Resolution of objects within subwavelength range by using the near field of a dipole

TL;DR

This paper demonstrates that using the near field of a dipole can enhance far-field resolution of objects within a subwavelength range, eliminating the need for near-field scanning techniques.

Contribution

It introduces a method to improve far-field resolution by leveraging the near field of a dipole, enabling resolution of closely spaced apertures without near-field scanning.

Findings

Resolution improves as source-aperture distance decreases.

Near field of a dipole enables resolving two close apertures in the far field.

Method eliminates the need for near-field scanning techniques.

Abstract

We analyze the far field resolution of apertures which are illuminated by a point dipole located at subwavelength distances. It is well known that radiation emitted by a localized source can be considered a combination of travelling and evanescent waves, when represented by the angular spectrum method. The evanescent wave part of the source can be converted to propagating waves by diffraction at the aperture thereby it contributes to the far field detection. Therefore one can expect an increase in the resolution of objects. We present explicit calculations showing that the resolution at the far zone is improved by decreasing the source-aperture distance. We also utilize the resolution enhancement by the near field of a dipole to resolve two closely located apertures. The results show that without the near field (evanescent field) the apertures are not resolved whereas with the near field of the dipole the far zone intensity distribution shows improved resolution. This method eliminates the requirements of near-field techniques such as controlling and scanning closely located tip detectors.