Bessel beam

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

Taming the degeneration of Bessel beams at an anisotropic-isotropic interface: Toward three-dimensional control of confined vortical waves.

Abstract: Despite their self-reconstruction properties in heterogeneous media, Bessel beams are known to degenerate when they are refracted from an isotropic to an anisotropic medium. In this paper, we study the converse situation wherein an anisotropic Bessel beam is refracted into an isotropic medium. It is shown that these anisotropic Bessel beams also degenerate, leading to confined vortical waves that may serve as localized particle trap for acoustical tweezers. The linear nature of this degeneration allows the three-dimensional control of this trap position by wavefront correction. Theory is confronted to experiments performed in the field of acoustics. A swirling surface acoustic wave is synthesized at the surface of a piezoelectric crystal by a microelectromechanical integrated system and radiated inside a miniature liquid vessel. The wavefront correction is operated with inverse filter technique. This work opens perspectives for contactless on-chip manipulation devices.

Quasi-Gaussian Bessel-beam superposition: application to the scattering of focused waves by spheres.

Abstract: A superposition of zero-order Bessel beams is examined that closely resembles an idealized paraxial Gaussian beam, provided the superposition is not tightly focused. Plots compare wavefield properties in the focal region and in the far field for different values of kw(0), the product of the wavenumber k, and the focal-spot-radius w(0). The superposition (which is an exact solution of the Helmholtz equation) has the important property that the scattering by an isotropic sphere can be calculated without any approximations for the commonly considered case of linear waves propagating in an inviscid fluid. The nth partial wave amplitude is similar to the case of plane-wave illumination except for a weighting factor that depends on incomplete gamma functions. An approximation for the weighting factor is also discussed based on a generalization of the Van de Hulst localization principle for a sphere of radius a at the focus of a Gaussian beam. Examples display differences between the directionality of the scattering with the plane wave case even though for the cases displayed, ka does not exceed 2 and w(0)∕a is not less than 2. Properties of tightly focused wavefields and the partial wave weighting factors are discussed.

Axial resolution enhancement of light-sheet microscopy by double scanning of Bessel beam and its complementary beam.

Abstract: The side lobes of Bessel beam will create significant out-of-focus background when scanned in light-sheet fluorescence microscopy (LSFM), limiting the axial resolution of the imaging system. Here, we propose to overcome this issue by scanning the sample twice with zeroth-order Bessel beam and another type of propagation-invariant beam, complementary to the zeroth-order Bessel beam, which greatly reduces the out-of-focus background created in the first scan. The axial resolution can be improved from 1.68 μm of the Bessel light-sheet to 1.07 μm by subtraction of the two scanned images across a whole field-of-view of up to 300 μm × 200 μm × 200 μm. The optimization procedure to create the complementary beam is described in detail and it is experimentally generated with a spatial light modulator. The imaging performance is validated experimentally with fluorescent beads as well as eGFP-labeled mouse brain neurons.

STED super-resolution microscope based on first-order Bessel beams and adjustment method thereof

Abstract: The invention discloses an STED super-resolution microscope based on first-order Bessel beams and an adjustment method thereof. The STED microscope comprises an excitation light source, a loss light source, an excitation light beam expanding and collimation system, a loss light beam expanding and collimation system, a spiral phase plate, a Bessel beam generation system, a loss light focusing lens, a beam combining system, an object lens, a piezoelectric scanning system, a filter plate, a signal collection system and a single-photon detector. Loss light is the first-order Bessel beams and has scattering-resistant and self-healing characteristics, and great light spot form of the deep position of a sample can be maintained so that resolution of the deep area of the sample can be enhanced. Compared with a method of realizing STED super-resolution microscope deep imaging through adjusting an object lens correction ring, the method is relatively simple in experiment operation without active adjustment. Compared with a method of using a self-adaptive optical system, the experiment device is relatively simple and cheap.