Bessel beam

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

Rapid fabrication of precise glass axicon arrays by an all laser-based manufacturing technology

Abstract: The authors report on the rapid fabrication of an axicon array, consisting of 37 individual axicons in a hexagonal arrangement, made of fused silica by an all laser-based manufacturing method within only 23 min. Therefore, a two-step process is used, first to ablate the silica substrate in a layer-by-layer process, generating the predefined geometry of the axicon array with a femtosecond laser, and second to polish the rough optical element by applying a CO 2 laser to reach smooth surfaces. Here, the roughness is reduced from 0.36 μm before to 48 nm after the polishing step, thus reaching optical quality. The finalized axicon array was placed into a femtosecond laser machine for a detailed evaluation of the resulting quasi-Bessel beams. It is found that all sub-beams exhibit the typical zeroth-order Bessel beam intensity distribution, in turn confirming that the manufacturing process used here is well suitable for the fabrication of complex optical geometries. Cross sections of the sub-beams in both x- and y-directions show an almost identical intensity profile, indicating the high contour accuracy of the axicon array. The diameter of the quasi-Bessel beams is measured to be in the range of 9.4–10.3 μm [full width at half-maximum (FWHM)], and the Bessel range in propagation direction amounts to between 8.0 mm and 8.5 mm (FWHM).

Phase Fluctuations of Optical Waves in the Case of Cone Focusing in Turbulent Atmosphere

Abstract: Statistical parameters of phase fluctuations of optical radiation with a cone-shape wavefront propagating in turbulent atmosphere are studied. The method of smooth perturbations is used for calculation of the variance of phase fluctuations of conical optical waves formed by conical and conoidal axicons. It is found that the variance of phase fluctuations of a conical optical wave in turbulent atmosphere is less than that of a plane wave and a fundamental Bessel beam. The dependence of the variance of phase fluctuations on the parameter characterizing the cone-shape wavefront of an optical wave, is of a two-scale character for both conical and conoidal axicons. A decrease in the variance of phase fluctuations in turbulent atmosphere is more typical for the conical axicon than for the conoidal. The spatial nonuniformity of phase fluctuations, known for a fundamental Bessel beam, occurs for conic optical waves as well; however, the quantitative value of the effect differs in this case.

Optical pulling force and torques on Rayleigh semiconductor prolate and oblate spheroids in Bessel tractor beams

Abstract: Optical tractor Bessel beams are gaining increased interest where a negative attractive force acting in opposite direction of wave propagation is harnessed for particle manipulation in opto-fluidics, the manufacturing of periodic composite metamaterials and other related applications. Previous works considered the spherical geometry, however, it is of some importance to develop improved models to investigate objects of more complex shapes and study the tractor beam effect on them. The aim of this work is therefore directed toward this goal, where the dipole approximation method is used to compute the optical force, spin and orbital torques on a subwavelength semiconductor spheroid illuminated by a zeroth-order Bessel vector beam. Numerical computations for the Cartesian components of the optical radiation force on prolate and oblate spheroids with arbitrary orientation are performed, with emphasis on the emergence of a negative pulling force and its dependence on the half-cone angle of the beam, the aspect ratio of the spheroid, and its orientation in space. Moreover, the Cartesian components of the spin radiation torque are computed where a negative spin torque can arise, which causes a rotational twisting effect of the spheroid around its center of mass in either the counterclockwise or the clockwise (negative) direction of spinning. In addition, the axial component of the orbital radiation torque is computed which also shows sign reversal. The results of this analysis provide a priori information for the design and development of novel optical tweezers devices and tractor beams, with potential applications in the manipulation and handling of elongated particles.

Generating Bessel beams with a tunable acoustic gradient index of refraction lens

Abstract: The Tunable Acoustic Gradient Index of Refraction (TAG) lens is shown to be an alternative method of generating Bessel beam for optical manipulation. The TAG lens exhibits a combination of tunability, optical throughput, and fast switching speed, overcoming many limitations linked with conventional Bessel beam techniques. A refractive fluid is contained within a circular piezoelectric that is driven with an AC signal to establish a periodic index of refraction in the liquid. Simple changes in amplitude or frequency of the driving signal allows for the rapid modification to the transmitted pattern. The switching speed is characterized by the time to reach a steady state pattern, which is shown to depend primarily on the viscosity of the filling liquid. Times between 300 and 2000 μs are obtained corresponding to fluids with viscosity of 640 cs and 0.65 cs respectively.

Diffraction of bessel beams on 2D amplitude gratings—a new branch in the talbot effect study

Abstract: In this paper, an analytical theory for the diffraction of a Bessel beam of arbitrary order $J_l(\kappa r)$ on a 2D amplitude grating is presented. The diffraction pattern in the main and fractional Talbot planes under certain conditions is a lattice of annular microbeams, the diameters of which depend on the grating period, the illuminating beam diameter, the number of the Talbot plane, and the topological charge $l$. For the rings near the optical axis, the latter reproduces $l$ of the illuminating beam. Experiments carried out on the Novosibirsk free electron laser at a wavelength $\lambda = 141$$\mu$m using gratings with hole diameters of down to $d \approx 2\lambda $, as well as, the numerical simulations, well support the theory. Since the Laguerre-Gaussian beams can be represented as a superposition of Bessel beams, results of this paper can be applied to the analysis of the Talbot effect with the Laguerre-Gaussian beams.