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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: 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: ANTENNA-COUPLED TUNNEL DIODES FOR DUAL-BAND MILLIMETER-WAVE/INFRARED FOCAL-PLANE ARRAYS.
Creator: Abdel Rahman, Mohamed, Boreman, Glenn, University of Central Florida
Abstract / Description: 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...
Show moreThe 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.
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Date Issued: 2004
Identifier: CFE0000305, ucf:46309
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000305

Title: FAR-INFRARED/MILLIMETER WAVE SOURCE AND COMPONENT DEVELOPMENT FOR IMAGING AND SPECTROSCOPY.
Creator: Du Bosq, Todd, Boreman, Glenn, University of Central Florida
Abstract / Description: 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...
Show moreThe 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.
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Date Issued: 2007
Identifier: CFE0001665, ucf:47222
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001665

Title: DESIGN AND DEMONSTRATION OF MEANDERLINE RETARDERS AT INFRARED FREQUENCIES.
Creator: Tharp, Jeffrey, Boreman, Glenn, University of Central Florida
Abstract / Description: Meanderline structures are widely used as engineered birefringent materials for waveplates and retarders at radiofrequencies, and have been previously demonstrated at frequencies up to 90 GHz in the millimeter-wave band. In this dissertation, we present results related to the modeling, fabrication, and experimental characterization of meanderlines across the range from 30 to 100 THz, in the long-wave and mid-wave infrared bands. Specific issues addressed in these new designs include spectral...
Show moreMeanderline structures are widely used as engineered birefringent materials for waveplates and retarders at radiofrequencies, and have been previously demonstrated at frequencies up to 90 GHz in the millimeter-wave band. In this dissertation, we present results related to the modeling, fabrication, and experimental characterization of meanderlines across the range from 30 to 100 THz, in the long-wave and mid-wave infrared bands. Specific issues addressed in these new designs include spectral dispersion and angular dependence of the retardance, as well as axial ratio and throughput. The impact resulting from the infrared properties of the metals and dielectrics is explicitly included throughout. Several novel applications are identified, including integrated circular polarizers, reflective waveplates, and large-area polarization tags.
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Date Issued: 2007
Identifier: CFE0001884, ucf:47396
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001884

Title: INFRARED ANTENNA-COUPLED PHASED-ARRAY.
Creator: Middlebrook, Christopher, Boreman, Glenn, University of Central Florida
Abstract / Description: Phased-array antennas are commonplace in the radiofrequency portion of the electromagnetic spectrum. Exploitation of phasing effects between multiple antennas facilitates a wide range of applications, including synthetic-aperture radar, beam forming, and beam scanning. For the first time, the phased addition of multiple dipole antennas is demonstrated in the infrared, at a wavelength of 10.6 micrometers. Coplanar strip lines are used to interconnect the antennas, preserving the phase of the...
Show morePhased-array antennas are commonplace in the radiofrequency portion of the electromagnetic spectrum. Exploitation of phasing effects between multiple antennas facilitates a wide range of applications, including synthetic-aperture radar, beam forming, and beam scanning. For the first time, the phased addition of multiple dipole antennas is demonstrated in the infrared, at a wavelength of 10.6 micrometers. Coplanar strip lines are used to interconnect the antennas, preserving the phase of the individual contributions. Several different proof-of-concept experiments are performed, using planar antennas fabricated with direct-write electron-beam lithography. Infrared-frequency currents from two dipole antennas are summed together at a common feedpoint and dissipated in a bolometric load. Angular pattern measurements show that the direction of maximum gain depends on the phase difference between the antennas. As more antennas are added together in phase, beam narrowing is observed in the angular response. Another experiment uses a two-dipole array to directly measure the magnitude of the mutual coherence function, at the plane of the antennas, of a spatially incoherent narrowband source. Measurements are also made of the broadside antenna response comparing air-side and substrate-side situations for a dipole antenna fabricated on a hemispherical immersion lens. In all cases, the measured behavior is confirmed by electromagnetic analysis.
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Date Issued: 2007
Identifier: CFE0001709, ucf:47327
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001709

