectrics SiO2, AlN, and TiO2, l values of a few microns give fundamentals in the 8-12 micron LWIR wavelength region. Agreement of observed fundamental resonance wavelength with theory is better for t/l (>) ~0.2. Harmonics at shorter wavelengths are always observed, but we show that there are additional resonances in the far-infrared 20-50 micron wavelength range, well beyond the predicted fundamental. These appear to be due to dispersion. They may impact selectivity in spectral sensing applications.
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Date Issued: 2018
Identifier: CFE0007176, ucf:52267
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007176

Title: TRANSMISSION LINES FOR IR SIGNAL ROUTING.
Creator: Mandviwala, Tasneem, Boreman, Glenn, University of Central Florida
Abstract / Description: In this dissertation, the design, fabrication, and characterization of coplanar striplines, vias, and microstrip lines is investigated, from the point of view of developing interconnections for antenna-coupled infrared detectors operating in the 8- to 12-micron wavelength range. To our knowledge, no previous efforts have been made to study the performance of metallic-wire transmission lines at infrared frequencies. Both the design and fabrication of these structures present unique challenges....
Show moreIn this dissertation, the design, fabrication, and characterization of coplanar striplines, vias, and microstrip lines is investigated, from the point of view of developing interconnections for antenna-coupled infrared detectors operating in the 8- to 12-micron wavelength range. To our knowledge, no previous efforts have been made to study the performance of metallic-wire transmission lines at infrared frequencies. Both the design and fabrication of these structures present unique challenges. Because of attenuation and dispersion issues, the analytical formulas for transmission-line parameters that are valid below a few hundred GHz are not applicable in the infrared. Therefore, numerical modeling was performed to characterize the coplanar striplines and microstrip structures in terms of transmission-line parameters: characteristic impedance, attenuation constant and effective index of refraction. These parameters were extracted by fitting the computed impedance as a function of transmission-line length to the usual impedance transformation equation. The material properties used in the model are realistic, having been measured at the frequencies of interest by infrared ellipsometric techniques. The transmission-line parameters cannot be measured directly in the infrared, so experimental validation was carried out by measuring the response of a bolometer, which was connected to a dipole antenna by different lengths of both the coplanar and microstrip transmission lines. The modeled and measured responses for both types of transmission lines was in good agreement. A third type of signal-routing structure was also investigated, that of the vertical via, essentially a low-frequency connection that facilitates location of the bondpads away from the plane of the antenna. In the configuration studied, the vias pass vertically down through the SiO2 isolation layer and a groundplane, which provides electromagnetic isolation between the antenna and the structures that allow for signal-extraction from the bolometer. This type of interconnection will be useful for future detailed studies relating the angular antenna pattern to the spatial response of the antenna-coupled sensor.
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Date Issued: 2006
Identifier: CFE0001304, ucf:47025
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001304

Title: INFRARED THERMOGRAPHY AND HIGH ACCURACY GPS FOR AUTOMATED ASPHALT CRACK DETECTION.
Creator: Abdel-Monem, Tarek, Oloufa, Amr, University of Central Florida
Abstract / Description: Roads are major public assets. The USA spends billions of dollars each year on road construction and maintenance. To keep these roads in a healthy condition and for better planning and allocation of maintenance budgets, knowledge of distressed locations is needed. Roads develop cracks when they are subjected to stresses that exceed their designed criteria or their materials properties. Early detection and repair of cracks has proven to be the most cost-effective strategy in limiting the...
Show moreRoads are major public assets. The USA spends billions of dollars each year on road construction and maintenance. To keep these roads in a healthy condition and for better planning and allocation of maintenance budgets, knowledge of distressed locations is needed. Roads develop cracks when they are subjected to stresses that exceed their designed criteria or their materials properties. Early detection and repair of cracks has proven to be the most cost-effective strategy in limiting the damage to roads and reducing expenditures. Various methodologies of crack detection were developed and significant techniques were made in the last few years. One of the most important recent technologies is the infrared thermography, which allows the use of infrared waves for crack detection. Another important technology is the global navigation satellite system (GNSS) which currently includes the GPS and GLONASS constellations. With the help of these systems, accurate location coordinates (longitude, latitude and altitude) up to a few centimeters were located. The objective of this research is to test the combined use of GNSS and infrared thermography in an automated system for the detection of asphalt cracks and their locations. To achieve this goal, two tests have been conducted. The first one, regarding the location tagging, was done using two pairs of GPS receivers which can detect signals from both GPS and GLONASS navigation systems in single and dual frequencies (L1 and L2). Different modes have been set to the receiver and comparison graphs were developed to compare accuracies against modes. The second test involves an infrared camera mounted on a car and moving in speeds approaching highway speed limit. The images obtained from the camera were processed using cracks detection software to analyze cracks properties (length, width, density and severity). It was found that the images that were taken by a moving infrared camera were recognized by crack detection software for moving speeds up to 50 mph. At speeds higher than 50 mph, images were blurred. As for location test, The GLONASS combined by GPS receivers got slightly better results than GPS only in both dual and single frequencies. The GLONASS satellites are not always available in view and when they are there, the number of satellites that can be detected by receiver range from one to three satellites at the most and for only a short period of time. It is recommended that future research be conducted to investigate the effect of using different camera lenses on the clarity of the images obtained as well as the effect of raising the camera level above the pavement surface in such a way that the whole lane width (12 ft.) would be covered in one image. Also the total reliance on GPS only receivers in determining cracks location has proven to be enough for this application.
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Date Issued: 2005
Identifier: CFE0000668, ucf:46534
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000668

