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Bessel beam
About: Bessel beam is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 42264 citations.
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TL;DR: In this paper, the focal length and the depth of focus of the axicon lens of a polymeric microaxicon were measured, and the full width at half maximum of the beam was obtained.
Abstract: We present a quick, simple and accurate digital holographic characterization of the Bessel beams produced by polymeric microaxicons. This technique allows the numerical reconstruction of both intensity and phase of the beam at whichever point starting from a single acquired hologram. From these data, it is possible to go back to the axicon structure, and to gather information about their characteristics. In particular, the focal length and the depth of focus of the axicon lens are experimentally measured, and the full width at half maximum of the beam is obtained too. The depth of focus, very large for a Bessel beam with respect to a Gaussian one, is successfully exploited for optical trapping of micrometric objects.
49 citations
TL;DR: In this article, a radially periodic 2-D leaky-wave (LW) antenna is proposed for the generation of zeroth-order Bessel beams within a limited spatial region and over a wide-frequency range.
Abstract: A radially periodic 2-D leaky-wave (LW) antenna is studied for the generation of zeroth-order Bessel beams within a limited spatial region and over a wide-frequency range. The antenna design is wideband and based on an annular metal strip grating placed on the top of a grounded dielectric slab, supporting a cylindrical leaky wave (CLW) with a fast backward spatial harmonic. The focusing capabilities of the relevant LW aperture fields are investigated over the considered frequency range (15–21 GHz), in conjunction with the dispersion analysis of the optimized structure, which is developed by means of an efficient in-house method of moments code. Full-wave simulations using a commercial tool including a simple coaxial feeder are presented and discussed, demonstrating the desired wideband operation. The antenna design is validated by means of measurements performed on a manufactured prototype, considering different frequencies and components of the electric field within the nondiffracting range of the system. The proposed design represents an attractive simple and low-cost solution potentially able to generate arbitrary-order Bessel beams at microwaves as well as in the millimeter-wave and terahertz frequency regions.
49 citations
TL;DR: In this article, the free-space propagation of spatially localized ultrashort laser pulses is investigated based on a particular pulsed form of the well-known Bessel beam, which is termed a Bessel pulse beam.
Abstract: Free-space propagation of ultrashort pulses is investigated. Space-time couplings are reduced for a particular form of beams that is termed a pulse beam, or a type 3 pulsed beam. General conditions for the formation of pulse beams in the paraxial approximation are presented. The free-space propagation of spatially localized ultrashort laser pulses is investigated. This treatment is based on a particular pulsed form of the well-known Bessel beam, which is termed a Bessel pulse beam. The connections with focus wave modes and X waves are discussed.
49 citations
TL;DR: In this paper, a nanometer-scale fabrication on metal thin films using ablation by femtosecond laser pulses, with Bessel beam profiles, has been reported, where the laser fluence around ablation threshold allows controlling the structure size below the diffraction limit.
Abstract: We report nanometer-scale fabrication on metal thin films using ablation by femtosecond laser pulses, with Bessel beam profiles. Choosing the laser fluence around ablation threshold allows control of the structure size below the diffraction limit. We show that using Bessel beams has several advantages. Bessel beams have focal spot sizes insensitive to longitudinal position, which significantly relaxes alignment constraints. Tighter foci are easier to generate, less costly, and less prone to aberrations. Scaling the method to shorter wavelengths, and hence increasing the resolution is also straightforward. By using the proposed method, we generate structures with resolution below 200 nm.
49 citations
TL;DR: A quasi-Bessel beam (QBB) known to be nondiffracting was generated by a conical dielectric lens to detect foreign objects in food samples using the finite-difference time-domain (FDTD) method.
Abstract: Food quality monitoring, particularly foreign object detection, has recently become a critical issue for the food industry. In contrast to X-ray imaging, terahertz imaging can provide a safe and ionizing-radiation-free nondestructive inspection method for foreign object sensing. In this work, a quasi-Bessel beam (QBB) known to be nondiffracting was generated by a conical dielectric lens to detect foreign objects in food samples. Using numerical evaluation via the finite-difference time-domain (FDTD) method, the beam profiles of a QBB were evaluated and compared with the results obtained via analytical calculation and experimental characterization (knife edge method, point scanning method). The FDTD method enables a more precise estimation of the beam profile. Foreign objects in food samples, namely crickets, were then detected with the QBB, which had a deep focus and a high spatial resolution at 210 GHz. Transmitted images using a Gaussian beam obtained with a conventional lens were compared in the sub-terahertz frequency experimentally with those using a QBB generated using an axicon.
49 citations