Bessel beam

About: Bessel beam is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 42264 citations.

Acoustic radiation force in standing and quasi-standing high-order Bessel beams on a multilayered sphere

Abstract: The acoustic radiation force exerted by a standing and quasi-standing high-order Bessel beam on a multilayered sphere immersed in an ideal fluid is theoretically and numerically studied in this work. By means of the finite series method, the incident beam is expanded in terms of spherical harmonic functions. An analytical expression of the acoustic radiation force is derived based on the sound scattering theory. The dimensionless radiation force function versus ka is also simulated, with a particular emphasis on the relative thickness of each layer as well as the half-cone angle. To better simulate the practical manipulation, the effect of sound absorption is also analyzed. The simulated results of the first three orders reveal that the radius of each layer affects the position of peaks and dips of the curves, and acoustic trapping can be achieved at selected ka. It is also found that the curves exhibit the same general trend but the opposite directions when the order is 1 and 2, respectively. This study is expected to be useful in acoustic manipulation, drug delivery in the field of biomedical ultrasound and material sciences.

Analysis of Resonant Bessel-Beam Launchers based on Isotropic Metasurfaces

Abstract: Resonant Bessel-beam launchers are azimuthally in-variant structures characterized by a circular grounded dielectric slab with an isotropic metasurface on top. Previous works ana-lyzed the launchers performance for some specific cases, assuming TE or TM polarizations, inductive or capacitive metasurfaces, cavities with sub-wavelength or half-wavelength height. We show here with both theoretical and full-wave results that the inductive or capacitive nature of the metasurface has a fundamental role in the radiating behavior of these devices. Results are reported for the relevant TM-polarized case, considering air-filled, half-wavelength thick cavities. The extension of this analysis to the TE-polarized and dielectric-filled case will be discussed at the conference.

A millimeter-wave bessel beam launcher through the excitation of higher-order leaky modes

Abstract: We present a Bessel beam launcher based on a radial leaky-wave antenna operating at millimeter waves. With respect to a design method proposed by one of the Authors in a lower frequency range, a new approach is chosen here, as an alternative to a simple scaling of all the geometrical parameters. In order to avoid inacceptable levels of losses and possible fabrication issues due to an extremely thin substrate, our design is based on the suitable excitation of a higher-order leaky mode. Closed-form equations are derived in order to simplify the design, providing reliable values for the physical parameters once the near-field characteristics are assigned. Simulated results are shown to validate the proposed procedure.

Directional Trimming of Radiated Ultrasonic Beam Using Decentered Annular Transducer Array

Abstract: By using a decentered annular transducer array, the directional trimming of radiated ultrasonic beams is examined. In the proposed method, the number of array elements for decentering is minimized, so the decentering operation is more simplified in comparison with that in the conventional decentering method. From the results of the calculation for the examination of the aspect of the radiated beam, it is shown that the center of the generated narrow beam moves at a sound axial distance from the sound source that is determined by the actual decentered element, and that the slippage of the center of the beam is proportional to the decentering ratio of the decentered element. From these results, the directional trimming of the radiated beam is confirmed. The technique presented here is highly simplified; thus, its applicability should be high in the production of practical sound sources.

Comparison of the High-Aperture Bessel and Gaussian Beams

Abstract: The diffraction broadening of the high-aperture freely propagating (vector) Bessel and Gaussian beams is considered. The dependences of the degree of transverse concentration of light in such beams on their axial and radial coordinates are obtained. It is shown that if the initial degree of the transverse localization of total power of these beams is the same, the diffraction broadening of a Gaussian beam is smaller than that of a Bessel beam, and the only advantage of the latter is the specific radial distribution of the field amplitude.