Resumen: Surface electromagnetic modes supported by metal surfaces have a great potential for use in miniaturized detectors and optical circuits. For many applications, these modes are excited locally. In the optical regime, surface plasmon polaritons (SPPs) have been thought to dominate the fields at the surface, beyond a transition region comprising 3-4 wavelengths from the source. In this work, we demonstrate that at sufficiently long distances SPPs are not the main contribution to the field. Instead, for all metals, a different type of wave prevails, which we term Norton waves (NWs) for their resemblance to those found in the radio-wave regime at the surface of the Earth. Our results show that NWs are stronger at the surface than SPPs at distances larger than 6-9 SPP absorption lengths, the precise value depending on wavelength and metal. Moreover, NWs decay more slowly than SPPs in the direction normal to the surface. Idioma: Inglés DOI: 10.1088/1367-2630/11/12/123020 Año: 2009 Publicado en: New Journal of Physics 11, 12 (2009), 123020 [15 pp] ISSN: 1367-2630 Factor impacto JCR: 3.312 (2009) Categ. JCR: PHYSICS, MULTIDISCIPLINARY rank: 12 / 71 = 0.169 (2009) - Q1 - T1 Financiación: info:eu-repo/grantAgreement/ES/MICINN/CSD2007-046 Financiación: info:eu-repo/grantAgreement/ES/MICINN/MAT2008-06609-C02 Tipo y forma: Article (Published version)