I. Introduction
Diffraction is a fundamental phenomenon of all classical wave and also the fundamental basis of quantum-mechanical uncertainty relations [1]. For this reason, electromagnetic (EM) waves exhibit diffractive spreading along with the propagation coordinate (from the source to far field). Several years ago, Durnin [2] mentioned that there was a diffraction-free mode solution of the Helmholtz equation , where , , and is the zeroth-order Bessel function of the first kind (with ). In that case, the wave (with a Bessel profile) can theoretically propagate without incurred diffraction. Durnin et al. [1] and Durnin [2], for the first time, gave the detailed theoretical analysis, numerical simulation, and experimental demonstration of the above-cited nondiffraction wave. After that, several similar nondiffraction beams were reported, including higher order Bessel beams, Mathieu beam, and other beams based on parabolic cylinder functions [3], [4].