Bessel beam

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

Visual alignment of mechanical structures using a Bessel beam datum: practical implementation

Abstract: We describe a visual method for aligning physically separated, large structures using a Bessel beam to define a common datum. The equipment consists of an alignment telescope, used to generate and project the optical beam, and a series of crosswire targets fitted to each structure. Alignment is achieved by eye using a loupe or CCD camera to observe superposition of the Bessel intensity structure and crosswire shadow. The method is simple and intuitive, and can be implemented on a low budget. The combination of structured beam profile and low beam divergence allows a best-case alignment accuracy of 10 microns under lab conditions for beam lengths of 19 metres, decreasing to 30-50 microns r.m.s. for field measurements. The self-regeneration property of the Bessel beam facilitates the location of multiple beam targets with negligible degradation in beam quality. Error sources include Bessel ring - target wire mismatch, target centering/ roundness errors, and air turbulence.

Three-Dimensional All-Optical Switching Using a Single Diffracting Bessel Beam

Abstract: A single Bessel beam (BB) enables the scalable optical writing of waveguide devices with multiple inputs and outputs in a nonlinear medium. For this purpose, we experimentally propagate a diffracting zero-order BB in a strontium barium niobate photorefractive crystal. Such a configuration can be used for the self-writing of complex waveguiding structures. By tailoring different key parameters such as the diffraction phenomenon through the BB size, the nonlinearity strength through the applied electric field, and the photoinduced refractive-index modulation depth through input beam intensity, our optical platform enables not only the generation of optical splitters but also an all-optical control of the output intensity levels. We also analyze the stability in space and time of the different photoinduced channels. We show that adding a background illumination onto the medium permits a steady-state photoinduced refractive-index modulation with up to nine output channels. These results enrich the research on scalable optical writing techniques for the realization of complex interconnects and enlarge further possibilities for all-optical switching.

Potential of Bessel spiral zone plate in complex beam shaping and structuring

Abstract: We aim here to show that azimuthal structuring of the optical beam may be realized by apodizing a spiral zone plate using an azimuthal-modulated Bessel function. Furthermore, we demonstrate that the azimuthal modulation of a Bessel beam may cause its transmittance to take negative values in azimuth. Accordingly, when a diffractive element (herein, spiral zone plate) is apodized by such a modulated Bessel function, its transmittance undergoes an azimuthal phase change. Consequently, the phase change is imposed on a beam passing through the element. This means that the technique enables us to produce a variety of azimuthal beam shapes, such as spiral, ring-lattice, light-arm, and multi-spot beams. In this research, we illustrate how these structures and shapes are produced and tailored. To verify the consequences of the simulation, corresponding experiments were planned.

Micro-scale Additive Manufacturing Using the Optical Potential Generated by a Bessel Beam

Abstract: In this study, we proposed a novel micro-scale additive manufacturing method based on the optical potential formed by a Bessel beam. The proposed technique is expected to show no deterioration in manufacturing resolution due to heat generation, to be applicable to various materials, and to be able to be performed in an air environment. The basic principle of the proposed method involves accumulating and stacking particles dispersed in air by using optical radiation pressure. In this paper, the trajectory of the accumulated particles was numerically estimated and experimentally observed. The numerical and experimental results agreed well; specifically, the background flow carried the particles to the optical axis of the Bessel beam, and then the particles were localized at the bottom of the optical potential valley on the substrate. Finally, a pillar structure was fabricated with polystyrene particles having a diameter of 1 μm, which indicated that the proposed technique was promising for practical applications.

Total-Variation Iterative Algorithm for Terahertz Transmission Computed Tomography

Abstract: A 3D continuous-wave (CW) terahertz computed tomography (CT) system employing a terahertz sources (IMPATT diodes) operating at 278.6 GHz is presented. To shorten acquisition time on the premise of guaranteeing the image quality, the algorithm minimizes the total variation (TV) is used to reconstruct the THz-CT results of zero order Bessel beam. With the 2D results of the samples have been also obtained.