21 J. N. Farahani, D. W. Pohl, H.-J. Eisler, and B. Hecht, Phys. Rev. Lett. 95 , 017402 (pages 4) (2005), URL http://link.aps.org/abstract/PRL/v95/e017402 . 22 P. Anger, P. Bharadwaj, and L. Novotny, Phys. Rev. Lett. 96 , 113002 (pages 4) (2006), URL http://link.aps.org/abstract/PRL/v96/e113002 . 23 T. H. Taminiau, F. D. Stefani, F. B. Segerink, and N. F. van Hulst, Nat Photon 2 , 234 (2008), URL http://dx.doi.org/10.1038/nphoton.2008.32 . 24 D. Pohl, Near-field Optics: Principles and Applications (World Scientific Publ., Singapore, 2000), chap. Near-field optics seen as an antenna problem, pp. 9–21. 25 J.-J. Greffet, Science 308 , 1561 (2005), http://www.sciencemag.org/cgi/reprint/308/5728/1561.pdf, URL http://www.sciencemag.org . 26 C. A. Balanis, Antenna Theory (John Wiley & Sons, Hoboken, NJ, 2005), 3rd ed. 27 K. B. Crozier, A. Sundaramurthy, G. S. Kino, and C. F. Quate, J. Appl. Phys. 94 , 4632 (2003), URL http://link.aip.org/link/?JAP/94/4632/1 . 28 P. M¨ uhlschlegel, H.-J. Eisler, O. J. F. Martin, B. Hecht, and D. W. Pohl, Sci- ence 308 , 1607 (2005), http://www.sciencemag.org/cgi/reprint/308/5728/1607.pdf, URL http://www.sciencemag.org/cgi/content/abstract/308/5728/1607 . 29 P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moerner, Phys. Rev. Lett. 94 , 017402 (pages 4) (2005), URL http://link.aps.org/abstract/PRL/v94/e017402 . 30 J. Li, A. Salandrino, and N. Engheta, Phys. Rev. B 76 , 245403 (pages 7) (2007). 31 H. F. Hofmann, T. Kosako, and Y. Kadoya, New J. Phys. 9 , 217 (2007). 32 C. F. Bohren and D. R. Huffman, Absorption and Scattering of Light by Small Particles (John Wiley & Sons, New York, 1983). 33 D. R. Lide, ed., CRC Handbook of Chemistry and Physics (CRC Press, Boca Raton, FL, 2006), 87th ed., URL http://www.hbcpnetbase.com . 34 L. Novotny, Phys. Rev. Lett. 98 , 266802 (pages 4) (2007), URL http://link.aps.org/abstract/PRL/v98/e266802 . 35 A. Al` u and N. Engheta, Phys. Rev. Lett. 101 , 043901 (pages 4) (2008), URL http://link.aps.org/abstract/PRL/v101/e043901 . 36 L. Rogobete, F. Kaminski, M. Agio, and V. Sandoghdar, Opt. Lett. 32 , 1623 (2007), URL http://ol.osa.org/abstract.cfm?URI=ol-32-12-1623 . 37 A. Mohammadi, V. Sandoghdar, and M. Agio, New J. Phys. 10 , 105015 (14pp) (2008). 14