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: RESPONSE-CALIBRATION TECHNIQUES FOR ANTENNA-COUPLED INFRARED SENSORS.
Creator: Krenz, Peter, Boreman, Glenn, University of Central Florida
Abstract / Description: Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the...
Show moreInfrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous signal contributions can be measured separately with calibration structures closely co-located near the devices to be characterized. This approach is demonstrated in two specific embodiments, for removal of cross-polarization effects arising from lead lines in an antenna-coupled infrared dipole, and for removal of distributed thermal effects in an infrared phased-array antenna. The second calibration technique uses scanning near-field microscopy to experimentally determine the spatial dependence of the electric-field distributions on the signal-extraction structures, and to include these measured fields in the computational electromagnetic model of the overall device. This approach is demonstrated for infrared dipole antennas which are connected to coplanar strip lines. Specific situations with open-circuit and short-circuit impedances at the termination of the lines are investigated.
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Date Issued: 2010
Identifier: CFE0003177, ucf:48606
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003177

Title: MULTILAYERED PLANAR PERIODIC SUBWAVELENGTH MICROSTRUCTURES FOR GENERATING AND DETECTING CIRCULARLY POLARIZED THERMAL INFRARED RADIATION.
Creator: Wadsworth, Samuel, Boreman, Glenn, University of Central Florida
Abstract / Description: Generation and detection of circularly-polarized (CP) radiation in the 8- to 12-[micro]m band of the infrared (IR) spectrum is crucial for polarization sensing and imaging scenarios. There is very little naturally occurring CP radiation in the long-wave IR band, so that useful functionalities may be obtained by exploiting preferential radiation and transmission characteristics of engineered metamaterials. Conventional CP devices in the IR utilize birefringent crystals, which are typically...
Show moreGeneration and detection of circularly-polarized (CP) radiation in the 8- to 12-[micro]m band of the infrared (IR) spectrum is crucial for polarization sensing and imaging scenarios. There is very little naturally occurring CP radiation in the long-wave IR band, so that useful functionalities may be obtained by exploiting preferential radiation and transmission characteristics of engineered metamaterials. Conventional CP devices in the IR utilize birefringent crystals, which are typically bulky and expensive to manufacture. The operation of these devices is generally optimized at a single wavelength. Imaging in the long-wave IR is most often broadband, so that achromatic CP-device behavior is highly desirable from a flux-transfer viewpoint. Also, size, weight and cost are significant drivers in the design of practical IR systems. Thus a solution is sought with a convenient thin planar form factor. This dissertation will demonstrate a novel planar periodic subwavelength-microstructured approach derived from classical radiofrequency meanderline designs that are able to generate CP radiation over a broad IR band while maintaining a low fabrication profile. We investigate issues regarding efficiency as a function of the number of layers in the device structure; reflective, transmissive, and emissive behavior; strategies for broadband achromatization; and thermal-isolation requirements between the active blackbody reservoir and the top of the planar device, to achieve a given degree of polarization. Theoretical, numerical, and experimental findings are presented that confirm the feasibility of this class of devices for use in a wide variety of situations, from polarization imaging and spectroscopy to industrial laser processing and machining.
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Date Issued: 2011
Identifier: CFE0003935, ucf:48686
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003935

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: 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: APPLICATION OF ANTENNA SYNTHESIS AND DIGITAL SIGNAL PROCESSING TECHNIQUES FOR ACTIVE MILLIMETER-WAVE IMAGING SYSTEMS.
Creator: Caba, Wilson, Boreman, Glenn, University of Central Florida
Abstract / Description: Millimeter-wave imaging has gathered attention in recent years for its ability to penetrate clothing, thin layers of soils, and certain construction materials. However, image quality remains a challenge that needs to be addressed. One way of improving image quality is by increasing the dimensions of the collecting aperture. A sparse array can be used to synthesize a larger aperture with a limited set of relatively small detectors. In this research we design, build, and test a test-bed having...
Show moreMillimeter-wave imaging has gathered attention in recent years for its ability to penetrate clothing, thin layers of soils, and certain construction materials. However, image quality remains a challenge that needs to be addressed. One way of improving image quality is by increasing the dimensions of the collecting aperture. A sparse array can be used to synthesize a larger aperture with a limited set of relatively small detectors. In this research we design, build, and test a test-bed having an active source at 94 GHz and an array of coherent detectors, mounted on arms that extend radially on a rotary table. Using this test bed a circular area with a maximum diameter of 900 mm can be scanned. The signal is down-converted using heterodyne receivers with digital in-phase and quadrature detection. Signal correlation is performed using the digitized data, which is stored for post-processing, electronic focusing, and image reconstruction. Near-field imaging using interferometric reconstructions is achieved using electronic focusing. Imaging tests show the ability of the system to generate imagery of concealed and unconcealed objects at distances between 400 and 700 mm. A study of the effects of redundant and non-redundant configurations on image quality for 4 common detector configurations is presented. In this document we show that an active sparse-aperture imaging system using digital correlators is a viable way to generate millimeter-wave images.
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Date Issued: 2010
Identifier: CFE0003406, ucf:48429
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003406