Title: Infrared Tapered Slot Antennas Coupled to Tunnel Diodes.
Creator: Florence, Louis, Boreman, Glenn, Likamwa, Patrick, Schoenfeld, Winston, Lail, Brian, University of Central Florida
Abstract / Description: Tapered slot antennas (TSAs) have seen considerable application in the millimeter-wave portion of the spectrum. Desirable characteristics of TSAs include symmetric E- and H-plane antenna patterns, and broad non-resonant bandwidths. We investigate extension of TSA operation toward higher frequencies in the thermal infrared (IR), using a metal-oxide-metal diode as the detector. Several different infrared TSA design forms are fabricated using electron-beam lithography and specially developed...
Show moreTapered slot antennas (TSAs) have seen considerable application in the millimeter-wave portion of the spectrum. Desirable characteristics of TSAs include symmetric E- and H-plane antenna patterns, and broad non-resonant bandwidths. We investigate extension of TSA operation toward higher frequencies in the thermal infrared (IR), using a metal-oxide-metal diode as the detector. Several different infrared TSA design forms are fabricated using electron-beam lithography and specially developed thin-film processes. The angular antenna patterns of TSA-coupled diodes are measured at 10.6 micrometer wavelength in both E- and H-planes, and are compared to results of finite-element electromagnetic modeling using Ansoft HFSS. Parameter studies are carried out, correlating the geometric and material properties of several TSA design forms to numerical-model results and to measurements. A significant increase in antenna gain is noted for a dielectric-overcoat design. The traveling-wave behavior of the IR TSA structure is investigated using scattering near-field microscopy. The measured near-field data is compared to HFSS results. Suggestions for future research are included.
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Date Issued: 2012
Identifier: CFE0004376, ucf:49395
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004376

Title: SURFACE PLASMON HOSTS FOR INFRARED WAVEGUIDES AND BIOSENSORS, AND PLASMONS IN GOLD-BLACK NANO-STRUCTURED FILMS.
Creator: Cleary, Justin, Peale, Robert, University of Central Florida
Abstract / Description: Applications of surface plasmon polaritons (SPPs) have thus far emphasized visible and near-infrared wavelengths. Extension into the long-wave infrared (LWIR) has numerous potential advantages for biosensors and waveguides, which are explored in this work. A surface plasmon resonance (SPR) biosensor that operates deep into the infrared (3-11 Ã‚Âµm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic...
Show moreApplications of surface plasmon polaritons (SPPs) have thus far emphasized visible and near-infrared wavelengths. Extension into the long-wave infrared (LWIR) has numerous potential advantages for biosensors and waveguides, which are explored in this work. A surface plasmon resonance (SPR) biosensor that operates deep into the infrared (3-11 Ã‚Âµm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic vibrational modes. The goal is to operate such sensors at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra and where the refractive index is increased by dispersion, which will provide enhanced selectivity and sensitivity. Potentially useful IR surface plasmon resonances are investigated on lamellar gratings formed from various materials with plasma frequencies in the IR wavelength range including doped semiconductors, semimetals, and conducting polymers. One outcome of this work has been the demonstration of a simple analytic formula for calculating the SPP absorption resonances in the angular reflectance spectra of gratings. It is demonstrated for Ag lamellar gratings in the 6-11 Ã‚Âµm wavelength range. The recipe is semi-empirical, requiring knowledge of a surface-impedance modulation amplitude, which is found here by comparison to experiment as a function of the grating groove depth and the wavelength. The optimum groove depth for photon-to-SPP energy conversion was found by experiment and calculation to be ~10-15% of the wavelength. Hemicylindrical prism couplers formed from Si or Ge were investigated as IR surface plasmon couplers for the biosensor application. Strong Fabry-Perot oscillations in the angular reflectance spectra for these high index materials suggest that grating couplers will be more effective for this application in the LWIR. A variety of materials having IR plasma frequencies were investigated due to the tighter SPP mode confinement anticipated in the IR than for traditional noble metals. First doped-Si and metal silicides (Ni, Pd, Pt and Ti) were investigated due to their inherent CMOS compatibility. Rutherford backscattering spectroscopy, x-ray diffraction, scanning electron microscopy, secondary ion mass spectrometry and four point probe measurements complemented the optical characterization by ellipsometry. Calculation of propagation length and mode confinement from measured permittivities demonstrated the suitability for these materials for LWIR SPP applications. Semimetals were also investigated since their plasma frequencies are intermediate between those of doped silicon and metal silicides. The semimetal antimony, with a plasma frequency ~80 times less than that of gold was characterized. Relevant IR surface plasmon properties, including the propagation length and penetration depths for SPP fields, were determined from optical constants measured in the LWIR. Distinct resonances due to SPP generation were observed in angular reflection spectra of Sb lamellar gratings in the wavelength range of 6 to 11 Ã‚Âµm. Though the real part of the permittivity is positive in this range, which violates the usual condition for the existence of bound SPP modes, calculations based on experimental permittivity showed that there is little to distinguish bound from unbound SPP modes for this material. The SPP mode decays exponentially away from the surface on both sides of the permittivity sign change. Water is found to broaden the IR plasmon resonances significantly at 9.25 micron wavelength where aqueous extinction is large. Much sharper resonances for water based IR SPR biosensor can be achieved in the 3.5 to 5.5 Ã‚Âµm range. Nano-structured Au films (Au-black) were investigated as IR absorbers and possible solar cell enhancers based on surface plasmon resonance. The characteristic length scales of the structured films vary considerably as a function of deposition parameters, but the absorbance is found to be only weakly correlated with these distributions. Structured Au-black with a broad range of cluster length scales appear to be able to support multiple SPP modes with incident light coupling to the corrugated surface as seen by photoelectron emission microscopy (PEEM) and SPR experiments, supporting the hypothesis that Au-black may be a suitable material for plasmon-resonance enhancement solar-cell efficiency over the broad solar spectrum.
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Date Issued: 2010
Identifier: CFE0003231, ucf:48547
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003231

