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Kosako, T., Kadoya, Y., & Hofmann, H. F. (2010). Directional control of light by a nano-optical Yagi–Uda antenna. Nat. Photon., 4, 312–315.
Abstract: The plasmon resonance of metal nanoparticles can direct light from optical emitters in much the same way that radiofrequency antennas direct the emission from electrical circuits. Recently, rapid progress has been made in the realization of single-element antennas for optical waves. Because most of these devices are designed to optimize the local near-field coupling between the antenna and an emitter, the possibility of modifying the spatial radiation pattern has not yet received as much attention. In the radiofrequency regime, a typical antenna design for high directivity is the Yagi–Uda antenna, which essentially consists of a one-dimensional array of antenna elements driven by a single feed element. By fabricating a corresponding array of nanoparticles, similar radiation patterns can be obtained in the optical regime. Here, we present the experimental demonstration of directional control of radiation from a nano-optical Yagi–Uda antenna composed of appropriately tuned gold nanorods.
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Novotny, L., & van Hulst, N. (2011). Antennas for light. Nat. Photon., 5(2), 83–90.
Abstract: Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa. They enable the control and manipulation of optical fields at the nanometre scale, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing. Although many of the properties and parameters of optical antennas are similar to their radiowave and microwave counterparts, they have important differences resulting from their small size and the resonant properties of metal nanostructures. This Review summarizes the physical properties of optical antennas, provides a summary of some of the most important recent developments in the field, discusses the potential applications and identifies the future challenges and opportunities.
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Novotny, L. (2007). Effective wavelength scaling for optical antennas. Phys. Rev. Lett., 98(26), 266802(1–4).
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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Saynak, U. Ä. Ÿ. (2008). Novel rectangular spiral antennas.
Abstract: 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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Kramer, B., Chen, C. - C., & Volakis, J. D. (2004). The development of a mini-UWB antenna. AMTA, , 6.
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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