Eigenmodes for the problem of extraordinary light transmission through subwavelength holesB. Sturman1, E. Podivilov1 and M. Gorkunov2, 3
1 Institute of Automation and Electrometry - 630090 Novosibirsk, Russia
2 Institute of Crystallography, Russian Academy of Sciences - Leninskii pr. 59, 119333 Moscow, Russia
3 Department of Mathematics, University of Strathclyde - Glasgow G1 1XH, UK
received 14 April 2007; accepted in final form 23 August 2007; published October 2007
published online 18 September 2007
We show that the widespread concept of eigenmodes in lossless waveguide structures, which assumes the presence of propagating and evanescent modes only, fails in the case of metal-dielectric structures, such as single holes/slits and periodic arrays of holes/slits in metals. In addition to these modes, there is a sequence of new eigenstates with complex values of the propagation constant and non-zero lateral energy flows. The whole eigenproblem ceases to be Hermitian because of changing sign of the optical dielectric constant. The new anomalous modes are shown to be essential for the description of the extraordinary light transmission through subwavelength holes.
42.25.Bs - Wave propagation, transmission and absorption.
42.70.Qs - Photonic bandgap materials.
73.20.Mf - Collective excitations (including excitons, polarons, plasmons and other charge-density excitations).
© Europhysics Letters Association 2007