I. Introduction
Bessel beam is a kind of nondiffraction beam with a Bessel-type intensity distribution along the radial direction. Since it is a natural solution to Helmholtz equation in free space, Bessel beam is nondiffrative, meaning the wave is not diffracting and spreading out as it propagates. It has been proven that even a practically realizable truncated Bessel beam, i.e., pseudo-Bessel beam, also features nondiffracting property and maintains a high intensity focus over a considerable distance [1]. Due to its diffraction-free and self-healing properties, Bessel beam was firstly proposed in optical region for optical manipulation, particle trapping, and nanofabrication applications [2]– [4]. It has been extended to lower microwave band with applications of directional heating, wireless power transmission and secure short-range point-to-point communications [5]– [7].