Title: TUNABLE INFRARED METAMATERIALS.
Creator: Shelton, David, Boreman, Glenn, University of Central Florida
Abstract / Description: Metamaterials are engineered periodic composites that have unique refractive-index characteristics not available in natural materials. They have been demonstrated over a large portion of the electromagnetic spectrum, from visible to radiofrequency. For applications in the infrared, the structure of metamaterials is generally defined using electron-beam lithography. At these frequencies, the loss and dispersion of any metal included in the composite are of particular significance. In this...
Show moreMetamaterials are engineered periodic composites that have unique refractive-index characteristics not available in natural materials. They have been demonstrated over a large portion of the electromagnetic spectrum, from visible to radiofrequency. For applications in the infrared, the structure of metamaterials is generally defined using electron-beam lithography. At these frequencies, the loss and dispersion of any metal included in the composite are of particular significance. In this regard, we investigate deviations from the Drude model due to the anomalous skin effect. For comparison with theoretical predictions, the optical properties of several different metals are measured, both at room temperature and at 4 K. We extend this analysis to the coupling between plasmon and phonon modes in a metamaterial, demonstrating that very thin oxide layers residing at the metal-substrate interface will significantly affect the spectral location of the overall resonance. Oxide-thickness-dependent trends are then explored in some detail. Potential applications of this general area of study include surface-enhanced infrared spectroscopy for chemical sensing, and development of narrowband notch filters in the very long wavelength infrared. We then consider various possibilities for development of tunable infrared metamaterials. These would have wide applicability in dynamically variable reflectance surfaces and in beam steering. We consider several methods that have been previously shown to produce tunable metamaterials in the radio frequency band, and explore the challenges that occur when such techniques are attempted at infrared frequencies. A significant advance in tunable-infrared-metamaterial technology is then demonstrated with the use of thermochromic vanadium dioxide thin films. Highlights include the first demonstration of a tunable reflectarray in the infrared for active modulation of reflected phase, the first demonstration of a tunable resonance frequency in the thermal infrared band, and the largest resonance-frequency shift recorded to date in any part of the infrared. Finally, future work is proposed that holds the promise of wideband frequency tuning and electronically-controllable metamaterials.
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Date Issued: 2010
Identifier: CFE0003201, ucf:48575
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003201

Title: Antenna-coupled infrared focal plane array.
Creator: Gonzalez, Francisco Javier, Boreman, Glenn D., Engineering and Computer Sciences
Abstract / Description: University of Central Florida College of Engineering Thesis; In this dissertation a new type of infared focal plan array (IR FPA) was investigated, consisting of antenna-coupled microbolometer fabricated using electron-beam lithography. Four different antenna designs were experimentally demonstrated at 10-micron wavelength: dipole, bowtie, square-spiral, and log-periodic. The main differences between these antenna types were their bandwidth, collection area, angular reception pattern, and...
Show moreUniversity of Central Florida College of Engineering Thesis; In this dissertation a new type of infared focal plan array (IR FPA) was investigated, consisting of antenna-coupled microbolometer fabricated using electron-beam lithography. Four different antenna designs were experimentally demonstrated at 10-micron wavelength: dipole, bowtie, square-spiral, and log-periodic. The main differences between these antenna types were their bandwidth, collection area, angular reception pattern, and polarization. To provide pixel collection areas commensurate with typical IR FPA requirements, two configuration were investigated: a two-dimensional serpentine interconnection of individual IR antennas, and a Fresnel-zone-plate (FZP) coupled to a single-element antenna. Optimum spacing conditions for the two-dimensional interconnect were developed. Increased sensitivity was demonstrated using a FZP-coupled design. In general, it was found that the configuration of the antenna substrate material was critical for optimization of sensitivity. The best results were obtained using this membranes of silicon nitride to enhance the thermal isolation of the antenna-coupled bolometers. In addition, choice of the bolometer material was also important, with the best results obtained using vanadium oxide. Using optimum choices for all parameters, normalized sensitivity (D*) values in the range of mid 10^8 [cmâˆšHz/W] were demonstrated for antenna-coupled IR sensors, and directions for further improvements were identified. Successful integration of antenna-coupled pixels with commercial readout integrated circuits was also demonstrated.
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Date Issued: 2003
Identifier: CFR0011595, ucf:53049
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFR0011595

