Bessel beam

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

High-contrast volumetric imaging of synapses and microcirculations with Bessel-droplet two-photon fluorescence microscopy

Abstract: Bessel foci used for two-photon fluorescence excitation have enabled high-speed volumetric imaging. At high numeric aperture, their imaging performances are compromised by substantial side-ring excitation and suffer from reduced image contrast. Here, we describe axially extended Bessel-droplet foci with suppressed side rings and more resistance to optical aberrations. Applying novel phase patterns to generate Bessel-droplet foci of variable NAs at high power throughput, we achieved continuous volume imaging by scanning them interferometrically along the axial direction. With Bessel-droplet foci, we demonstrated high-resolution volumetric imaging of synaptic anatomy and function as well as lymphatic circulations in the mouse brain in vivo.

Generation of Broadband Dual Tilted Bessel Beams with Polarization Conversion Metasurface

Abstract: In this paper, broadband dual tilted Bessel beams with the aid of a polarization conversion meta-surface is generated. The transmission meta-surface consists of 32*32 subwavelength unit cells, which can effectively convert incident linear polarized wave to zero order Bessel beam with different direction based on time reversal. The designed three-layer unit cell combining mirrored and size changed approach can meet the need of full 360° phase coverage from 10GHz to 18GHz with high transmission magnitude (>0.9). The developed dual Bessel beams propagate along the $\mathrm{e}=30^{\mathrm{o}}, \varphi=45^{\mathrm{o}}$ and $\Theta=-30_{J}\varphi=180^{\mathrm{o}}$ .And their simulated magnitude distributions in near field are provided.

Bessel beam beating-based spontaneous Raman tomography enables high-contrast deep tissue Raman measurements

Abstract: Abstract We report on the development of a novel Bessel beam beating-based spontaneous Raman tomography (B 3 -SRT) technique for depth-resolved deep tissue Raman characterization without a need of mechanical depth-scan. To accomplish B 3 -SRT, we conceive a unique method by designing a coaxial Bessel beam beating excitation scheme associated with the Bessel beam collection configuration, such that the depth-resolved Raman information is encoded by the Bessel beam beatings generated, and then the depth-encoded Raman spectra along the Bessel beam excitation region are collected simultaneously by a Bessel-shaped collection optical designed. The depth-resolved Raman spectra can be rapidly retrieved using inverse fast Fourier transform. We demonstrated the ability of B 3 -SRT technique for high contrast deep tissue Raman measurements in a highly scattering two-layer tissue phantom (e.g., fat-bone tissue model). Compared with conventional confocal Raman microscopy, B 3 -SRT provides ~ 3.7-fold improvement in deep tissue Raman detection as well as ~ 2.6-fold improvement in deeper bone tissue Raman spectral contrast in the highly scattering fat-bone tissue phantom. It is anticipated that B 3 -SRT technique developed has potential to facilitate high contrast depth-resolved deep tissue Raman measurements in biomedical systems.

Generation of Periodic Nondiffractive Beams Along Straight and Curved Trajectories Based on 3D-Printed Metasurface

Abstract: In this paper, two kinds of periodic nondiffractive beams along arbitrary trajectories, including non-accelerating and self-acceleration types, are generated by 3D-printed all-dielectric metasurfaces. The first step is to produce continuous non-accelerating and self-acceleration beams, i.e. Bessel beam and Bessel-like beams. By an appropriate modification of the conical ray pattern of the standard Bessel beams, self-accelerating Bessel-like beams can be realized. In the second step, by removing some expanding phase equivalent circles in a periodic fashion and binary modulating of the phase masks, the central main lobe of continuous beams can be modified into pulsating ones. In the third step, we construct real physical models based on the derived theories. All phase coverage can be achieved by changing the height of the proposed cube element. Therefore, the final phase distribution can be mapped to height information of each unit cell. For demonstration, several proof-of-principle metasurfaces are printed and measured, two of which are used to generate Bessel beams along different straight directions, and two of which are used to produce Bessel-like beams along C-shaped and S-shaped trajectories. In all cases, during propagation, the intensity peak alternately switches its position between the main lobe and the outing rings. Meanwhile, the measured trajectories are highly consistent with the predefined ones. The proposed metasurfaces are expected to be utilized in numerous applications like secure communication.

Coherence of vortex conic waves in turbulent atmosphere

Abstract: Theoretical research of coherent properties of the vortex conic waves propagating in turbulent atmosphere is developed. For the analysis of the analytical solution of the equation for the transverse second-order mutual coherence function of a field of optical radiation was used. The coherence radius, the normalized root-mean-square and the integral scales of a coherence degree of the vortex conic waves were considered, their dependence on parameters of optical radiation and turbulent atmosphere is analyzed. In particular, with increase in a topological charge the value of integral scale of coherence degree of a vortex conic wave beam are decreased. Preference of use for the adaptive optical systems compensating distortions of pseudo-Bessel beams in turbulent atmosphere as the gauge of distortions not a coherence radius measuring instrument such beam and a measuring instrument of integral scale of coherence degree is proved.