Title: SPECTRAL SIGNATURE MODIFICATION BY APPLICATION OF INFRARED FREQUENCY-SELECTIVE SURFACES.
Creator: Monacelli, Brian, Boreman, Glenn, University of Central Florida
Abstract / Description: It is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive...
Show moreIt is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive microantenna elements to cover the surface in order to modify its signature. This technology is known as frequency selective surface (FSS) technology and is established in the millimeter-wave spectral regime, but is a challenging technology to scale for IR application. Incorporation of thin films and FSS antenna elements on a surface permits the signature of a surface to be changed in a deterministic manner. In the seminal application of this work, both technologies are integrated to comprise a circuit-analog absorbing IR FSS. The design and modeling of surface treatments are accomplished using commercially-available electromagnetic simulation software. Fabrication of microstructured antenna arrays is accomplished via microlithographic technology, particularly using an industrial direct-write electron-beam lithography system. Comprehensive measurement methods are utilized to study the patterned surfaces, including infrared spectral radiometry and Fourier-transform infrared spectrometry. These systems allow for direct and complementary spectral signature measurements--the radiometer measures the absorption or emission of the surface, and the spectrometer measures its transmission and reflection. For the circuit-analog absorbing square-loop IR FSS, the spectral modulation in emission is measured to be greater than 85% at resonance. Other desirable modifications of surface signature are also explored; these include the ability to filter radiation based on its polarization orientation and the ability to dynamically tune the surface signature. An array of spiral FSS elements allows for circular polarization conditioning. Three techniques for tuning the IR FSS signature via voltage application are explored, including the incorporation of a pn junction substrate, a piezoelectric substrate and a liquid crystal superstrate. These studies will ignite future explorations of IR FSS technology, enabling various unique applications.
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Date Issued: 2005
Identifier: CFE0000589, ucf:46471
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000589

Title: Processing of Advanced Infrared Materials.
Creator: Mcgill, Daniel, Richardson, Kathleen, Gaume, Romain, Christodoulides, Demetrios, Rivero Baleine, Clara, University of Central Florida
Abstract / Description: Infrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process,...
Show moreInfrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process, which uses a sacrificial pressure-transmitting medium, can be used to fully densify a 70TeO2-20WO3-10La2O3 (TWL) glass powder. The characteristics of the sintered TWL glass is compared to that of a parent glass produced through a conventional melt/quench process to ascertain the impact of process-specific property changes on the resulting material. Additionally, the design, construction and characterization of a custom-made transparent Bridgman crystal growth furnace is undertaken to enable growth of highly birefringent tellurium single crystal. The key obstacles that need to be overcome to scale up the size of the grown crystals are summarized with the end goal of producing commercial grade optical elements.
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Date Issued: 2019
Identifier: CFE0007894, ucf:52761
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007894

Title: INFRARED SURFACE PLASMON POLARITONS ON SEMICONDUCTOR, SEMIMETAL AND CONDUCTING POLYMER.
Creator: Shahzad, Monas, Peale, Robert, Heinrich, Helge, Coffey, Kevin, Diaz, Diego, University of Central Florida
Abstract / Description: Conductors with IR (infrared) plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPPs) with subwavelength mode confinement for sensing applications. The underlying aim of this work is to identify such conductors that also have sharp SPP excitation resonances for biosensor applications at infrared (3-11 ?m) wavelengths, where biological analytes are strongly differentiated by their IR absorption spectra. In this work, various materials were investigated such as a...
Show moreConductors with IR (infrared) plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPPs) with subwavelength mode confinement for sensing applications. The underlying aim of this work is to identify such conductors that also have sharp SPP excitation resonances for biosensor applications at infrared (3-11 ?m) wavelengths, where biological analytes are strongly differentiated by their IR absorption spectra. In this work, various materials were investigated such as a heavily doped semiconductor, a semimetal, a conducting polymer and its composite.Heavily doped silicon was investigated by tuning its plasma frequency to the infrared region by heavily doping. The measured complex permittivity spectra for p-type silicon with a carrier concentration of 6 (&)#215; 1019 and 6 (&)#215; 1020 cm-3 show that these materials support SPPs beyond 11 and 6 ?m wavelengths, respectively. SPP generation was observed in angular reflection spectra of doped-silicon gratings. Photon-to-plasmon coupling resonances, a necessary condition for sensing, were demonstrated near 10 ?m wavelength for the heaviest doped, and the observed resonances were confirmed theoretically using analytic calculations. The permittivity spectra were also used to calculate SPP mode heights above the silicon surface and SPP propagation lengths. Reasonable merit criteria applied to these quantities suggest that only the heaviest doped material has sensor potential, and then mainly within the wavelength range of 6 to 10 ?m. The semimetal bismuth (Bi) has an infrared plasmon frequency less than the infrared plasma frequency of noble metals such as gold and silver, which is one order of magnitude lower than their plasma frequencies. The excitation of IR surface plasmons on Bi lamellar gratings in the wavelength range of 3.4 (&)#181;m to 10.6 (&)#181;m was observed. Distinct SPP resonances were observed although the usual condition for bound SPP is not satisfied in this wavelength range because the real part of the permittivity is positive. The excitation of these resonances agrees theoretically with the electromagnetic surface waves called surface polaritons (SPs). The measured permittivity spectra were used to calculate the SP mode heights above the bismuth surface and SP propagation length, which satisfied our criteria for sensors.A conducting polymer and its composite with graphite were also investigated since their plasma frequency may lie in the infrared region. Polyaniline was chemically synthesized and doped with various acids to prepare its salt form. A composite material of polyaniline with colloidal and nano-graphite was also prepared. Optical constants were measured in the long wave infrared region (LWIR) and were used to calculate SPP propagation length and penetration depth. SPP resonance spectra were calculated and suggested that polyaniline and its composite can be used as a host with sufficient mode confinement for IR sensor application.
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Date Issued: 2012
Identifier: CFE0004598, ucf:49215
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004598

