Bessel beam

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

Holographic femtosecond laser integration of microtube arrays inside a hollow needle as a lab-in-a-needle device

Abstract: In this Letter, the femtosecond laser holographic two-photon polymerization (HTPP) method is adopted to rapidly realize a unique lab-in-a-needle (LIN) device by manufacturing microtube arrays inside a needle. The HTPP method is to modulate a Gaussian beam into a ring Bessel beam by a spatial light modulator (SLM) loaded with a Bessel hologram, and can fabricate microtube arrays with controllable inside diameter (1–10 μm) and designable patterns on such complex three-dimensional (3D) substrates by optimizing experimental parameters. A single LIN device can be processed by this method in about 4 min, which is not possible with traditional micronano technology and is much faster than the traditional two-photon polymerization method (at least several hours). To further demonstrate the functionality of this LIN device, a particle separation experiment is carried out. For the purpose of achieving greater functionality and integration of the on-chip system, this HTPP method provides a powerful processing method for integrating 3D functional microstructures on 3D nonplanar substrates.

Phase-front transformation of a first-order Bessel beam in Raman-resonant four-wave mixing

Abstract: We have studied the evolution of the phase front of an apertured first-order Bessel beam (J1) generated by a diffractive axicon during free-space propagation and its transformation in a Raman-resonant four-wave mixing process in hydrogen gas. It is demonstrated that the order of the phase singularity (vortex) of a Bessel beam can easily be detected by interferometry at the boundaries of the beam propagation range. With a J1 beam and a Gaussian beam at the Stokes and the pump frequencies and vice versa, anti-Stokes light is generated as a singular, conical beam. In both cases the observed phase front agrees with theoretical predictions. In particular, the transformation of the topological charge is consistent with the conservation of angular momentum.

Dynamics of accelerating Bessel solutions of Maxwell's equations.

Abstract: We investigate the propagation dynamics of accelerating beams that are shape-preserving solutions of the Maxwell equations, and explore the contribution of their evanescent field components in detail. Both apodized and nonapodized Bessel beam configurations are considered. We show that, in spite of the fact that their evanescent tails do not propagate, these nonparaxial beams can still accelerate along circular trajectories and can exhibit large deflections. Subsequently, our formulation is extended in other two-dimensional vectorial arrangements. The reported results can be useful in plasmonic and other subwavelength and near-field settings.

Fabrication and evaluation of negative axicons for ultrashort pulsed laser applications.

Abstract: We report on the fabrication and evaluation of a sharp tip negative axicon paving the way for applications in high-power ultrashort pulsed laser systems. The negative axicon is manufactured by applying a two-step all laser-based process chain consisting of ultrashort pulsed laser ablation and CO2 laser polishing finishing the component in less than 5 minutes. The finalized negative axicon reveals a surface roughness of 18 nm, fulfilling optical quality. Two measurement setups, including the ultrashort pulsed laser itself, are used to evaluate the formation of Bessel beams in detail. By applying a focusing lens behind the negative axicon, well-developed Bessel beams are generated while their lengths depend on the distance between the negative axicon and the lens. Furthermore, the diameter of the Bessel beams increase strongly with the propagation distance. By adding a second focusing lens, Bessel beams are generated at its focal position, being almost invariant of its position. Hence, the typical Bessel beam intensity distribution is observed over an entire moving range of this second lens of 300 mm. While these Bessel beams show superior quality in terms of sharp peaks with homogeneous concentric rings, only minor deviations in intensity and diameter are observed over the moving range.

Propagation of on-axis and off-axis Bessel beams in a gradient-index medium.

Abstract: Bessel beams have been increasingly used for their advantages of non-diffraction and long focal depth. In this paper, we studied the propagation of on-axis and off-axis Bessel beams in a gradient-index medium. By expressing a Bessel beam in integral form, the analytical expression of an on-axis, decentered, and tilted Bessel beam through a paraxial optical system is derived with the ABCD matrix method and Collins diffraction integral formula. Main lobe size and trajectory of the zeroth- and second-order Bessel beam are obtained, demonstrating that the Bessel beam is focused by the gradient-index medium and its main lobe trajectory is exactly the same as the corresponding geometrical ray for both the decentered and tilted Bessel beam. Effects of beam apodization are finally studied by the Fourier beam propagation method, showing that the side lobes of the Bessel beam vanish when the beam is focused inside the medium as only part of the beam enters the lens.