Numerical simulation of evanescent Bessel beams and apodization of evanescent field in near-field optical virtual probe

Abstract

A near-field optical virtual probe based on the principle of near-field evanescent wave interference can be used in optical data storage, nano-lithography, near-field imaging and optical manipulation etc. The best choice of evanescent wave interference is evanescent Bessel beams that have the characteristics of both propagating Bessel beams and evanescent wave. It is concluded that evanescent Bessel beams is an evanescent wave with the characteristics of diffraction free and radial polarization. These characteristics lead to several advantages in near-field optics: the focus of radially polarized light can be quite smaller than the one of linear polarized light used commonly and diffraction free can bring in constant intensity distribution in a certain range. Meanwhile, based on the concept of conventional apodization, the idea of apodization of evanescent field is proposed to overcome some disadvantages of evanescent Bessel beams, such as the big side lobe and spread of transversal intensity. In this paper, Finite Difference Time Domain (FDTD) method is adopted to simulate the evanescent Bessel beams. Several parameters are considered as variants changeable to get the different simulation results. The better performance of the side lobe suppression and the narrow spot size are discussed. This work may be important to the application of near-field optical virtual probe in the future.