Title: INFRARED PHASED-ARRAY ANTENNA-COUPLED TUNNEL DIODES.
Creator: Slovick, Brian, Boreman, Glenn, University of Central Florida
Abstract / Description: Infrared (IR) dipole antenna-coupled metal-oxide-metal (MOM) tunnel diodes provide a unique detection mechanism that allows for determination of the polarization and wavelength of an optical field. By integrating the MOM diode into a phased-array antenna, the angle of arrival and degree of coherence of received IR radiation can be determined. The angular response characteristics of IR dipole antennas are determined by boundary conditions imposed by the surrounding dielectric or conductive...
Show moreInfrared (IR) dipole antenna-coupled metal-oxide-metal (MOM) tunnel diodes provide a unique detection mechanism that allows for determination of the polarization and wavelength of an optical field. By integrating the MOM diode into a phased-array antenna, the angle of arrival and degree of coherence of received IR radiation can be determined. The angular response characteristics of IR dipole antennas are determined by boundary conditions imposed by the surrounding dielectric or conductive environment on the radiated fields. To explore the influence of the substrate configuration, single dipole antennas are fabricated on both planar and hemispherical lens substrates. Measurements demonstrate that the angular response can be tailored by the thickness of the electrical isolation stand-off layer on which the detector is fabricated and/or the inclusion of a ground plane. Directional detection of IR radiation is achieved with a pair of dipole antennas coupled to a MOM diode through a coplanar strip transmission line. The direction of maximum angular response is altered by varying the position of the diode along the transmission line connecting the antenna elements. By fabricating the devices on a quarter wave layer above a ground plane, narrow beam widths of 35° full width at half maximum and reception angles of ± 50° are achievable with minimal side-lobe contributions. Phased-array antennas can also be used to assess the degree of coherence of a partially coherent field. For a two-element array, the degree of coherence is a measure of the correlation of electric fields received by the antennas as a function of the element separation.
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Date Issued: 2011
Identifier: CFE0003589, ucf:48926
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003589

Title: Non-Destructive Evaluation of Concrete Structures Using High Resolution Digital Image and Infrared Thermography Technology.
Creator: Watase, Azusa, Catbas, Fikret, Tatari, Mehmet, Nam, Boo Hyun, University of Central Florida
Abstract / Description: As existing bridge structures age, they are susceptible to the effects of deterioration, damage and other deleterious processes. These effects hamper the capacity and efficiency of transportation networks and adversely impact local, regional and national economic growth. As a result, bridge authorities and other professionals have become more sensitive to maintenance issues related to this aging infrastructure. While highway bridge condition have been monitored by visual inspection, non...
Show moreAs existing bridge structures age, they are susceptible to the effects of deterioration, damage and other deleterious processes. These effects hamper the capacity and efficiency of transportation networks and adversely impact local, regional and national economic growth. As a result, bridge authorities and other professionals have become more sensitive to maintenance issues related to this aging infrastructure. While highway bridge condition have been monitored by visual inspection, non-destructive evaluation (NDE) technologies have also been developing and they are expected to be utilized for effective management of highway bridges or other civil infrastructure systems. Efficient use of these technologies saves time spent or bridge inspections, and also helps the bridge authorities for management decision-making. One of the NDE technologies is the image-based technology. In this thesis research, image-based technologies using high resolution digital images (HRDI) and infrared thermography image (IRTI) are introduced, described and implemented.First, a review of the mechanisms of these technologies is presented. Due to the specific engineering utilization and recent technological development, there is a need to validate effectiveness of HRDI and IRTI for their practical use for engineering purpose. For this reason, a pilot project using these technologies was conducted at an in-service bridge and a parking structure with the support of Florida Department of Transportation District 5 and the results are presented in this thesis. Secondly, in order to explore and enhance the usability of infrared thermography technology (IRTI), experiments on campus and on another bridge were conducted to determine the best time to test bridges and the sensitivity of IRTI to delamination volume. Since the accuracy of damage detection using infrared thermography technology is greatly affected by daily temperature variation, it is quite important to estimate an appropriate duration for infrared thermography inspection prior to the inspection. However, in current practice, the way to estimate the duration is to monitor the temperature of the concrete surface. Since the temperature varies depending on the area or region, there is a need to visit the bridge before the actual test and monitor the temperature variation. This requires additional visits to the bridge site and also access to the bridge for measuring concrete temperature. Sometimes, this can be a practical issue. In this research, in order to estimate an appropriate duration without visiting bridges, a practical method is explored by monitoring and analyzing variation of concrete surface temperature at one location and projected to another location by also incorporating other factors that affect the concrete temperature, such as air temperature and humidity. For this analysis, specially-designed concrete plates of a few types of thickness and shapes are used and the regression analysis is employed to establish a relationship between environmental effects and temperature variation between two different sites. The results have been promising for this research study and it is shown that HRDI and IRTI are excellent technologies for assessing concrete structures in a very practical manner.
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Date Issued: 2013
Identifier: CFE0004956, ucf:49581
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004956

