Using the effective-index approximation we show that touching spherical metal surfaces form a broadband omnidirectional absorber of gap surface plasmons (GSP), concentrating all GSP waves travelling within a certain radius at the point of contact (at which the field intensity tends to infinity even in the presence of metal absorption) and representing thereby a two-dimensional analogue of an optical black-hole realized without use of meta materials. The developed wave analysis is supplemented with the geometrical optics (adiabatic) description providing explicit expressions for the critical radius (radius of the event horizon) and buildup of field enhancement along ray trajectories.
© 2011 Optical Society of America
Optics at Surfaces
Original Manuscript: June 30, 2011
Revised Manuscript: September 21, 2011
Manuscript Accepted: September 21, 2011
Published: November 2, 2011
Khachatur V. Nerkararyan, Sona K. Nerkararyan, and Sergey I. Bozhevolnyi, "Plasmonic black-hole: broadband omnidirectional absorber of gap surface plasmons," Opt. Lett. 36, 4311-4313 (2011)