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: Vanadium Oxide Microbolometers with Patterned Gold Black or Plasmonic Resonant Absorbers.
Creator: Smith, Evan, Peale, Robert, Khondaker, Saiful, Dove, Adrienne, Boreman, Glenn, University of Central Florida
Abstract / Description: High sensitivity uncooled microbolometers are necessary to meet the needs of the next generation of infrared detectors, which seek low power consumption and production cost without sacrificing performance. Presented here is the design, fabrication, and characterization of a microbolometer with responsivity enhanced by novel highly absorptive coatings. The device utilizes a gold-doped vanadium oxide film in a standard air bridge design. Performance estimations are calculated from current...
Show moreHigh sensitivity uncooled microbolometers are necessary to meet the needs of the next generation of infrared detectors, which seek low power consumption and production cost without sacrificing performance. Presented here is the design, fabrication, and characterization of a microbolometer with responsivity enhanced by novel highly absorptive coatings. The device utilizes a gold-doped vanadium oxide film in a standard air bridge design. Performance estimations are calculated from current theory, and efforts to maximize signal to noise ratio are shown and evaluated. Most notably, presented are the experimental results and analysis from the integration of two different absorptive coatings: a patterned gold black film and a plasmonic resonant structure.Infrared-absorbing gold black was selectively patterned onto the active surfaces of the detector. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves gold black's near unity absorptance. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. Infrared responsivity is improved 70% for mid-wave IR and 22% for long-wave IR. The increase in the thermal time constant caused by the additional mass of gold black is a modest 15%. However, this film is sensitive to thermal processing; experimental results indicate a decrease in absorptance upon device heating.Sub-wavelength resonant structures designed for long-wave infrared (LWIR) absorption have also been investigated. Dispersion of the dielectric refractive index provides for multiple overlapping resonances that span the 8-12 ?m LWIR wavelength band, a broader range than can be achieved using the usual resonance quarter-wave cavity engineered into the air-bridge structures. Experimental measurements show an increase in responsivity of 96% for mid-wave IR and 48% for long-wave IR, while thermal response time only increases by 16% due to the increased heat capacity. The resonant structures are not as susceptible to thermal processing as are the gold black films. This work suggests that plasmonic resonant structures can be an ideal method to improve detector performance for microbolometers.
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Date Issued: 2015
Identifier: CFE0006004, ucf:51026
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006004

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

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Boreman, Glenn (16)	+ -
University of Central Florida (16)	+ -
Lail, Brian (2)	+ -
Likamwa, Patrick (2)	+ -
Schoenfeld, Winston (2)	+ -

Abdel Rahman, Mohamed (1)	+ -
Boreman, Glenn D. (1)	+ -
Caba, Wilson (1)	+ -
Darchangel, Jeffrey (1)	+ -
Dove, Adrienne (1)	+ -
Du Bosq, Todd (1)	+ -
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Florence, Louis (1)	+ -
Ginn, James (1)	+ -
Gonzalez, Francisco Javier (1)	+ -
Khondaker, Saiful (1)	+ -
Kik, Pieter (1)	+ -
Krenz, Peter (1)	+ -
Mandviwala, Tasneem (1)	+ -
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Middleton, Charles (1)	+ -
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