Title: PHASE SHAPING IN THE INFRARED BY PLANAR QUASI-PERIODIC SURFACES COMPRISED OF SUB-WAVELENGTH ELEMENTS.
Creator: Ginn, James, Boreman, Glenn, University of Central Florida
Abstract / Description: Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time – at frequencies as...
Show moreReflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time – at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized metallic patch resonator in terms of its dependence on element dimensions, surrounding materials, angle of incidence, and frequency. The impact of realistic dispersion of the real and imaginary parts of the metallic permittivity on the magnitude and bandwidth of the resonance behavior is thoroughly investigated. Several single-phase reflectarrays are fabricated and measurement techniques are developed for evaluating these surfaces. In all of these cases, there is excellent agreement between the computational model results and the measured device characteristics. With accurate modeling and measurement, it is possible to proceed to explore some specific device architectures appropriate for focusing reflectarrays, including binary-phase and phase-incremental approaches. Image quality aspects of these focusing reflectarrays are considered from geometrical and chromatic-aberration perspectives. The dissertation concludes by briefly considering two additional analogous devices – the transmitarray for tailoring transmissive phase response, and the emitarray for angular control of thermally emitted radiation.
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Date Issued: 2009
Identifier: CFE0002707, ucf:48186
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002707

Title: Synchrotron based infrared microspectroscopy of carbonaceous chondrites.
Creator: Yesiltas, Mehmet, Peale, Robert, Fernandez, Yan, Britt, Daniel, Reach, William, University of Central Florida
Abstract / Description: Relationships between organic molecules and inorganic minerals are investigated in five carbonaceous chondrites, Northwest Africa 852 (CR2), Tagish Lake (C2-ungroupped), Orgueil (CI1), Sutter's Mill (CM), and Murchison (CM2), with micron spatial resolution using synchrotron-based imaging micro-FTIR spectroscopy. Correlations based on absorption strength for various constituents are determined using statistical correlation analysis. Silicate band is found to be positively correlated with...
Show moreRelationships between organic molecules and inorganic minerals are investigated in five carbonaceous chondrites, Northwest Africa 852 (CR2), Tagish Lake (C2-ungroupped), Orgueil (CI1), Sutter's Mill (CM), and Murchison (CM2), with micron spatial resolution using synchrotron-based imaging micro-FTIR spectroscopy. Correlations based on absorption strength for various constituents are determined using statistical correlation analysis. Silicate band is found to be positively correlated with stretching modes of aliphatic hydrocarbons in NWA 852 and Tagish Lake. The former is highly correlated with the hydration band in all meteorites. Negative correlation is observed between water+organics and carbonate bands in all meteorites. Two dimensional infrared maps for NWA 852 and Orgueil show that carbonates are spatially separated from water+organic combination, silicates, OH, and CH distributions. Overlapping of the latter three in NWA 852 and Tagish Lake suggests a possible catalytic role of phyllosilicates in the formation of organics. Additionally, spectroscopic analyses on Sutter's Mill meteorite fragments present multiple distinct mineralogies. Spatial and spectral evidences on this regolith breccia suggest mixing of multiple parent bodies. Ratios of asymmetric CH2 and CH3 band strengths for NWA 852, Tagish Lake, and Sutter's Mill are similar to the average ratio of interplanetary dust particles and Wild 2 cometary dust particles, however significantly exceeds that of interstellar medium objects and several aqueously altered carbonaceous chondrites such as Orgueil. This suggests distinct formation regions and/or parent body processing of organics for these meteorites. Our infrared spectro-microtomography measurements on Murchison meteorite, representing the first such measurement on any kind of meteorite, comprise of three-dimensional reconstructions of specific molecular functional groups for understanding the spatial distributions of these groups.
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Date Issued: 2015
Identifier: CFE0006061, ucf:50966
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006061

Title: Studying Short-Period Comets and Long-Period Comets Detected by WISE/NEOWISE.
Creator: Kramer, Emily, Fernandez, Yan, Colwell, Joshua, Kokoouline, Viatcheslav, Klemm, Richard, Lisse, Carey, University of Central Florida
Abstract / Description: The Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22 ?m) between January 2010 and February 2011. During the mission, WISE serendipitously observed 160 comets, including 21 newly discovered objects. About 89 of the comets observed by WISE displayed a significant dust tail in the 12 and 22 ?m (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both...
Show moreThe Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22 ?m) between January 2010 and February 2011. During the mission, WISE serendipitously observed 160 comets, including 21 newly discovered objects. About 89 of the comets observed by WISE displayed a significant dust tail in the 12 and 22 ?m (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both long-period comets (LPCs) and short-period comets (SPCs), differences in their activity can be used to better understand the thermal evolution that each of these populations has undergone. For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method [Finson and Probstein, 1968]. For a selection of 40 comets, we have then compared these models to the data using a novel tail-fitting method that allows the best-fit model to be chosen analytically rather than subjectively. For comets that were observed multiple times by WISE, the particle properties were estimated separately, and then compared. We find that the dust tails of both LPCs and SPCs are primarily comprised of ?mm-cm sized particles, which were the result of emission that occurred several months to several years prior to the observations. The LPCs nearly all have strong emission close to the comet's perihelion distance, and the SPCs mostly have strong emission close to perihelion, but some have strong emission well before perihelion.
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Date Issued: 2014
Identifier: CFE0005823, ucf:50938
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005823

