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Saynak, UÄŸur |
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Novel rectangular spiral antennas |
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2008 |
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optical antennas |
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Round spiral antennas are generally designed by using Archimedean spiral geometries which have linear growth rates. To obtain smaller antennas with nearly the same performance, square spiral Archimedean geometries are also widely used instead. In this study, novel square antennas are proposed, designed and examined. At first two similar but different approaches are employed to design new antennas by considering the design procedure used to obtain log-periodic antennas. Then, the performance of these antennas is improved by considering another property of log-periodic antennas. Simulations are performed by using two different numerical methods which are Finite Difference Time Domain Method (FDTD) and Method of Moments (MoM). The results obtained from the simulations are compared with those of the Archimedean spiral antennas in terms of the frequency dependency of fundamental antenna parameters such as antenna gain and radiation pattern. The simulation results are compared with the ones obtained from the experimental study. |
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RPLAB @ gujma @ |
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750 |
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Tang, Liang; Kocabas, Sukru Ekin; Latif, Salman; Okyay, Ali K.; Ly-Gagnon, Dany-Sebastien; Saraswat, Krishna C.; Miller, David A. B. |
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Nanometre-scale germanium photodetector enhanced by a near-infrared dipole antenna |
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2008 |
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Nature Photonics |
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2 |
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226-229 |
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optical antennas |
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A critical challenge for the convergence of optics and electronics is that the micrometre scale of optics is significantly larger than the nanometre scale of modern electronic devices. In the conversion from photons to electrons by photodetectors, this size incompatibility often leads to substantial penalties in power dissipation, area, latency and noise. A photodetector can be made smaller by using a subwavelength active region; however, this can result in very low responsivity because of the diffraction limit of the light. Here we exploit the idea of a half-wave Hertz dipole antenna (length approx 380 nm) from radio waves, but at near-infrared wavelengths (length approx 1.3 microm), to concentrate radiation into a nanometre-scale germanium photodetector. This gives a polarization contrast of a factor of 20 in the resulting photocurrent in the subwavelength germanium element, which has an active volume of 0.00072 microm3, a size that is two orders of magnitude smaller than previously demonstrated detectors at such wavelengths. |
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858 |
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Novotny, Lukas |
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Title |
Effective wavelength scaling for optical antennas |
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2007 |
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Phys. Rev. Lett. |
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Phys. Rev. Lett. |
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98 |
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26 |
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266802(1-4) |
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optical antennas |
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In antenna theory, antenna parameters are directly related to the wavelength λ of incident radiation, but this scaling fails at optical frequencies where metals behave as strongly coupled plasmas. In this Letter we show that antenna designs can be transferred to the optical frequency regime by replacing λ by a linearly scaled effective wavelength λeff=n1+n2λ/λp, with λp being the plasma wavelength and n1, n2 being coefficients that depend on geometry and material properties. It is assumed that the antenna is made of linear segments with radii Râ‰<aa>λ. Optical antennas hold great promise for increasing the efficiency of photovoltaics, light-emitting devices, and optical sensors. |
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RPLAB @ gujma @ |
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749 |
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Novotny, L. |
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Title |
The history of near-field optics |
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2007 |
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Progress in Optics |
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Prog. Opt. |
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50 |
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137-180 |
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optical antennas |
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This article provides a review of early work and developments in the field of near-field optics. The roots trace back to the letters exchanged between Edward Hutchinson Synge and Albert Einstein in 1928 and, because of the analogy to antenna theory and lightning rods, the origins project back to the time of Benjamin Franklin who discovered the wonderful Effect of Points both in drawing off and throwing off the Electrical Fire. The modern interest was mainly inspired by the invention of scanning probe microscopy and by the first optical near-field measurements by Dieter W. Pohl and co-workers at the IBM Research Laboratory in R¨uschlikon, Switzerland, and also by parallel developments of other groups. Near-field optics received inspiration from the fields of surface enhanced spectroscopy and from studies of energy transfer. While optical near-fields were extensively exploited for overcoming the diffraction limit in optical imaging the study of their physical aspects revealed unique properties which cannot be imitated by free propagating radiation. |
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RPLAB @ gujma @ |
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752 |
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Brown, E. R.; Lee, A. W. M.; Navi, B. S.; Bjarnason, J. E. |
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Characterization of a planar self-complementary square-spiral antenna in the THz region |
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2006 |
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Microwave and Optical Technology Letters |
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Microwave Opt Technol Lett |
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48 |
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3 |
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524-529 |
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optical antennas; square spiral antenna; self complementary THz; photomixing; lens; method of moments; geometric optics; physical optics |
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This paper describes a compact, self-complementary square-spiral antenna on a GaAs substrate with a broadside high-directivity (~9 dB) frequency-independent pattern when coupled through a silicon hyperhemisphere. The driving-point resistance undulates between ~00 and 300Ω from 200 GHz to 1 THz—much higher than the 72Ω value from Booker's modified formula, but quite beneficial for coupling to high-impedance broadband devices |
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RPLAB @ gujma @ |
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736 |
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