Abstract

Recently there has been a number of studies of single-layer and double-layer arrays of small resonant particles made of a noble metal. The intense interest to these structures is caused by their promising properties for near-field enhancement and subwavelength imaging applications, especially in the optical range. They have substantial advantages over the structures containing DNG (double negative) materials as they are easier in fabrication and may mitigate the problem of losses. So far the super-resolution properties were theoretically investigated only for the arrays of a finite extent. In this work we consider single-layer and multilayer infinite arrays. This formulation allows to build a highly effective algorithm and to consider both the problem of excitation of a periodic structure by a single dipole and the modal properties of the structure. The field produced by a single dipole source is effectively described by using the array scanning method, accelerated by the Ewald method. Each subwavelength sphere is represented as an electric dipole scatterer. Special attention is given to the investigation of the number of layers influence on local field enhancement and to the study of the field distribution between the layers.

Highlights

  • It is well known that there is the diffractional limit for conventional lenses based on curved surfaces

  • The field excited by a single electric dipole in proximity of an infinite periodic structure can be efficiently calculated using the array scanning method (ASM) [6,7,8,9,10,11]

  • The local field enhancement of infinite arrays of metallic nanospheres are investigated at optical frequencies, for a dipole source oriented orthogonally to the array plane

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Summary

INTRODUCTION

It is well known that there is the diffractional limit for conventional lenses based on curved surfaces. The field excited by a single electric dipole in proximity of an infinite periodic structure can be efficiently calculated using the array scanning method (ASM) [6,7,8,9,10,11]. To solve the problem of periodic excitation we use the formula which relates the dipole moment p∞ , representing a sphere at the position r , with the local electric field Eloc (r,rS ,kt ) produced by the array of sources pS,mn plus that of all the metal spherical nanoscatterers except for the reference one [4,5,12,19]. Once the solutions pl∞ , l = 1,..., N of equation (6) have been determined, the electric field at an arbitrary position r , produced by the array of exciting dipoles, phased with the transverse wavevector kt , are evaluated by. Proc. of SPIE Vol 6987 698704-4 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 08/09/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx k0a/c

LOCAL FIELD ENHANCEMENT
FIELD ACROSS LAYERS
SUBWAVELENGTH FIELD CONCENTRATION
CONCLUSION

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