Title: Uncooled Infrared Detector Featuring Silicon based Nanoscale Thermocouple.
Creator: Modarres-Zadeh, Mohammad, Abdolvand, Reza, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Malocha, Donald, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: The main focus of this dissertation is to improve the performance of thermoelectric (TE)infrared (IR) detectors. TE IR detectors are part of uncooled detectors that can operate at roomtemperature. These detectors have been around for many years, however, their performance hasbeen lower than their contesting technologies. A novel high-responsivity uncooled thermoelectricinfrared detector is designed, fabricated, and characterized. This detector features a single standalonepolysilicon-based...
Show moreThe main focus of this dissertation is to improve the performance of thermoelectric (TE)infrared (IR) detectors. TE IR detectors are part of uncooled detectors that can operate at roomtemperature. These detectors have been around for many years, however, their performance hasbeen lower than their contesting technologies. A novel high-responsivity uncooled thermoelectricinfrared detector is designed, fabricated, and characterized. This detector features a single standalonepolysilicon-based thermocouple (without a supporting membrane) covered by an umbrellalikeoptical-cavity IR absorber. It is proved that the highest responsivity in the developed detectorscan be achieved with only one thermocouple. Since the sub-micrometer polysilicon TE wires arethe only heat path from the hot junction to the substrate, a superior thermal isolation is achieved.A responsivity of 1800 V/W and a detectivity of 2 ? 10^8 (cm. sqrt(Hz)W^?1) are measured from a20?m x 20?m detector comparable to the performance of detectors used in commercial focalplanar arrays. This performance in a compact and manufacturable design elevates the position ofthermoelectric IR sensors as a candidate for low-power, high performance, and inexpensive focalplanar arrays. The improvement in performance is mostly due to low thermal conductivity of thinpolysilicon wires. A feature is designed and fabricated to characterize the thermal conductivity ofsuch a wire and it is shown for the first time that the thermal conductivity of thin polysilicon filmscan be much lower than that of the bulk. Thermal conductivity of ~110nm LPCVD polysilicondeposited at 620C is measured to be ~3.5W/m.K.
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Date Issued: 2016
Identifier: CFE0006537, ucf:51321
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006537

Title: Low Absorption Liquid Crystal Materials for Midwave Infrared.
Creator: Creekmore, Amy, Wu, Shintson, Moharam, Jim, Likamwa, Patrick, University of Central Florida
Abstract / Description: Liquid crystal is an amazing class of soft matters with applications spanning from visible, infrared, millimeter wave, to terahertz. In addition to direct-view displays and projection displays, liquid crystal is also widely used in adaptive optics, tunable-focus lens, and laser beam steering. Although the visible region has well developed materials and mixtures for the vast variety of applications, the midwave infrared (MWIR) region of the electromagnetic spectrum invites much development as...
Show moreLiquid crystal is an amazing class of soft matters with applications spanning from visible, infrared, millimeter wave, to terahertz. In addition to direct-view displays and projection displays, liquid crystal is also widely used in adaptive optics, tunable-focus lens, and laser beam steering. Although the visible region has well developed materials and mixtures for the vast variety of applications, the midwave infrared (MWIR) region of the electromagnetic spectrum invites much development as only a few materials have been developed with these applications in mind. Unlike visible region, the major challenge for mid-wave infrared liquid crystal is inherently large absorption loss. To reduce absorption, some molecular engineering approaches have been considered, such as deuteration, fluorination, and chlorination. The fluorine and chlorine not only act as the polar group to provide dipole moment but also helps shift some vibration absorption bands outside the MWIR window. Long phenyl ring compounds, fluorinated tolane materials, and chlorinated terphenyl mixtures are explored; as well as a look as the potential bromine might introduce for future development. In this thesis, we first review the current materials and their performance in the mid-wave infrared region, explain the need for higher performing liquid crystals, and then discuss the methodology of compound development and mixture formulation. Some new chlorinated liquid crystal compounds are synthesized, mixture formulated, and their properties evaluated. Finally, we will explain the future work which needs to be performed in this field.
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Date Issued: 2014
Identifier: CFE0005594, ucf:50243
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005594

Title: Large Area Conformal Infrared Frequency Selective Surfaces.
Creator: Darchangel, Jeffrey, Schoenfeld, Winston, Boreman, Glenn, Likamwa, Patrick, Kik, Pieter, Lail, Brian, University of Central Florida
Abstract / Description: Frequency selective surfaces (FSS) were originally developed for electromagnetic filtering applications at microwave frequencies. Electron-beam lithography has enabled the extension of FSS to infrared frequencies; however, these techniques create sample sizes that are seldom appropriate for real world applications due to the size and rigidity of the substrate. A new method of fabricating large area conformal infrared FSS is introduced, which involves releasing miniature FSS arrays from a...
Show moreFrequency selective surfaces (FSS) were originally developed for electromagnetic filtering applications at microwave frequencies. Electron-beam lithography has enabled the extension of FSS to infrared frequencies; however, these techniques create sample sizes that are seldom appropriate for real world applications due to the size and rigidity of the substrate. A new method of fabricating large area conformal infrared FSS is introduced, which involves releasing miniature FSS arrays from a substrate for implementation in a coating. A selective etching process is proposed and executed to create FSS particles from crossed-dipole and square-loop FSS arrays. When the fill-factor of the particles in the measurement area is accounted for, the spectral properties of the FSS flakes are similar to the full array from which they were created. As a step toward scalability of the process, a square-patch design is presented and formed into FSS flakes with geometry within the capability of ultraviolet optical lithography.Square-loop infrared FSS designs are investigated both in quasi-infinite arrays and in truncated sub-arrays. First, scattering-scanning near-field optical microscopy (s-SNOM) is introduced as a characterization method for square-loop arrays, and the near-field amplitude and phase results are discussed in terms of the resonant behavior observed in far-field measurements. Since the creation of FSS particles toward a large area coating inherently truncates the arrays, array truncation effects are investigated for square-loop arrays both in the near- and far-field. As an extension of the truncation study, small geometric changes in the design of square-loop arrays are introduced as a method to tune the resonant far-field wavelength back to that of the quasi-infinite arrays.
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Date Issued: 2014
Identifier: CFE0005476, ucf:50348
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005476

