Log-periodic optical antennas with broadband directivity |
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| Authors: | Radostin S. Pavlov Alberto G. Curto Niek F. van Hulst |
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| Affiliation: | 1. ICFO — Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860, Castelldefels (Barcelona), Spain;2. Department of Physics and Nuclear Energy, Universitat Politecnica de Catalunya, Castelldefels (Barcelona), Spain;3. ICREA — Institució Catalana de Recerca i Estudis Avançats, 08015 Barcelona, Spain;2. University of Vienna, Faculty of Mathematics, Nordbergstr. 15, 1090 Wien, Austria;3. Vorarlberg University of Applied Sciences, Hochschulstr. 1, 6850 Dornbirn, Austria;4. University of Applied Sciences Technikum Wien, Höchstädtplatz 5, 1200 Wien, Austria;11. Univ.-Clinic for Psychiatry, Innsbruck Medical University, Anichstr. 35, 6020 Innsbruck, Austria;12. Univ.-Clinic for Anesthesia, Innsbruck Medical University, Anichstr. 35, 6020 Innsbruck, Austria;2. Institute for Science and Technology in Medicine, School of Medicine, Keele University, Thornburrow Drive, Hartshill, Stoke-on-Trent ST4 7QB, UK;1. Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany;2. Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany;3. Paul Scherrer Institut, 5232 Villigen, Switzerland;1. STMicroelectronics, 850, rue Jean Monnet, F-38926 Crolles, France;2. IEMN UMR CNRS 8520, Institut d’Electronique, de Microélectronique et de Nanotechnologie, Avenue Poincaré, F-59652 Villeneuve d’Ascq, France;2. The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel |
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| Abstract: | Optical antennas offer unique possibilities for light manipulation on a sub-wavelength scale. Here, we study log-periodic antennas that exhibit broadband directivity as a result of the self-similar relation between the lengths, separations and widths of the elements. We show through numerical simulations that the log-periodic designs have a considerable potential for improvement of both directivity and operation bandwidth over classical Yagi–Uda designs. Moreover, the directivity is more robust against changes in the location of the source or detector at different antenna elements. We systematically study the influence of geometrical parameters on angular performance and local field enhancement to arrive at optimum values. Next, we demonstrate that introducing a gap in the dipole array architecture can provide at least a ten-fold enhancement of the emitted power. Finally we present an optical zigzag antenna capable of both broader spectral response and even higher directivity. |
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