Bessel beam

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

Radiation torque on a sphere centered on an acoustic helicoidal (vortex) Bessel beam.

Abstract: Circularly polarized electromagnetic waves carry axial angular momentum and analysis shows that the axial radiation torque on an illuminated sphere is proportional to the power absorbed by the sphere [P. L. Marston and J. H. Crichton, Phys. Rev. A. 30, 2508–2516 (1984)]. Hefner and Marston [J. Acoust. Soc. Am. 106, 3313–3316 (1999)] proposed that a helicoidal acoustic beam (an acoustic vortex) also carries axial angular momentum and noted that absorption of such a beam should also produce an axial radiation torque. In the present work the acoustic radiation torque on a sphere centered on an acoustic helicoidal Bessel beam is analyzed and the torque is predicted to be proportional to the ratio of the power absorbed as a result of the interaction of sound with the sphere to the acoustic frequency. The torque is also proportional to the topological charge of the beam. Depending on the beam helicity, the torque is parallel or anti‐parallel to the beam axis. The analysis uses a relation between the scattering ...

Bessel-like beams generated by photonic crystal fibre

Abstract: We report a photonic crystal fibre device whose output far field resembles that of an ideal Bessel beam over a wide wavelength range. The Bessel-like beam self-heals when the central peak is obstructed.

Superfocusing of high-M2 semiconductor laser beams:experimental demonstration

Abstract: The focusing of multimode laser diode beams is probably the most significant problem that hinders the expansion of the high-power semiconductor lasers in many spatially-demanding applications. Generally, the 'quality' of laser beams is characterized by so-called 'beam propagation parameter' M2, which is defined as the ratio of the divergence of the laser beam to that of a diffraction-limited counterpart. Therefore, M2 determines the ratio of the beam focal-spot size to that of the 'ideal' Gaussian beam focused by the same optical system. Typically, M2 takes the value of 20-50 for high-power broad-stripe laser diodes thus making the focal-spot 1-2 orders of magnitude larger than the diffraction limit. The idea of 'superfocusing' for high-M2 beams relies on a technique developed for the generation of Bessel beams from laser diodes using a cone-shaped lens (axicon). With traditional focusing of multimode radiation, different curvatures of the wavefronts of the various constituent modes lead to a shift of their focal points along the optical axis that in turn implies larger focal-spot sizes with correspondingly increased values of M2. In contrast, the generation of a Bessel-type beam with an axicon relies on 'self-interference' of each mode thus eliminating the underlying reason for an increase in the focal-spot size. For an experimental demonstration of the proposed technique, we used a fiber-coupled laser diode with M2 below 20 and an emission wavelength in ~1μm range. Utilization of the axicons with apex angle of 140deg, made by direct laser writing on a fiber tip, enabled the demonstration of an order of magnitude decrease of the focal-spot size compared to that achievable using an 'ideal' lens of unity numerical aperture.

Subtraction method via phase mask enables contrast enhancement in scanned Bessel light-sheet microscopy.

Abstract: We report on the generation of a hollow Bessel beam with a hole along the direction of propagation by using an easy-to-implement phase mask and investigate its effectiveness to reduce the out-of-focus background in light-sheet fluorescence microscopy (LSFM) with scanned Bessel beams by subtraction imaging. Overlaying ${\pi }$π-phase retardation between the two equal parts of the Bessel beam across the entrance pupil of the objective lens, a hollow Bessel beam with zero intensity at the focal plane can be achieved. By optimizing the numerical aperture of the annular mask applied in the hollow Bessel beam, matched distributions of the ring system between the hollow Bessel beam and the conventional Bessel beam are achieved. By subtraction between the two LSFM images, the out-of-focus blur caused by the ring system of the Bessel beam can be significantly reduced. Comparison with conventional Bessel LSFM images exhibits a better sectioning capability and higher contrast.

Direct axial plane imaging of particle manipulation with nondiffracting Bessel beams.

Abstract: Optical manipulation with nondiffracting beams has been attracting great interest and finding widespread applications in many fields such as chemistry, physics, and biomedicine. Generally, optical manipulation is conducted in an optical microscopy system, which, in general, only allows for imaging motions of particles in the transverse plane, rendering the observation of dynamics processes occurring in the axial plane impractical. We propose and demonstrate an optical manipulation system that incorporates an axial plane imaging module. With this system, the trapping behavior in the transverse plane and the transportation process in the axial plane of a particle immersed in a Bessel beam were acquired simultaneously in real time.