Title: An uncooled mid-wave infrared detector based on optical response of laser-doped silicon carbide.
Creator: Lim, Geunsik, Kar, Aravinda, Coffey, Kevin, Vaidyanathan, Raj, Dhere, Neelkanth, Likamwa, Patrick, University of Central Florida
Abstract / Description: This dissertation focuses on an uncooled Mid-Wave Infra-Red (MWIR) detector was developed by doping an n-type 4H-SiC with Ga using the laser doping technique. 4H-SiC is one of the polytypes of crystalline silicon carbide, a wide bandgap semiconductor. The dopant creates an energy level of 0.30 eV, which was confirmed by optical spectroscopy of the doped sample. This energy level corresponds to the MWIR wavelength of 4.21 um. The detection mechanism is based on the photoexcitation of electrons...
Show moreThis dissertation focuses on an uncooled Mid-Wave Infra-Red (MWIR) detector was developed by doping an n-type 4H-SiC with Ga using the laser doping technique. 4H-SiC is one of the polytypes of crystalline silicon carbide, a wide bandgap semiconductor. The dopant creates an energy level of 0.30 eV, which was confirmed by optical spectroscopy of the doped sample. This energy level corresponds to the MWIR wavelength of 4.21 um. The detection mechanism is based on the photoexcitation of electrons by the photons of this wavelength absorbed in the semiconductor. This process modifies the electron density, which changes the refraction index and, therefore, the reflectance of the semiconductor is also changed. The change in the reflectance, which is the optical response of the detector, can be measured remotely with a laser beam such as a He-Ne laser. This capability of measuring the detector response remotely makes it a wireless optical detector. The variation of refraction index was calculated as a function of absorbed irradiance based on the reflectance data for the as-received and doped samples. A distinct change was observed for the refraction index of the doped sample, indicating that the detector is suitable for applications at 4.21 um wavelength. The Ga dopant energy level in the substrate was confirmed by optical absorption spectroscopy. Secondary ion mass spectroscopy (SIMS) of the doped samples revealed an enhancement in the solid solubility of Ga in the substrate when doping is carried out by increasing the number of laser scans. Higher dopant concentration increases the number of holes in the dopant energy level, enabling photoexcitation of more electrons from the valence band by the incident MWIR photons. The detector performance improves as the dopant concentration increases from 1.15(&)#215;1019 to 6.25(&)#215;10^20 cm^-3. The detectivity of the optical photodetector is found to be 1.07(&)#215;10^10 cm?Hz^1/2/W for the case of doping with 4 laser passes. The noise mechanisms in the probe laser, silicon carbide MWIR detector and laser power meter affect the performance of the detector such as the responsivity, noise equivalent temperature difference (NETD) and detectivity. For the MWIR wavelength 4.21 and 4.63 um, the experimental detectivity of the optical photodetector of this study is found to be 1.07(&)#215;10^10 cm?Hz^1/2/W, while the theoretical value is 2.39(&)#215;10^10 cm?Hz^1/2/W. The values of NETD are found to be 404.03 and 15.48 mK based on experimental data for an MWIR radiation source of temperature 25(&)deg;C and theoretical calculation respectively.The doped SiC also has a capability of gas detection since gas emission spectra are in infrared range. Similarly, the sensor is based on the semiconductor optics principle, i.e., an energy gap is created in a semiconductor by doping it with an appropriate dopant to ensure that the energy gap matches with an emission spectral line of the gas of interest. Specifically four sensors have been fabricated by laser doping four quadrants of a 6H-SiC substrate with Ga, Al, Sc and P atoms to detect CO2, NO, CO and NO2 gases respectively. The photons, which are emitted by the gas, excite the electrons in the doped sample and consequently change the electron density in various energy states. This phenomenon affects the refraction index of the semiconductor and, therefore, the reflectivity of the semiconductor is altered by the gas. The optical response of this semiconductor sensor is the reflected power of a probe beam, which is a He-Ne laser beam in this study. The CO2, NO, CO and NO2 gases change the refraction indices of Ga-, Al-, Sc- and Al-doped 6H-SiC, respectively, more prominently than the other gases tested in this study. Hence these doped 6H-SiC samples can be used as CO2, NO, CO and NO2 gas sensors respectively.
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Date Issued: 2014
Identifier: CFE0005519, ucf:50310
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005519

