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Author González, Francisco Javier; Alda, Javier; Ilic, Bojan; Boreman, Glenn D.
Title Infrared Antennas Coupled to Lithographic Fresnel Zone Plate Lenses Type Journal Article
Year (up) 2004 Publication Applied Optics Abbreviated Journal Appl. Opt.
Volume 43 Issue 33 Pages 6067-6073
Keywords optical antennas
Abstract Several designs for Fresnel zone plate lenses (FZPLs) to be used in conjunction with antenna-coupled infrared detectors have been fabricated and tested. The designs comprise square and circular FZPLs with different numbers of Fresnel zones working in transmissive or reflective modes designed to focus infrared energy on a square-spiral antenna connected to a microbolometer. A 163× maximum increase in response was obtained from a 15-zone circular FZPL in the transmissive mode. Sensor measurements of normalized detectivity D* resulted in a 2.67× increase with FZPLs compared with measurements made of square-spiral antennas without FZPLs. The experimental results are discussed and compared with values obtained from theoretical calculations.
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Call Number RPLAB @ gujma @ Serial 740
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Author Kramer, B.; Chen, C-C.; Volakis, J.D.
Title The development of a mini-UWB antenna Type Journal Article
Year (up) 2004 Publication Measurement and Techniques Association Symposium Abbreviated Journal AMTA
Volume Issue Pages 6
Keywords optical antennas; Ultra Wide Band; Spiral Antenna, Dielectric Loading
Abstract There is a great interest in the automotive and military sectors for small and broadband antennas that meet modern communication needs. These needs require ultra-wide bandwidth (>10:1) UWB antennas, such as the spiral antenna. However, the physical size at the low-frequency end typically becomes too large for practical applications. To reduce the size of the antenna, miniaturization techniques must be employed such as the use of high-contrast dielectric materials. Size reduction using high-contrast materials has been demonstrated for narrowband antennas, such as patch antennas, but not for broadband antennas to our knowledge. Therefore, the concept of miniaturizing a broadband spiral antenna using dielectric materials will be investigated experimentally and numerically.Issues that arise from dielectric loading such as impedance reduction will also be addressed. It will be shown using the results from these studies that there are practical limitations to the amount of miniaturization which can be achieved.
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Call Number RPLAB @ gujma @ Serial 751
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Author Alda, Javier; Rico-García, José M.; López-Alonso, José M.; Boreman, G.
Title Optical antennas for nano-photonic applications Type Journal Article
Year (up) 2005 Publication Nanotechnology Abbreviated Journal Nanotech.
Volume 16 Issue 5 Pages S230-S234
Keywords optical antennas
Abstract Antenna-coupled optical detectors, also named optical antennas, are being developed and proposed as alternative detection devices for the millimetre, infrared, and visible spectra. Optical and infrared antennas represent a class of optical components that couple electromagnetic radiation in the visible and infrared wavelengths in the same way as radioelectric antennas do at the corresponding wavelengths. The size of optical antennas is in the range of the detected wavelength and they involve fabrication techniques with nanoscale spatial resolution. Optical antennas have already proved and potential advantages in the detection of light showing polarization dependence, tuneability, and rapid time response. They also can be considered as point detectors and directionally sensitive elements. So far, these detectors have been thoroughly tested in the mid-infrared with some positive results in the visible. The measurement and characterization of optical antennas requires the use of an experimental set-up with nanometric resolution. On the other hand, a computation simulation of the interaction between the material structures and the incoming electromagnetic radiation is needed to explore alternative designs of practical devices.
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Call Number RPLAB @ gujma @ Serial 734
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Author González, F. J.; Boreman, G. D.
Title Comparison of dipole, bowtie, spiral and log-periodic IR antennas Type Journal Article
Year (up) 2005 Publication Infrared Physics & Technology Abbreviated Journal Inf Phys & Technol
Volume 46 Issue 5 Pages 418-428
Keywords optical antennas; Microbolometer; Infrared antennas; Antenna efficiency; Antenna-coupled detectors
Abstract Antenna-coupled microbolometers use planar lithographic antennas to couple infrared radiation into a bolometer with sub-micron dimensions. In this paper four different types of infrared antennas were fabricated on thin grounded-substrates and coupled to microbolometers. Dipole, bowtie, spiral and log-periodic IR antenna-coupled detectors were measured at 10.6 μm and their performance compared. A new method to calculate the radiation efficiency based on the spatial and angular response of infrared antennas is presented and used to evaluate their performance. The calculated radiation efficiency for the dipole, bowtie, spiral and log-periodic IR antennas was 20%, 37%, 25% and 46% respectively. A dipole-length study was performed and shows that the quasistatic value of the effective permittivity accurately describes the incident wavelength in the substrate at infrared frequencies for antennas on a thin substrate.
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Call Number RPLAB @ gujma @ Serial 739
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Author Gonzalez, F.J.; Ilic, B.; Alda, J.; Boreman, G.D.
Title Antenna-coupled infrared detectors for imaging applications Type Journal Article
Year (up) 2005 Publication IEEE J. Sel. Topics Quantum Electron. Abbreviated Journal
Volume 11 Issue 1 Pages 117 - 120
Keywords optical antennas
Abstract Infrared focal plane arrays (IRFPAs) are a critical component in advanced infrared imaging systems. IRFPAs are made up of two parts, a detector array and a readout integrated circuit (ROIC) multiplexer. Current ROIC technology has typical pitch sizes of 20×20 to 50×50 μm2. In order to make antenna-coupled detectors suited for infrared imaging systems, two-dimensional (2-D) arrays have been fabricated that cover a whole pixel area with the penalty of increasing the noise figure of the detector and, therefore, reducing its performance. By coupling a Fresnel zone plate lens to a single element antenna-coupled detector, infrared radiation can be collected over a typical pixel area and still keep low-noise levels. A Fresnel zone plate lens coupled to a single-element square-spiral-coupled infrared detector has been fabricated and its performance compared to single element antenna-coupled detectors and 2-D arrays of antenna coupled detectors. Measurements made at 10.6 μm showed a two-order-of-magnitude increase in SNR and a ~× increase in D* as compared to 2-D arrays of antenna-coupled detectors.
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Call Number RPLAB @ gujma @ Serial 741
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