We study numerically the interference resulting from the superposition of two Bessel beams propagating in free space. We discuss how to obtain such beams and show the existence of the self-imaging effect during propagation. The evolution of the superimposed Bessel beams is analyzed on the basis of the evolution of the individual beams. Our exact numerical predictions contradict previous approximated analytical treatments, showing that they can lead to quantitatively wrong results and misleading conclusions.

Interference of traveling nondiffracting beams

We experimentally verified the interference resulting of the superposition of two Bessel beams propagating in free space and showed for first time the self imaging effect using nondiffracting beams. Our results are supported by numerical simulations and possible applications are discussed.

Experimental observation of interfering Bessel beams

Numerical modeling of medical ultrasound has advanced tremendously in the past two decades. This opens up a great number of opportunities for medical ultrasound and associated technologies. Numerous new governing equations and algorithms have emerged and been applied to studying various medical ultrasound applications, including ultrasound imaging, photo-acoustic imaging, and therapeutic ultrasound. In addition, thanks to the rapid development of computers, modeling acoustic wave propagation in three-dimensional, large-scale domains has become a reality. This article will provide an indepth literature and technical review of recent progress on numerical modeling of medical ultrasound. Future challenges will also be discussed.

Modeling of wave propagation for medical ultrasound: a review

A flat acoustic lens to generate a Bessel-like beam.

Gain-guided modes in stimulated scattering processes with diffraction-free pump beams

The analysis is based on the Khokhlov–Zabolotskaya–Kuznetsov wave equation. Analytical and approximate solutions are derived for the second harmonic component in the Bessel nondiffracting beam. The theoretical results indicate that the second harmonic beam is nearly nondiffracting in the radial direction and the pressure amplitude is proportional to the square root of propagation distance in the quasilinear approximation, and that the beamwidth of the second harmonic is just 1/2 times that of the fundamental component in the Bessel field, not as 1/√2 times in the fields radiated by other sources.

Desheng Ding

Papers

The second harmonic component in the Bessel beam