Title: Multimaterial fibers in photonics and nanotechnology.
Creator: Tao, Guangming, Abouraddy, Ayman, Li, Guifang, Glebov, Leonid, Peale, Robert, University of Central Florida
Abstract / Description: Recent progress in combing multiple materials with distinct optical, electronic, and thermomechanical properties monolithically in a kilometer-long fiber drawn from a preform offers unique multifunctionality at a low cost. A wide range of unique in-fiber devices have been developed in fiber form-factor using this strategy. Here, I summary my recent results in this nascent field of 'multimaterial fibers'. I will focus on my achievements in producing robust infrared optical fibers and in...
Show moreRecent progress in combing multiple materials with distinct optical, electronic, and thermomechanical properties monolithically in a kilometer-long fiber drawn from a preform offers unique multifunctionality at a low cost. A wide range of unique in-fiber devices have been developed in fiber form-factor using this strategy. Here, I summary my recent results in this nascent field of 'multimaterial fibers'. I will focus on my achievements in producing robust infrared optical fibers and in appropriating optical fiber production technology for applications in nanofabrication.The development of optical components suitable for the infrared (IR) is crucial for applications in this spectral range to reach the maturity level of their counterparts in the visible and near-infrared spectral regimes. A critical class of optical components that has yet to be fully developed is that of IR optical fibers. Here I will present several unique approaches that may result in low-cost, robust IR fibers that transmit light from 1.5 microns to 15 microns drawn from multimaterial preforms. These preforms are prepared exploiting the newly developed procedure of multimaterial coextrusion, which provides unprecedented flexibility in material choices and structure engineering in the extruded preform. I will present several different 'generations' of multimaterial extrusion that enable access to a variety of IR fibers. Examples of the IR fibers realized using this methodology include single mode IR fibers, large index-contrast IR fibers, IR imaging fiber bundles, IR photonic crystal and potentially photonic band-gap fibers.The complex structures produced in multimaterial fibers may also be used in the fabrication of micro- and nano-scale spherical particles by exploiting a recently discovered in-fiber Plateau-Rayleigh capillary instability. Such multimaterial structured particles have promising application in drug delivery, optical sensors, and nanobiotechnology. The benefits accrued from the multimaterial fiber methodology allow for the scalable fabrication of micro- and nano-scale particles having complex internal architectures, such as multi-shell particles, Janus-particles, and particles with combined control over the radial and azimuthal structure.Finally, I will summarize my views on the compatibility of a wide range of amorphous and crystalline materials with the traditional thermal fiber drawing process and with the more recent multimaterial fiber strategy.
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Date Issued: 2014
Identifier: CFE0005555, ucf:50289
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005555

Title: ANTENNA-COUPLED INFRARED AND MILLIMETER-WAVE DETECTORS: FABRICATION, MEASUREMENT AND OPTIMIZATION.
Creator: Middleton, Charles, Boreman, Glenn, University of Central Florida
Abstract / Description: 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...
Show moreAntenna-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.
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Date Issued: 2006
Identifier: CFE0001242, ucf:46908
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001242

Title: Broadband Mid-infrared Frequency Combs Generated via Frequency Division.
Creator: Ru, Qitian, Vodopyanov, Konstantin, Fathpour, Sasan, Wu, Shintson, Peale, Robert, University of Central Florida
Abstract / Description: Frequency combs have revolutionized metrology and demonstrated numerous applications in science and technology. Combs operating in the mid-infrared region could be beneficial for molecular spectroscopy for several reasons. First, numerous molecules have their spectroscopic signatures in this region. Furthermore, the atmospheric window (3-5(&)#181;m and 8-14(&)#181;m) is located here. Additionally, a mid-infrared frequency comb could be employed as a diagnostic tool for the many components of...
Show moreFrequency combs have revolutionized metrology and demonstrated numerous applications in science and technology. Combs operating in the mid-infrared region could be beneficial for molecular spectroscopy for several reasons. First, numerous molecules have their spectroscopic signatures in this region. Furthermore, the atmospheric window (3-5(&)#181;m and 8-14(&)#181;m) is located here. Additionally, a mid-infrared frequency comb could be employed as a diagnostic tool for the many components of human breath, as well as for detection of harmful gases and contaminants in the atmosphere. In this thesis, I used synchronously pumped subharmonic optical parametric oscillators (OPOs) operating at degeneracy to produce ultra-broadband outputs near half of the pump laser frequency. One attractive property of the subharmonic OPOs is that the signal/idler waves of the OPO are frequency- and phase-locked to the pump frequency comb. We explored three new nonlinear materials in the subharmonic OPO and demonstrated a broadband spectrum for mid-infrared frequency comb generation. (1) Orientation-patterned (OP) gallium arsenide (GaAs) was selected as the first material because it has high nonlinearity. We found that the OP-GaAs based OPO yielded an approximately two-octave wide spectrum (2.8(-)11(&)#181;m). (2) Gallium phosphide (GaP) has near zero group velocity dispersion (GVD) at 4.7 (&)#181;m and a large bandgap. The OP-GaP OPO yielded a spectrum of more than two octaves (3(-)12.5(&)#181;m). Also, because of the large bandgap, GaP is suitable for telecom 1.56-(&)#181;m pumping, having the advantage of much smaller GVD than in periodically-poled-lithium-niobite (PPLN). The telecom laser (1.56(&)#181;m) pumped OP-GaP OPO was demonstrated with more than one octave wide spectrum. (3) Finally, we explored the phenomenon of random phase matching in the zinc selenide (ZnSe) polycrystalline material. The first random phase matched OPO was demonstrated with more than one octave spectrum (3.1(-) 9(&)#181;m), which is also the first OPO based on ZnSe.
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Date Issued: 2019
Identifier: CFE0007718, ucf:52430
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007718

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