Bessel beam

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

Generation of long-distance stably propagating Bessel beams

Abstract: We put forward a new optical system, which is composed of an existing axicon doublet and a newly proposed amplitude filter. The axicon doublet consists of a positive axicon and a negative axicon with high and low refractive indices, respectively. The Bessel beam generated by the axicon doublet propagates as far as more than 200 meters, owing to a small refractive index difference between the double axicons. The newly proposed amplitude filter is used to flatten the axial intensity distribution. Numerical results calculated by the complete Rayleigh-Sommerfeld method demonstrate that the generated Bessel beam propagates stably within a very long axial range. The proposed optical system is expected to have practical applications in tracking far-distance moving targets.

Microdroplet oscillations during optical pulling

Abstract: It was recently shown theoretically that it is possible to pull a spherical dielectric body towards the source of a laser beam [Nature Photonics {\bf 5}, 531 (2011)], a result with immediate consequences to optical manipulation of small droplets. Optical pulling can be realised e.g.\ using a diffraction free Bessel beam, and is expected to be of great importance in manipulation of microscopic droplets in micro- and nanofluidics. Compared to conventional optical pushing, however, the radio of optical net force to stress acting on a droplet is much smaller, increasing the importance of oscillations. We describe the time-dependent surface deformations of a water microdroplet under optical pulling to linear order in the deformation. Shape oscillations have a lifetime in the order of microseconds for droplet radii of a few micrometers. The force density acting on the initially spherical droplet is strongly peaked near the poles on the beam axis, causing the deformations to take the form of jet-like protrusions.

Laser micromachining of transparent glass using ultrafast Bessel beams

Abstract: We fabricated optical waveguides in fused silica by focusing femtosecond laser pulses with an axicon. With this technique, we also produced microholes by using chemical etching. The axicon, which is a conical lens, generates an optical beam with a transverse intensity profile that follows a zero-order Bessel function. Bessel beams produced by axicon focusing have a narrow focal line of a few micron width which is invariant along a long distance (>1 cm). By focusing femtosecond pulses with an axicon into fused silica, we induced permanent modifications over the extented focal line of the axicon without scanning axially the glass sample. The waveguides so fabricated exhibit low losses and no detectable birefringence due their excellent circular symmetry. By translating the glass sample during the inscription process, we have fabricated planar waveguides. Microfluidic channels were obtained by soaking the exposed samples into a HF solution.

Axial radiation force of a Bessel beam on a sphere, direction reversal of the force, and solid sphere examples

Abstract: The exact solution for the axial radiation force on an isotropic sphere centered on an acoustic Bessel beam in an inviscid fluid was recently given [P. L. Marston, J. Acoust. Soc. Am. 120, 3518–3524 (2006)]. Following a review of the physical relevance of such radiation force calculations for acoustic plane waves, the Bessel beam radiation force derivation and results will be summarized. In the ordinary case, the direction of the axial force is parallel to the propagation direction of the beam. Among the predictions given in the publication is the possibility of an axial radiation force on certain fluid spheres for which the force is directed opposite to the propagation direction. In a recent extension of the published work, conditions have been identified for such a force reversal on solid spheres and elastic shells. These calculations give insight into situations where the radiation force of acoustic beams may be used to pull (instead of push) spherical objects. [Research supported in part by NASA.]

Experimental Research on Focusing Property of Radially Polarized Beam Based on Solid Immersion Lens

Abstract: Realization of a near-field optical virtual probe based on an evanescent Bessel beam is strongly dependent on a radially polarized beam; this makes it essential to study the focusing property of the beam. In this paper, two experimental setups based on a fiber device and a liquid crystal device, respectively, are built to generate a radially polarized beam. This beam and an annular radially polarized beam are focused by means of a high numerical aperture objective and a solid immersion lens (SIL). Near-field distribution of the focus spot, the evanescent Bessel field, is experimentally measured with a scanning near-field optical microscope (SNOM). The full width at half maximum (FWHM) of the central peak of the evanescent Bessel field is about 200 nm in the close vicinity of the bottom surface of SIL. This has potential for use as a near-field optical virtual probe.