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| Author |
Novotny, Lukas |
| Title |
Effective wavelength scaling for optical antennas |
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Journal Article |
| Year |
2007 |
Publication |
Phys. Rev. Lett. |
Abbreviated Journal |
Phys. Rev. Lett. |
| Volume |
98 |
Issue |
26 |
Pages |
266802(1-4) |
| Keywords |
optical antennas |
| Abstract |
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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| Author |
Saynak, UÄŸur |
| Title |
Novel rectangular spiral antennas |
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Manuscript |
| Year |
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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750 |
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Kramer, B.; Chen, C-C.; Volakis, J.D. |
| Title |
The development of a mini-UWB antenna |
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Journal Article |
| Year |
2004 |
Publication |
Measurement and Techniques Association Symposium |
Abbreviated Journal |
AMTA |
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6 |
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optical antennas; Ultra Wide Band; Spiral Antenna, Dielectric Loading |
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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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RPLAB @ gujma @ |
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751 |
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| Author |
Novotny, L. |
| Title |
The history of near-field optics |
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Manuscript |
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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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| Author |
Puscasu, Irina; Boreman, Glenn D. |
| Title |
Theoretical and experimental analysis of transmission and enchanced absorption of frequency selective surfaces in the infrared |
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Conference Article |
| Year |
2001 |
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Proc. SPIE |
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Proc. SPIE |
| Volume |
4293 |
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185-190 |
| Keywords |
optical antennas |
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A comparative study between theory and experiment is presented for transmission through lossy frequency selective surfaces (FSSs) on silicon in the 2 – 15 micrometer range. Important parameters controlling the resonance shape and location are identified: dipole length, spacing, impedance, and dielectric surroundings. Their separate influence is exhibited. The primary resonance mechanism of FSSs is the resonance of the individual metallic patches. There is no discernable resonance arising from a feed-coupled configuration. The real part of the element's impedance controls the minimum value of transmission, while scarcely affecting its location. Varying the imaginary part shifts the location of resonance, while only slightly changing the minimum value of transmission. With such fine-tuning, it is possible to make a good fit between theory and experiment near the dipole resonance on any sample. A fixed choice of impedance can provide a reasonable fit to all samples fabricated under the same conditions. The dielectric surroundings change the resonance wavelength of the FSS compared to its value in air. The presence of FSS on the substrate increases the absorptivity/emissivity of the surface in a resonant way. Such enhancement is shown for dipole and cross arrays at several wavelengths. |
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RPLAB @ gujma @ |
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753 |
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