Wide-band optical field concentrator for low-index core propagation D. de Ceglia, M. De Sario, A. D’Orazio, V. Petruzzelli, M.A. Vincenti, F. Prudenzano and M. Scalora J. Eur. Opt. Soc.-Rapid Publ., 1 (2006) 06023 Published online: 14 November 2006 DOI: 10.2971/jeos.2006.06023