Extension of the macroscopic model for reflection near-field microscopy: regularization and image formation

Abstract

A macroscopic self-consistent model for external-refraction near-field microscopy is extended to include the consideration of arbitrary fiber tips and the image formation of surface structures. An appropriate regularization procedure is developed to produce a stable solution of the self-consistent equation. This equation is generalized to treat the presence of a thin-layer medium with a subwavelength structure on the sample surface. Numerical results for two trapezium-shaped fiber tips are presented. This modeling confirms that the sharper tip ensures better imaging properties of the microscope but that the lateral resolution is limited by a fraction of the wavelength because of the microscopic sizes of the fiber tips.